Atmospheric corrosion of historical organ pipes: The influence of environment and materials

Corrosion Science 50 (2008) 2444–2455

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Corrosion Science

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Atmospheric corrosion of historical organ pipes: The influence of environmentand materials

Cristina Chiavari a,*, Carla Martini a, Daria Prandstraller a, Annika Niklasson b, Lars-Gunnar Johansson b,Jan-Erik Svensson b, Alf Åslund c, Carl Johan Bergsten c

a Department of Metals Science, Electrochemistry and Chemical Techniques, Via Risorgimento 4, University of Bologna, 40136 Bologna, Italyb Department of Chemical and Biological Engineering, Chalmers University of Technology, Göteborg, Swedenc Göteborg Organ Art Center, GOArt, Göteborg University, Göteborg, Sweden

a r t i c l e i n f o a b s t r a c t

Article history:Received 14 May 2007Accepted 17 June 2008Available online 11 July 2008

Keywords:A. LeadA. Organic acidB. SEMB. X-ray diffractionC. Atmospheric corrosion

0010-938X/$ - see front matter � 2008 Elsevier Ltd. Adoi:10.1016/j.corsci.2008.06.045

* Corresponding author. Tel.: +39 (0) 51 20 93464;E-mail addresses: [email protected] (

unibo.it (C. Martini).

The corrosion of lead-rich pipes in historical organs in different parts of Europe has been investigated. Theinfluence of the environment and the composition and microstructure of the pipe metal was studied. Pipecorrosion was documented by visual inspection (boroscope). The corrosion attack and the compositionand microstructure of the metal were characterized by OM, SEM, XRD, IC and FAAS. It is shown thatthe degree of corrosion of the pipes is correlated to the concentration of gaseous acetic and formic acidin the organ. The organic acids are emitted by the wood from which the wind system is built. It is alsoshown that pipe corrosion decreases with increasing tin content in the range 0–4% (wt). Possibleconservation strategies are discussed.

� 2008 Elsevier Ltd. All rights reserved.

1. Introduction

The pipe organ and its music are important parts of the culturalheritage of Europe, which includes more than 10000 historicallyvaluable organs. A major threat to our organ heritage is harmful in-door environments. A serious corrosion attack was discovered inthe mid 1990s inside the Prinzipal 160 prospect pipes in the famousStellwagen organ in St. Jakobi Church in Lübeck (Fig. 1). The corro-sion had begun to cause cracks and holes in some of the pipes andsomething had to be done to save these invaluable pipes from 1467with such a wonderful sound. It was very important to understandhow to treat the corroded pipes and keep them from corroding fur-ther in order to set up an efficient conservation strategy. This wasthe point of departure for the EC funded COLLAPSE (Corrosion ofLead and Lead–tin Alloys of Organ Pipes in Europe) project. Animportant part of the project was to carry out a field study toachieve a deeper understanding of the corrosion problem and iden-tify the different factors that influence the emergence of pipecorrosion.

It is worth pointing out that most organ pipes are manufacturedwith a wide range of lead–tin alloys, from nearly pure lead tonearly pure tin, with many other intermediate possibilities. A pipeorgan may consist from hundreds to up to thousands of pipes, ar-

ll rights reserved.

fax: +39 (0) 51 20 93467.C. Chiavari), carla.martini@

ranged in different stops (i.e., sets of pipes with similar tone qual-ity). Recycling scrap metal is a common practice in organ buildingthat leads to the production of sheets with slightly different com-positions. Different sheets can be used to manufacture differentpipes in the same stop or different parts of the same pipe; pipesconstructed of different materials can thus be exposed to the sameenvironment because they belong to the same organ, and this sit-uation is the ideal case for studying the influence of materialparameters on corrosion behaviour.

In the present paper, the correlations among environment,material and corrosion behaviour are discussed on the basis ofthe results obtained by mapping the environment and by charac-terizing the materials of historical pipe organs selected in differentgeographical areas in Europe (‘‘field study organs”). In each area,instruments affected by corrosion have been compared to instru-ments that have not suffered corrosion to identify the factorsresponsible for corrosion.

The field studies were done in the following organs:

� Basilica di S. Maria di Collemaggio, L’Aquila, Italy, Luca Neri daLeonessa second half of the 17th century (corroded).

� Church of Madonna di Campagna, Ponte in Valtellina, Italy, M.Bizzarri 1518, Antegnati 1589, C. Prati 1657 (not corroded).

� Groene of Willibrorduskerk, Oegstgeest, the Netherlands,Metzler 1976 (corroded).

� Waalse kerk, Amsterdam, the Netherlands, C. Müller 1734 (notcorroded).

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Fig. 2. Active sampling inside an organ windchest. A Teflon tube is inserted into theorgan pallet box through a hole in the toeboard. The wind is pumped out of theorgan through a filter.

Fig. 1. (a) The Stellwagen organ in St. Jakobi Church, Lübeck, and (b) a view of thepipes on the windchest before the restoration: Prinzipal 160 pipes are in the last rowin the background.

C. Chiavari et al. / Corrosion Science 50 (2008) 2444–2455 2445

� The Koninklijk Conservatory, Brussels, Belgium, A. Cavaillé-Coll1880 (corroded).

� The Jezuietenhuis, Heverlee, Belgium, A. Cavaillé-Coll 1880 (notcorroded).

� The Stellwagen organ in St. Jakobi Church, Lübeck, Germany(corroded).

2. Experimental

2.1. Environment

The concentration of organic acids and aldehydes using activeand passive sampling was measured inside the organ pallet box,1

outside the windchest,2 in the bellows room and the church room.During active sampling inside the organ windchest, a small pipewas lifted out of the toeboard. A Teflon tube was inserted into thehole of the toeboard, see Fig. 2, down into the pallet box, and theconnection was tightened with Parafilm. The air inside the organwas pumped out of the organ through a filter that was later analysedin the laboratory. The experimental procedure has been described in

1 A part of the windchest containing the pallets (valves). Each pallet is connected toa key and, when the organist presses the key, the pallet opens and the pressurised airflows through the pipe.

2 A case containing the mechanism (pallets and channels) distributing the air to thepipes. The pipes stand on top of the windchest.

detail previously [1] and will only be mentioned briefly below. Thesemeasurements were made in collaboration with the SP Technical Re-search Institute of Sweden. Acetic acid was sampled on adsorbenttubes filled with Tenax TA. The adsorbent tubes were analysed usinga thermodesorption instrument connected to a gas chromatographand a mass selective detector. Formic acid was sampled on NaOH-coated cartridges. Cartridges were extracted with distilled water.

The solution was analysed by High Performance Liquid Chroma-tography (HPLC) in a Varian HPLC system. For active sampling,formaldehyde and acetaldehyde were sampled on Sep-pack car-tridges coated with 2,4-dinitrophenylhydrazine (DNPH). A com-mercially available passive air sampler (UMEx 100 manufacturedby SKC Inc.) was used in this study to collect aldehydes. The DNPHderivates were eluated with acetonitrile and quantified using HPLCwith UV adsorption.

2.2. Materials

The pipe corrosion was documented in written descriptions andphotos of the pipes. A boroscope (length 37.5 cm) with an attacheddigital camera was used to take photos of the inside of the pipefeet. The inside of the pipe feet was also inspected manually usingthe boroscope. When visiting an organ, the project research teamwas accompanied and supported by a person acquainted withthe organ. A number of pipes representing the corrosion statuswere removed from the organ to be documented. The corrodedpipes in the organ in St. Jakobi Church in Lübeck, the main fieldstudy organ in the project, were documented in more detail. Everypipe in the corroded Prinzipal 160 stop was carefully documentedin descriptions and photos.

Analyses were made of the composition and microstructure ofpipe metal samples and corrosion products from selected pipesin field study organs. The methodology for taking samples was de-signed to minimise both the damage of the corroded pipe and thealteration of the sample during cutting. Pipe metal samples weretaken from the foot of the most representative pipes from a corro-sion point of view in most of the field study organs. In some cases,only small amounts of material were scraped from the pipe metal(less than 20 mg) and/or corrosion products (<10 mg). The surfaceof the pipe metal samples was observed by Stereo Microscopy(SM), Optical Microscopy (OM) in bright field/reflected polarisedlight and by Scanning Electronic Microscopy (SEM) with EnergyDispersive (EDS) microprobe. Corrosion products on pipe metalsamples were analysed by X-ray Diffractometry (XRD)(Bragg-Brentano and grazing angle); localised qualitative analysisof corrosion products was carried out by EDS and IR micro-spec-troscopy in Attenuated Total Reflectance (ATR) mode on pipe metal

2446 C. Chiavari et al. / Corrosion Science 50 (2008) 2444–2455

samples, whereas samples of corrosion products consisting ofsmall amounts of scraped powders were analysed by FourierTransform Infrared Spectroscopy (FTIR) after preparation of theconventional KBr tablet. Reference spectra for IR analyses werefound in [2–5].

The amount of water soluble anions in the corrosion productlayer was determined by ion chromatography, IC (IONPAC AD9-SC Analytic Column). Glue samples were analysed by Pyrolisis–Gas Cromatography–Mass Spectrometry (Py–GC–MS).

The pipe metal samples for metallographic observations weresectioned transversally and longitudinally, cold mounted, polishedand etched to examine the microstructure [6–11]. The grain size(expressed by the grain size number G) was determined in boththe surface and cross-section of etched samples by image analysisaccording to the ASTM E1382 standard [12]. The maximum thick-ness of the corrosion layer was measured in the cross-section ofunetched samples, observed in reflected polarised light. The alloycomposition was determined by Flame Atomic Absorption Spec-troscopy (FAAS). A more detailed description of the procedures isgiven in a previous paper [13].

Field exposures of Pb and Pb–2%Sn coupons were arranged togive information on the corrosivity of the environment, with spe-cial care for the soluble anions deposited on the metal surface,and to evaluate the effect of tin alloying on lead. Polished metalsamples were exposed inside the pallet box of the organs for about4, 10 and 22 months. The coupons were hung vertically with a dis-tance of 15 mm between the samples on a metal rack.

3. Results

3.1. Environment

Both passive and active field sampling was performed. Whileboth methods provided reliable data for acetic acid, aldehydesand other VOC, only active sampling could be used in the case offormic acid. In the following, only the results obtained by activesampling are reported. The results are given in ppb (parts per bil-lion by volume = 10�9, at T = 25 oC and p = 1 atm). A high concen-tration of acetic acid vapour (approximately 700 ppb) wasdetected inside the organ windchest (pallet box) in Lübeck, to-gether with formic acid at a lower concentration (250 ppb) (see Ta-ble 1). Only traces of acetic acid were detected outside the organand in the church room, showing that the main source of the aceticacid vapour is within the organ itself. A high concentration of tol-uene (280 ppb) was detected in Lübeck, presumably emitted fromthe modern glue used for the restoration. This is explained at theend of this section. Temperature and relative humidity were mea-sured at the wind inlet and the windchest in each organ. An exam-ple is the temperature and humidity measurements in the

Table 1Concentration of acetic and formic acid vapours inside the organ pallet boxa

Corroded organ Yes (y)/No (n) Acetic acid (ppb) Formic acid (ppb)

Germany, Lübeck (y) 737 266

The NetherlandsOegstgeest (y) 1437 186Amsterdam (n) 513 149

ItalyL’Aquila (y) 191 72Ponte in Valtellina (n) 102 82

Belgiuma

Brussels (y) 818 n.a.Heverlee (n) 106 n.a.

The concentration is given in ppb (at T = 25 �C and p = 1 atm).a Only passive sampling was used. The concentration of formic acid was not

analysed (n.a.).

Stellwagen organ in St. Jakobi. The relative humidity varied fromwinter to summer between 33% and 81% and the temperature be-tween 3 �C and 26 �C.

The concentration of all organic species in the Italian organswas also higher inside the pallet box as compared to the bellowsroom and outside the windchest. The concentration of acetic acidinside the pallet box (about 200 ppb) was considerably higher inthe corroded organ in L’Aquila than in the slightly corroded organin Ponte in Valtellina, see Table 1. A very high concentration of ace-tic acid was found in the pallet box in the corroded organ inOegstgeest (about 1400 ppb). The concentration of formic acid inthe pallet box was considerably lower than the concentration ofacetic acid. The concentration of acetic acid in the pallet box inthe slightly corroded Amsterdam organ was only one-third theconcentration in the heavily corroded organ in Oegstgeest.

Only passive sampling was used in Belgium. Note that the con-centration of formic acid was not measured. A high concentrationof acetic acid (800 ppb) was found in the pallet box in the corrodedBrussels organ, see Table 1. The concentration of acetic acid wasmuch lower (100 ppb) in the slightly corroded organ in Heverlee.The concentration of acetaldehyde and formaldehyde is generallymuch lower (10–150 ppb) as compared to acetic and formic acid(70–1500 ppb) in all the organs investigated. The concentrationof formaldehyde and acetaldehyde in the organs in Belgium wasbelow the detection limit. Air pollutant concentrations in Europeanchurch environments have been reported in detail elsewhere [1].

To identify possible sources of corrosive agents, glue appliedduring the last restoration of the Stellwagen organ was taken fromthe windchest in field studies in the areas where the Prinzipal 160

pipes sit on wood (Fig. 3a). The glue from the windchest in the Stell-wagen organ was identified by Py–GC–MS as polyvinylacetate glue(so-called ‘‘white glue”, Fig. 3b). White glue samples available onthe market for organ restorers were also analysed and comparedto samples from the Stellwagen organ; they yielded similar results.

3.2. Materials

There were several positions on a pipe where corrosion could befound in the field studies:

(1) Inside the pipe foot. This is the typical corrosion damagefound in the field study. The corrosion starts in the lowerpart of the foot and moves gradually upwards in the pipetowards the mouth area, where the sound is generated. Ifnothing is done, there will be cracks and finally holes inthe foot wall of the pipe. If the corrosion reaches the pipemouth, the sound properties will gradually change and thepipe will finally be silent. This is of course very seriousbecause the historical sound quality will be lost and the cul-tural heritage of the sound of the organ will be gone forever.

(2) On the outside of the pipe where the metal is in contact withwooden parts, as on the pipe body in contact with the pipesupport or on the foot tip where the pipe stands on the toe-board. In this case, it is the acids in the wood that are indirect contact with the metal that cause corrosion.

(3) The blocks in reed pipes (see Section 3.2.4, Fig. 12). This is acommon location for corrosion damage in 19th centuryorgans. If there is a heavy attack of corrosion, the block willfinally disintegrate and must be replaced, resulting in a lossof historic material.

3.2.1. Stellwagen organ in Lübeck, GermanyAlmost all prospect pipes, originating from 1467, were cor-

roded. The documentation of the corrosion damages can be sum-marised as follows:

Fig. 3. (a) View of the windchest of the Stellwagen organ without Principal 160 pipes. Glue samples were taken from holes in the toeboard (area within dashed white lines) atthe connection between wooden boards; (b) Py–GC–MS pyrogram (at 600 �C for 15 s) of the glue from the windchest of the Stellwagen organ.


� The pipe feet with the smaller volumes were much more cor-roded than the larger ones. The corrosion in the largest pipescovered the inside surface up to a level of about 10 cm fromthe tip of the foot. The corrosion in many of the smaller pipescompletely covered the inside of the foot (all feet were about60 cm long) and had resulted in cracks, holes and deformationof the foot wall and sometimes a collapse of the foot.3

� The corrosion often reached up to a slightly higher level at theback of the pipe foot than at the front.

� There are four silent pipes (decoration pipes never played) in thefacade. Three of these were very corroded and one was not cor-roded at all. This pipe has no languid,4 resulting in a better ven-tilated open foot space.

3 ‘‘Back” and ‘‘front” with respect to the mouth of the pipe, which is an opening onthe front of the pipe.

4 The languid is a metallic disc that separates the body (upper cylindrical part) andthe foot (lower conical part) in flue pipes.

� There were mainly two types of corrosion appearances: a cor-roded surface where the corrosion products were flaking off(Fig. 4a) or where the corrosion had created a crust-like surface(Fig. 4b).

The composition of pipe metal samples from Principal 160 in theStellwagen organ is summarised in Table 2. The main componentof the alloy is Pb: most pipes consist of relatively pure lead withvery low amounts of trace elements, compared with pipes fromother field study organs. Representative images of the recrystal-lised microstructure with equiaxed twinned grains are shown inFig. 5, together with images of the cross-sections of corrosion prod-ucts observed in reflected polarised light. The grain size number inthe metal sheet ranged from 6.7 to 7.4 both on the surface and incross-section. Most of the heavily corroded pipes from Principal160 have a very low or non-detectable Sn content.

In all tested samples, regardless of the macroscopic corrosionmorphology (Fig. 4), the dominant crystalline corrosion productsdetected by XRD were hydrocerussite (Pb3(CO3)2(OH)2) and cerus-site (PbCO3) (Table 3). In addition, plumbonacrite (Pb10O(OH)6-

Fig. 5. Microstructure of sample ‘‘silent 1” from the Stellwagen organ: surface (a) and cross-section (b), etched with CH3COOH + H2O2. The bars correspond to 100 lm.

Table 2Composition of pipe metal from field study organs, wt% (FAAS)

Sn Cu Bi Sb Ag As

A5XIIf 0.17 – 0.04 – – – L’AquilaA5XIIb 0.24 0.03 – – 0.01 –A11XIIb 0.22 – – – – –

P5VIIIftn (*) – 0.02 – 0.06 – – Ponte in ValtellinaP5VIIIf (*) 0.73 0.05 – 0.19 0.02 –P7VIIIf 0.63 0.21 0.06 0.18 0.03 –P4XIIf 1.51 0.25 0.05 0.11 0.02 –P9VIIIft – 0.03 – 0.07 0.01 –

Resonator 33.7 0.15 – – 0.05 – BruxellesBlock 0.2 0.02 – – – –

VH_C# nut 0.2 0.01 0.04 – – – HeverleeVH_D# nut 3.9 0.04 0.40 – – –O_C#_block 0.1 0.01 0.05 – 0.02 –O_C# nut 3.7 0.04 0.09 – 0.08 –O_F nut 0.1 0.14 0.04 – – –O_F block 0.1 0.16 0.04 – – –

silent1_body – – – 0.14 – 0.13 Lübecksilent1_1 – – – 0.21 – 0.23silent1_2 – – – 0.15 – 0.15silent2 – 0.02 – – – –b1_original (*) – 0.02 0.05 – – –c0 0.2 0.04 – – – –c2 <0.1 0.01 – 0.11 0.05 0.30d1_original (*) – 0.01 – – – –d1_replaced (*) – 0.01 – – – –E – 0.04 – – – –h2 – 0.07 – – – –

silent1: silent pipe, far west; silent2: silent pipe, from the middle of center field.(*) Pipe with replaced foot tip.

Fig. 4. Typical corrosion appearances in the damaged and replaced feet from Principal 160 , Stellwagen organ, Lübeck: (a) flaking off and (b) crust-like surface.


Table 3Products on the inner surface of corroded pipes from the field study organs

XRD IR site

H, C H, C L’AquilaC H, C, acetates, sulphates (*) Ponte in ValtellinaH H, acetates, Pb oxides Bruxelles– H, C, Pb acetate, Pb oxides Amsterdam– H, C (Pb acetate, Pb oxides) OegstgeestH, C, Pb oxides H, C, Pb acetate Lübeck

H = Pb3(CO3)2(OH)2 hydrocerussite; C = PbCO3 cerussite; (*) = traces of solder size(bole, proteinaceous ligants).

Fig. 6. Surface morphology of corroded pipe metal from the Stellwagen organ(sample ‘‘h2”).


(CO3)6) was detected on some of the samples analysed by grazingangle XRD.

With this technique it is possible to analyse corrosion productsin very thin layers. No crystalline acetates were identified by XRD.

Fig. 7. Cross-section of corroded pipe metal (reflected polarised light): (a) sample ‘‘h2” fro

However, IR analysis (Table 3) and ion chromatography analysisshowed that acetates were present on the surface. The layer of cor-rosion products always appears to be brittle and cracked, as shownin the representative SEM image in Fig. 6. The observation made incross-section revealed that the morphology of corroded pipe metalfrom the Stellwagen organ (Fig. 7a) is similar to that of modern cor-roded organ wind conductors (Fig. 7b) with a comparable alloycomposition that were replaced because of the heavy corrosionin the past decades.

3.2.2. Italian field study organsAbout 80% of the interior pipework is corroded in the organ in

L’Aquila. Corrosion can be found inside the pipe feet, and manyof the feet have been repaired. The corrosion layer in the pipe feetis thickest at the tip of the foot and decreases further up towardsthe languid. The corrosion in some pipes has reached all the wayup to the languid and there are sometimes traces of corrosion onthe underside of the languid as well. Only very small traces of cor-rosion were found on the inside of some old pipes in the organ inPonte in Valtellina. However, a renewed foot tip was corroded (seebelow).

The composition of pipe metal samples is listed in Table 2.The main component in the alloy was Pb, with Sn ranging from0 to 1.5 wt% and Cu, Bi, Sb and Ag as the chief impurities. Pipesfrom the organ in L’Aquila were generally manufactured withlead-rich alloys containing very small amounts of impurities,whereas pipes from the organ in Ponte in Valtellina display ahigher content of tin, copper and antimony. Moreover, withinthe same organ, the composition changes from pipe to pipeand, in the case of pipe A5XII in particular, the compositionslightly also changes with the sampling point (body or foot) (Ta-ble 2).

As extensively reported in a previous paper [13], the micro-structural examination of the samples shows a completely recrys-tallised microstructure with equiaxed twinned grains with an

m the Stellwagen organ compared with (b) modern corroded organ wind conductor.

Fig. 8. Cross-section of corroded pipe metal (reflected polarised light): (a) sample ‘‘A5XIIf” from L’Aquila and (b) ‘‘P7VIIIf” from Ponte in Valtellina.


average grain size number ranging from 4 to 7.5. Pipe metal sam-ples of a rather pure lead-rich alloy display a coarse grain structure.

As regards the identification of phases in the microstructure,localised EDS analyses showed the presence of tin inclusions atgrain boundaries in the lead-rich matrix of the samples with thehighest tin content. Similarly, copper inclusions were detected inthe samples with the highest copper content. It is worth notingthat these samples have undergone localised corrosion. The roleof metal inclusions in corrosion is presently under examination.

In all samples, IR and X-ray analyses reported in the previouswork [13] show that the corrosion products consist primarily oflead carbonates (hydrocerussite and cerussite), with traces of sul-phates and lead acetates (Table 3). A sample from a corroded organpipe from L’Aquila was also analysed by ion chromatography. Largeamounts of soluble acetate were found (370 lg/cm2), togetherwith traces of formiate, chloride and sulphate (Table 4). In contrastto this, only traces of anions were detected on the uncorroded or-gan pipe from Ponte in Valtellina.

Representative images of cross-sections of the other pipes areshown in Fig. 8: the sample from L’Aquila is covered with a thickand extensive layer of corrosion products, while the sample fromthe uncorroded organ in Ponte shows a localised and unevengrowth of corrosion products. No corrosion products were visible

Fig. 9. (a) Repaired pipe from the organ in Ponte in Valtellina: view of the foot with th(‘‘old”) and the replaced (‘‘new”) metal sheet.

in the cross-section of pipe sample P4XIIf, characterized by thehighest amount of tin in the alloy (Table 2). A particular and inter-esting case is shown in Fig. 9, of pipe P5VIII from the organ in Pontein Valtellina. In this pipe, the foot tip consists of two differentmaterials soldered together during restoration (Fig. 9a). The lowerpart of the tip (sample P5VIIIftn) was added in 1994 and consists ofpure lead, whereas the upper part (sample P5VIIIf) is the originallead–tin alloy (0.73% Sn) from the 16th century. In this case, it isevident that the new part of the foot tip is covered with corrosionproducts, mainly below the solder seam, while the ancient part(‘‘old”) does not seem to be significantly affected by corrosion.

3.2.3. Dutch field study organsCorrosion was found inside the pipe feet of Quint 30 in the

Oegstgeest organ. The corrosion starts inside the foot tip and prop-agates about half way up in the foot towards the mouth area. Theouter surface of the foot tip is also corroded where the metal is incontact with the toeboard. The organ in Waalse kerk was selectedas an uncorroded organ. However, some corrosion was found in-side the pipe foot of some of the pipes in Prestant 80 in the pedaldivision.

Pipe metal from Dutch field study organs were analysed byX-ray Fluorescence (XRF) at ICN (Instituut Collectie Nederland):

e replaced tip and (b) detail of the internal surface of the foot showing the original

Table 4Water soluble anions detected by ion chromatography on: (a) pure lead coupons exposed inside the organ pallet box for a period of approximately 20 months, (b) Pb–2%Sncoupons and (c) pipe metal samples taken from the foot of the most representative pipes from the point of view of corrosion

Church Water soluble acetate(CH3COO�) (lg/cm2)

Water soluble formiate(HCOO�) (lg/cm2)

Water soluble chloride (Cl�)(lg/cm2)

Water soluble sulphate (SO�4 )(lg/cm2)

L’Aquila (corroded organ)(a) Exposed pure lead coupon 43 62 0.1 b.d.(b) Exposed Pb–2%Sn alloy coupon 0.0005 0.89 0.08 0.23(c) Sample from corroded organ

pipe372 5 12 6

Ponte in Valtellina (non-corroded organ)(a) Exposed pure lead coupon 14 36 b.d. b.d.(b) Exposed Pb–2%Sn alloy coupon b.d. b.d. b.d. b.d.(c) Sample from organ pipe

without corrosion6 2 6 8

Please note that the results are only semi quantitative.b.d. = below detection limit.

Fig. 10. Corroded block from the Conservatory organ in Brussels with a fragment ofthe resonator still attached at the top. Arrows indicate local values of Sn contentanalysed by FAAS (for more detail see Table 2).

Fig. 11. Back scattered electron (BSE) image of the cross-section of the block fromthe Conservatory organ in Brussels.


the Sn content in both samples was relatively low (0.9 wt% in Q3Hand 0.4 wt% in Prestant 80). In this case, only small amounts of cor-rosion products in the form of scraped powders (about 5–10 mg)were taken from the inner surface of the foot in selected pipes.IR spectroscopy and XRD (Table 3) showed that, also in this case,corrosion products mainly consist of lead carbonates (hydrocerus-site and cerussite): traces of lead acetates and oxides weredetected in all the samples, but these compounds were more evi-dent in sample Prestant 80 from Amsterdam than in Q3H fromOegstgeest.

3.2.4. Belgian field study organsIn the Conservatory organ in Brussels, corrosion was found on

the blocks in reed pipes. The corrosion attack is unequally distrib-uted between the pipes. Some blocks have a clean metal surfacewithout any corrosion while other blocks are heavily corroded.One block even had to be replaced because of the corrosion dam-age (Fig. 10). The organ in the Jezuietenhuis, Heverlee, was selectedas an uncorroded organ. However, there were also some corrodedblocks in this organ. Fig. 11 shows two reed pipes, one corrodedand the other without any traces of corrosion. These pipes standside by side on the windchest and are exposed to the same envi-ronmental conditions.

In the case of the Belgian field study of organs with corrodedreed pipes, only small amounts of corrosion products in the formof scraped powders and metal shavings were removed from nutsand blocks in selected pipes. Care was taken to obtain the pipe me-tal from the uncorroded core. The composition of pipe metal sam-ples is listed in Table 2.

Although the composition of pipe metal changes from pipe topipe, and sometimes also within the pipe itself (e.g. from body tofoot in flue pipes, from nut to block in reed pipes), the chemicalcomposition of all the selected pipes generally corresponds tolead-rich alloys. The maximum tin content found in these alloysis about 4 wt%, with the exception of the organ in the Conservatoryof Brussels, where the fragment of resonator on the block containsthe highest amount of tin: about 34 wt%. Trace amounts of Bi werefound in all pipes from Heverlee; Ag traces were present only inOboe c# (both in the nut and the block) from Heverlee (Table 2).

The differences in composition between the block and the frag-ment of resonator from the Conservatory organ in Brussels (Fig. 10)can be seen in greater detail in the cross-section in Fig. 12 (a cross-section was cut from this sample only because the corroded blockhad been completely replaced). Three different components can beidentified in this back-scattered electron image (SEM): the block,the soldering material and the fragment of sheet (resonator). Theblock consists of nearly pure Pb, while the sheet is rich in Sn. Theblock and resonator have been soldered with the conventional sol-

dering material for organ pipes, i.e. lead–tin eutectic alloy (Sn–38%Pb, [14]), as shown by EDS analysis. It is illustrated in Figs.10 and 11 that the layer of corrosion products on the surface ofthe blocks is always discontinuous, brittle and cracked. The IRand XRD analyses showed that corrosion products consist chieflyof lead carbonates (hydrocerussite and cerussite), with traces oflead acetates (Table 3). It is also worth noting in this case that

Fig. 12. Vox Humana pipes (D# on top, C# below) from the organ in Jezuietenhuis in Heverlee. Arrows indicate local values of Sn content analysed by FAAS (for more detail seeTable 2).


the corrosion behaviour varies with the alloy’s tin content in sam-ples collected from the same organ, i.e. exposed to the same atmo-sphere. For example, the comparison between the blocks of thetwo reed pipes from the previously mentioned organ in Jez-uietenhuis shows that the uncorroded blocks contain 3.9 wt% tin,whereas the other block, covered with a white crust of lead carbon-ates, contains only 0.2 wt% tin (Fig. 11). In the block from the Con-servatory organ in Brussels (Fig. 10), only the surface is heavilyaffected by corrosion, while neither the soldering material northe fragment of resonator were corroded. These retained a brightmetallic appearance.

3.2.5. Exposures and analysis of metal couponsThe analysis of the soluble anions in the water leached from the

real organ pipe samples and the coupons exposed in the fieldshows a similar trend. This trend is that more acetate and formi-ates were present on the samples from churches, where we alsosaw the highest concentrations of the acids in the air, see Table 4.

Results from the slightly corroded and heavily corroded organsin Italy are presented in Table 4 as an example. The analysis ofwater soluble anions from the exposed metal coupons in the cor-roded L’Aquila organ shows significant amounts (40–60 lg/cm2)of acetate and formiate on pure lead, while the amounts detectedon the Pb–2%Sn alloy were much smaller (less than 1 lg/cm2),see Table 4. In addition, small amounts of chlorides and sulphateshad accumulated on the sample surface. As mentioned in Sections3.2.1 and 3.2.2, large amounts of soluble acetates were also foundon the ancient corroded pipes from Lübeck and L’Aquila. In con-trast, the amount of water soluble anions on metal coupons ex-posed in Ponte in Valtellina was much lower (10–30 lg/cm2).The dominant crystalline corrosion products on the lead couponswere hydrocerussite and lead formiate hydroxide (Pb(HCOO)OH).No crystalline acetates were identified. However, as noted above,ion chromatography shows that acetates are present on the sur-face. No crystalline corrosion products were found on any of thePb–2%Sn alloy coupons, the surfaces being shiny after up to 22months of exposure. A comprehensive presentation of the resultsin the field coupons is given elsewhere [1].

4. Discussion

Corrosion primarily affects the inner surface of the foot in lead-rich flue pipes or the surface of the nut and block under the boot inreed pipes. Samples are chiefly covered with lead carbonates,which are most commonly found as corrosion products on samplesof lead exposed in the field in atmospheres containing organiccompounds [15–20]. Acetates and formiates are also present on

the surface. The layer of corrosion products is always crackedand non-adherent and therefore non protective. The extent of cor-rosion appears to be strictly dependent on both the concentrationof organic compounds in the organ environment and the chemicalfeatures of the pipe material.

As regards the influence of environmental features on corrosionbehaviour, pipes from field study organs where high concentra-tions of organic acid vapours have been detected, such as the or-gans in Oegstgeest (The Netherlands) and Lübeck (Germany), aremore affected by corrosion than pipes from organs with lower or-ganic acid concentrations, such as the organ in Ponte in Valtellina(Italy). Corrosion and concentration of organic acids in the atmo-sphere inside the organs thus appear to be directly correlated.

However, organs that were selected as uncorroded references(such as the organ in Ponte in Valtellina) display non negligibletraces of corrosion. Metal coupons exposed in the wind systemsprovide a further measure of the relative corrosivity in the organs.A comparison of coupons exposed in the slightly corroded andheavily corroded organs in the Netherlands and Italy, shows thatthe amount of accumulated acetate and formiate is consistentlygreater in the more corroded organs. In summary, the high concen-tration of organic acid vapours present in the wind systems of thecorroded organs and the tendency for acetate and formiate to accu-mulate on the lead coupons indicate that the two organic acidsplay an important role in the corrosion of the organ pipes.

The influence of acetic and formic acid on the atmospheric cor-rosion of lead was previously investigated in the laboratory usingpollutant concentrations (170–1100 ppb) in the same range aswas found in the present field study [19,20]. It is reported thatthe atmospheric corrosion of lead is strongly accelerated by tracesof acetic acid and formic acid vapour, the mass gain being linearwith time and pollutant concentration. A continuous depositionof acetic acid was found to be necessary to sustain the corrosionprocess. When lead is exposed to humid air with traces of aceticacid vapour, the acidification of the surface electrolyte results indissolution of the native PbO film. This triggers an electrochemicalcorrosion process that generates lead ions and hydroxide ions, pro-ducing fresh lead oxide. The corrosion product formed in the pres-ence of acetic acid vapour is a mixture of lead acetate oxidehydrate (Pb(CH3COO)2 � 2PbO � H2O), plumbonacrite (Pb10O(OH)6-(CO3)6), massicot (b-PbO) and litharge (a-PbO).

That the concentration of acetic acid is consistently much high-er in the wind system compared to the church room implies thatacetic acid is generated within the wind system itself. The windsystems (windtrunks and windchests) are mainly made of woodand it is well known that wood emits acetic acid [21]. It is likelythat the reason for the relatively low acetic acid concentration in

Fig. 13. Comparative estimation of the expected organic acid concentrations in the Principal 160 pipe feet from the largest E pipe to the smallest c3 pipe.


the Italian organs is the difference between the organ building tra-dition in Italy and that in northern Europe. In the Italian tradition,the wooden parts in the organs are usually made of white poplarand walnut which emit lower amounts of organic acids as com-pared to high emitting oak that is used in northern Europe. In gen-eral, there is an obvious risk of creating a corrosive environment ifnew wood is introduced into an old organ during a restoration.

Another factor that must be taken into account as a source ofacetic acid vapours is the type of glue used in organ repair or man-ufacture. In fact, the glue found in the windchest of the Stellwagenorgan in Lübeck, introduced in the last restoration (1977–1978),has been identified as polyvinylacetate (PVA) glue, so-called‘‘white glue”. Polyvinylacetate is a polymer of vinyl acetate: thispolymer undergoes degradation in the presence of light and water(hydrolysis), thus forming acetic acid [22]. The environmental ef-fects of the use of PVA-based adhesives in museum storage anddisplay cases have been addressed by many workers in the fieldof preventive conservation, and the use of these materials hasnot been encouraged since they emit organic acids [23–25]. Thus,in the case of the Stellwagen organ, the introduction of PVA gluetogether with the use of new wood for the toeboards5 during thelast restoration might have contributed to increasing the corrosivityof the environment of the organ. Actually, the similar morphology ofthe corroded pipe metal from the Stellwagen organ (Fig. 7a) and themodern organ wind conductors (Fig. 7b), with a comparable alloycomposition, suggests that the Stellwagen pipes might also havebeen heavily attacked by corrosion mainly in the last decades, as aconsequence of a change in the organ environment. It must also benoted that the restoration report issued in the late 1970s did notdescribe corrosion damages in the Prinzipal 160 pipes beforerestoration.

Other factors connected to the structure of the organ must beconsidered to be able to understand the corrosion behaviour. Thetoeboard for the prospect pipes in the Stellwagen organ, for exam-ple, is made of untreated, new oakwood. This oakwood is not old; itwas installed at the restoration of the organ in 1977–1978. Thereare two different situations in which the organic acids could enterinto the pipe foot: ‘‘the sound situation” when the pipe is played,where the wind containing the acids will flow through the foot;and ‘‘the silent situation” when the pipe is not played, where theorganic acids emitted from the wall in the toeboard hole underthe pipe slowly enter into the foot through the foot hole. It is dif-

5 The pipes stand on a piece of wood, the toeboard, constituting the top part of thewindchest. Holes are drilled in the toeboard, one per pipe, leading the wind into thepipe foot.

ficult to estimate the extent to which the first or the second situa-tion contributes to the corrosion situation, but it is probably acombination of both.

However, the fact that a pipe spends most of its time not beingplayed and that several of the silent facade pipes in St. JakobiChurch were very affected by corrosion indicates that ‘‘the silentsituation” may play a major role in the corrosion attack. Holes werealso drilled in the toeboard under the silent pipes. Assuming that‘‘the silent situation” gives the major contribution to the organicacids in the pipe foot, it is possible to estimate the relative levelof concentration of organic acids in the pipe feet by calculatingthe wall area of the toeboard hole (being proportional to the emis-sion quantity) divided by the foot volume. Fig. 13 shows the resultsfor all facade pipes from the largest to the smallest. The tendencycoincides very well with the observations of corrosion where thesmaller pipes are much more corroded than the larger pipes.

Finally, with regard to the influence of material features on cor-rosion behaviour, the alloy composition has been considered first.Tin is present in many samples as an alloying element; most of thesamples from Ponte in Valtellina contain more tin than samplesfrom L’Aquila (Italy). In samples from Ponte in Valtellina, all ex-posed to the same atmosphere, the thickness and the coverage ofthe surface by corrosion products appear to decrease with increas-ing tin content in the alloy. It is worth noting however that, in thecase of different atmospheres and comparable tin content, environ-mental features are the dominant factor. In fact, a comparison ofthe low-tin pipe samples in the two different environmentsshowed that only a very small amount of corrosion productsformed in Ponte in Valtellina, whereas the sample from L’Aquilais extensively corroded.

Samples from Belgian field study organs confirm the effect ofcomposition on corrosion: pipes in the same organ, even in thesame stop, exposed to the same atmosphere, displayed differentcorrosion behaviour as a function of Sn content. Different parts ofthe same pipe that consists of different materials show that thelower the Sn content, the higher the extent of corrosion. The setof pipe metal samples from Principal 160 in the Stellwagen organin Lübeck also confirmed that pipes consisting of nearly pure Pbare badly affected by corrosion. An exception is an uncorrodedlead-rich pipe, where the absence of languid leads to better venti-lation and a larger foot volume, which in turn gives a lower con-centration of organic acids in the pipe foot. This again points outthe role of organic acids as corrosive agents.

The influence of tin content on corrosion behaviour was also ob-served on the field exposed lead coupons. In marked contrast to thepure lead samples, IC analysis of the Pb–2%Sn alloy metal coupons


after exposure in the organs showed only traces of acetate andformiate on the surface (Table 4). The Pb–2%Sn coupons appeareduncorroded after exposure at optical inspection.

The beneficial effect of tin alloying is also in accordance with re-cently reported laboratory studies made in an acetic acid environ-ment [1] that show that a lead/tin alloy with 0.56% tin exhibitedhalf the mass gain at 60% RH compared to pure lead. It is suggestedthat the beneficial effect on atmospheric corrosion of alloying withtin is explained by the formation of a protective surface layer, verylikely consisting of tin oxide. It is suggested that the alloy surfacebecomes enriched in tin, which is known to be highly resistant tocorrosion attack by organic acids. The inhibitory effect of tin alloy-ing on the oxidation of lead is reported in the literature [26,27], butthe mechanism of this action is still not well understood. Furtherwork on this subject is in progress in our laboratories.

From a microstructural point of view, all the samples from fluepipes display a recrystallised microstructure with equiaxedtwinned grains, thus making it impossible to correlate the mor-phology of crystalline grains to the corrosion behaviour. This kindof microstructure is the result of the recrystallising behaviour oflead [28], since all flue pipes consist of lead-rich sheets that havebeen manufactured by plastic deformation (rolling/hammering,folding). Moreover, there is also no clear relationship betweenthe grain size and the corrosion behaviour. This is probably be-cause grain boundary effects are of minor importance in thestress-free situation of a recrystallised, equiaxed structure, wherethe main microstructural factor that influences corrosion is likelyto be intergranular precipitation [29]. In fact, inclusions in thegrain structure, such as Cu inclusions (which precipitate at grainboundaries because of the low solubility of this element in thelead-rich matrix [30]) might also promote localised corrosion[17,31]. As an example, sample P7VIIIf (Cu: 0.21 wt%) in Ponte inValtellina is more corroded than P5VIIIf (Cu: 0.05 wt%) and dis-plays localised corrosion attacks in areas corresponding to Cuinclusions, as discussed in a previous paper [13].

Sample P5VIIIft is also a special case for another reason: in thispipe, the composition of the alloy in the restored foot tip is differ-ent from that of the original alloy. Since the two different materialsare placed in contact, the modern alloy, with a lower tin contentand no protective natural patina, corroded preferentially. Thedependence of corrosion on metal composition must also be takeninto account in selecting materials for pipe repair when the foot tiphas to be replaced during restoration.

Both laboratory and field study results from the COLLAPSE pro-ject show that a preventive approach such as changing the envi-ronment is the best conservation strategy for historical organpipes. A comparative evaluation was made of the protective perfor-mance of surface treatments for lead during the project [32]. Theresults indicated that none of the tested treatments guaranteeslong term protection. Therefore, methods to effectively decreasethe emission of volatile organic compound in the organ are sug-gested. Surface treatments using substances that react to neutral-ize the acids may prove useful in reducing emission of organicacids from wood already present in an organ wind system. Workis in progress.

5. Conclusions

The present study shows that the degree of corrosion of lead-rich pipes in historical organs in different parts of Europe is corre-lated both to the concentration of gaseous acetic and formic acid inthe organ and to the composition of the pipes. It is concluded thatthe wooden parts of the wind system, i.e. windtrunk and wind-chest, are major sources of organic acid vapours, but polyvinylace-tate (PVA) glue is also an important source for acetic acid. The

corrosion product mainly consisted of lead hydroxy carbonate(hydrocerussite) and lead carbonate (cerussite), together withsome acetate. In each environment the Sn content of the alloy isa key factor for pipe corrosion. It is shown that pipe corrosion de-creases with increasing tin content in the range 0–4 wt%. The re-sults imply that there is a severe risk of creating a corrosiveenvironment with the introduction of new wood or polyvinylace-tate glue into an old organ during restoration or repair work. Theidentification of the environmental parameters and material prop-erties that are decisive for the corrosion of organ pipes may helpfind organs that are in danger of suffering severe corrosion. It willalso serve as a starting point for the formulation of new conserva-tion strategies.

Acknowledgments

COLLAPSE is a research project supported by the EuropeanCommission under the Fifth Framework Programme that contrib-utes to the implementation of the Key Action ‘‘The City of Tomor-row and Culture Heritage” within Energy, Environment andSustainable Development. The authors wish to thank organbuildersand restorers Mr. Marco Fratti (Campogalliano, Italy), Mr. RiccardoLorenzini (Montemurlo, Italy), Mr. Henk van Eeken (the Nether-lands), Mr. Patrick Collon (Belgium) and Mr. Luk Bastiaens (Bel-gium) for their help and advice. Ms. Chiara Dinoi, formerly at theUniversity of Bologna and now at the University of Toulouse(France), is gratefully acknowledged for her important contributionto this research.

Dr. Peter Hallebeek at ICN, Amsterdam (NL), is gratefullyacknowledged for XRF analysis of pipe metal from Dutch organs.Prof. Giuseppe Chiavari, University of Bologna (Italy), is gratefullyacknowledged for the Py–GC–MS analyses of the glue samples to-gether with Prof. Giorgio Poli, DIMA, University of Modena (Italy),for discussions of experimental data and Dr. Andrea Tombesi ofCIGS, University of Modena (Italy), for FTIR and micro-IR analyses.Dr. Sarka Langer and her research group at the SP Technical Re-search Institute of Sweden are thanked for a great collaboration.

References

[1] A. Niklasson, Atmospheric Corrosion of Historic Lead Organ Pipes, LaboratoryInvestigations and Field Studies, Doctoral Thesis, Department of Chemical andBiological Engineering, Chalmers University of Technology, Göteborg, Sweden,2007.

[2] K. Nakanishi, P.H. Salomon, Infrared Absorption Spectroscopy, Emerson AdamsPress, 2000.

[3] C. Degrigny, Nouvel examen des résultats d’analyses par diffraction R.X. etspectroscopie infra-rouge effectués à l’E.N.S.C.P. (1ère tranche), ProgrammePlomb – Report ARC’ Antique Nantes, France (1995).

[4] C. Giangrande, Identification of bronze corrosion products by infraredabsorption spectroscopy, recent advance in the conservation and analysis ofartefacts, in: Jubilee Conservation Conference, London, University of London,UK, 1987, pp. 135–148.

[5] M. Matteini, A. Moles, C. Lalli, Infrared spectroscopy: a suitable tool for thecharacterization of components in bronze patina, in: Seventh Triennal MeetingICOM CC, Copenhagen, September 10–14, 1984, 82/22/18–82/22/24.

[6] C. Di Martini, Lead and Lead Alloys: Metallographic Techniques andMicrostructures, Metallography and Microstructures, ASM Handbook, vol. 9,ASM International, Materials Park, OH, USA, 1999.

[7] D.A. Scott, A note on the metallographic preparation of ancient lead, Studies inConservation 41 (1996) 60–61.

[8] D.A. Scott, Metallography and Microstructure of Ancient and Historic Metals,The Getty Conservation Institute, Los Angeles, CA, USA, 1991.

[9] J. Yewko, D. Marshall, Lead: metallography made easy, Advanced Materials andProcesses 2 (1998) 22–23.

[10] Jeon Seog Kim, Min Sik Kang, Sung Bo Lee, Recrystallization during thediscontinuous precipitation of Sn in 95Pb–5Sn and 85Pb–15Sn solder alloys,Scripta Materialia 38 (11) (1998) 1677–1678.

[11] H.L.J. Pang, K.H. Tan, X.Q. Shi, Z.P. Wang, Microstructure and intermetallicgrowth effects on shear and fatigue strength of solder joints subjected tothermal cycling aging, Materials Science and Engineering A 307 (2001) 42–50.

[12] Standard Test Methods for Determining Average Grain Size UsingSemiautomatic and Automatic Image Analysis, E1382-97, American Societyfor Testing and Materials, Annual Book of ASTM Standards, 1997.


[13] C. Chiavari, C. Dinoi, C. Martini, G. Poli, D. Prandstraller, Influence ofmicrostructure and composition on corrosion of lead-rich organ pipes, in: P.Dillmann, P. Piccardo, H. Matthiesen, G. Beranger (Eds.), Corrosion of HeritageArtefacts, European Federation of Corrosion, Book No. 48, 2007, pp. 352–367.

[14] ASM Handbook, vol. 3, Alloy Phase Diagrams, ASM International, MaterialsPark, OH, USA, 1999, p. 335.

[15] T.E. Graedel, Chemical mechanisms for the atmospheric corrosion of lead,Journal of the Electrochemical Society 141 (4) (1994) 922–927.

[16] A.R. Cook, R. Smith, Atmospheric corrosion of lead and its alloys, in: W.H. Ailor(Ed.), Atmospheric Corrosion, John Wiley and Sons, London, UK, 1982, pp. 393–404.

[17] C. Degrigny, Etude de la dégradation des objects en plomb dans les collectionspubliques et des moyens de les stabiliser et de les conserver à long terme,Programme Plomb – Final Report, ARC’Antique, Nantes, France (1997).

[18] P. Mattias, G. Maura, G. Rinaldi, The degradation of lead antiquities from Italy,Studies in Conservation 29 (1984) 87–92.

[19] A. Niklasson, L.-G. Johansson, J.-E. Svensson, Nature science, Journal of theElectrochemical Society 152 (12) (2005) B519–B525.

[20] A. Niklasson, L.-G. Johansson, J.-E. Svensson, Atmospheric corrosion ofhistorical organ pipes: influence of acetic and formic acid vapour and waterleaching on lead, in: J. Ashton, D. Hallam (Eds.), Proceedings of Metal 2004,Triennial Metals Conservation Conference, Canberra, Australia, 10/2004,National Museums of Australia, Canberra, 2004, pp. 273–280.

[21] P.C. Arni, G.C. Cochrane, J.D. Gray, Emission of corrosive vapours by wood. I.Survey of the acid-release properties of certain freshly felled hardwoods andsoftwoods, Journal of Applied Chemistry 15 (1965) 463–468.

[22] N. Grassie, The thermal degradation of polyvinyl acetate. I. Products andreaction mechanism at low temperatures, Transactions of Faraday Society 48(1952) 379–387.

[23] W.A. Oddy, An unsuspected danger in display, Museums Journal 73 (1973) 27–28.

[24] S.M. Blackshaw, V.D. Daniels, Selecting safe materials for use in display andstorage of antiquities, in: ICOM Committee for Conservation Preprints of theFifth Triennial Meeting, Zagreb, 1978, 23/2/1–23/2/9.

[25] J.L. Down, M.A. MacDonald, J. Tétrault, R. Scott Williams, Adhesive testing atthe Canadian Conservation Institute – an evaluation of selected poly(vinylacetate) and acrylic adhesives, Studies in Conservation 41/1 (1996) 19–44.

[26] P. Simon, N. Bui, N. Pebere, F. Dabosi, L. Albert, Characterisation byelectrochemical impedance spectroscopy of passive layer formed on lead–tinalloys in tetraborate and sulphuric acid solutions, Journal of Power Sources 55(1995) 63–71.

[27] P. Simon, N. Bui, N. Pebere, F. Datosi, In situ redox conductivity, XPS andimpedance spectroscopy studies of passive layers formed on lead–tin alloys,Journal of Power Sources 53 (1995) 163–173.

[28] A.W. Worcester, J.T. O’Reilly, Lead and lead alloys, Properties and Selection:Nonferrous Alloys and Special-Purpose Materials, ASM Handbook, vol. 2, ASMInternational, Materials Park, OH, USA, 1999.

[29] R.D. Prengaman, Structural control of non-antimonial lead alloys via alloyadditions, heat treatment and cold working, in: Pb80, Edited Proceedings ofthe Seventh International Lead Conference, Lead Development Association,London, UK, 1980.

[30] D.J. Chakrabarti, D.E. Laughlin, Copper–lead binary phase diagram, in: AlloyPhase Diagrams, ASM Handbook on CD-ROM, vol. 3, ASM International and theDialog Corporation, 1999.

[31] C. Degrigny, R. Le Gall, Conservation of ancient lead artifacts corroded inorganic acid environments: electrolytic stabilization/consolidation, Studies inConservation 44 (1999) 157–169.

[32] C. Chiavari, C. Martini, G. Poli, D. Prandstraller, Conservation of organ pipes:protective treatments of lead exposed to acetic acid vapours, in: J. Ashton, D.Hallam (Eds.), Proceedings of Metal 2004, Triennial Metals ConservationConference, Canberra, Australia, 10/2004, National Museums of Australia,Canberra, 2004, pp. 281–293.

Atmospheric corrosion of historical organ pipes: The influence of environment and materials

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