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Factores significativos en el proceso de desgaste de acero API 5L X65 por erosión-

corrosión en el transporte de relave de cobre – Estudio experimental

Dr.-Ing. Magdalena Walczak, PhD(c) Javiera Aguirre

Pontificia Universidad Católica de ChileEscuela de IngenieríaVicuña Mackenna 4860Macul, Santiago, ChileTel. +562 2354 4229Email: [email protected]

CORROMIN, July 2017, Magdalena Walczak & Javiera Aguirre

o The problem of erosion-corrosion (E-C)o Experimental testing methodso Case study: API 5L X65

– General survey of factors– Effect of Cu2+ content on E-C contributions

Agenda

What is erosion-corrosion?


Chuquicamata mine

Sourc

e:

ww

w.p

anora

mio

.com

Sourc

e:

ww

w.c

hile

sust

enta

ble

.net

Product 2015 2016 2017 2018

Concentrate 4,431 4,653 5,369 5,987

Cathodes 2,018 1,998 1,904 1,812

Total 6,449 6,651 7,273 7,799

Projection of copper production, thousand of tons

Mining as a process of erosion


Tailing piplines, tailing ponds…

Mining duct

Sourc

e:

ww

w. dandili

on.c

l

Year 2012 2013 2014 2015 2016 2017 2018 2019 2020

Tailings 228,1 347,4 361,3 382,8 401,9 463,8 517,2 565,7 591,9

Projection in the generation of tailings (million tons)


Tailing piplines, tailing ponds…

Wear by erosion-corrosión in pump casings and impellers

Google Earh, June 2017


The erosion-corrosion synergy

metal

O2OH-

Fe2+

FeOH-

oEEC KK oCK ECK


oEEC KK oCK CE KK

metal

passive layer

O2OH-

Fe2+

FeOH-

Fe2O3/Fe3O4



)( CKIncrease of corrosion due to erosion



)( EKIncrease of erosion due to corrosion



CORROSIONCORROSION

INCREASED BY EROSION

EROSIONEROSION

INCREASED BY CORROSION

E-C TOTAL

LABORATORY(simple)

–Electrochemical testing

–Weight loss/gainin electrolyte

alone

–Additional current due to erosion

–Wear test under cathodic

polarization

–Wear test under anodic polarization

–Difference between other tests

–N/A

LABORATORY (physical simulation)

–N/A-–Additional current

due to erosion


polarization

- wear test under anodic polarization

- difference between total

weight-loss and data for corrosion, wear and wear-

enhanced corrosion

–Total weight loss/gain

MODELING(computational)

–Multiphysics modeling


–CFD–Multiphysics

modeling (not yet)–Multiphysics

modeling (not yet)

IN FIELD N/A N/A N/A N/A–Total weight

loss/gain

Methodology of E-C study


“In field” Spillage of concentrate slurry Los Andes, Chile (Feb 2016)

So

urc

e: w

ww

.lat

erce

ra.c

om


CORROSIONCORROSION


EROSIONEROSION


E-C TOTAL

LABORATORY(simple)



alone



polarization



–N/A



due to erosion


polarization




enhanced corrosion







modeling (not yet)


loss/gain



Experimental methods

Wood & Jones Wear 255 (2003) 206–218

Physical simulation

G.A. Zhang et al. Corr Sci 77 (2013) 334–341S-H. Wang et al., J.Bio.Tribo.Corros (2015) 1:9


Experimental methodsPhysical simulation

S.S. Rajahram et al., Tribol. Int 44 (2011) 232–240

C.I.Walker, P.Robbie, Wear 302(2013)1026–1034

M.M. Stack, et.al., Wear 261 (2006) 1181–1190


CORROSIONCORROSION


EROSIONEROSION


E-C TOTAL

LABORATORY(simple)



alone



polarization



–N/A



due to erosion


polarization




enhanced corrosion







modeling (not yet)


loss/gain



Modeling the E-C synergy

“Predictive” “modeling”J Fail. Anal. and Preven. (2016) 16:1071–1081

Interaction Power Model (IPM)Interaction Exponential Model (IEM)Interaction Second-Order Polynomial Model (ISM)


Modeling the E-C synergy

Semi-empiric model

sfimpmpef EEEEECCCCK EC

Rajahram et al., Wear 267 (2009)1883-1893Harvey et al, Tribol 1 (2007) 33

• Erodent damages passive layer activating corrosion• Erodent damages passive layer locally initiating pitting• Erodent deforms the surface increasing surface area and thus corrosion rate• Erosion enhances mass transfer facilitating electrochemical corrosion

• Galvanic corrosion between phases accelerates wear • Corrosion modifies mechanical properties affecting erosion• Corrosion at grain boundaries accelerated extraction of particles• Corrosion weakens the debris conveyed by erosion • Formation of passive layer accelerates wear loss


Modeling E-C in real geometriesTwo phase turbulent flow




Agenda


Case study: API 5L X65Experimental

SEM images of (a) quartz, (b) alumina and (c) SCT

a b c

Erodent Density [g/cm3] Circularity D50 (µm) D84 (µm)

SCT 2.77 ± 0.02 0.399 ± 0.04 44 152

Characteristics of the SCT erodent



Test material

Sample

Pot with baffles


Rotating cylinder electrode(basic enssembly)

Motor0-24,000 rpm

Frecuencyinverter

Acrylic pot(300 mL max.)

Shaft coverwith Teflon

Rotating cylinder electrode(with control of parameters)

pH-meter

Hot plate

Copper coil

O2 and N2

hoses

O2 probe

Metallicsamples

Temperatureprobes




FactorsLow level

Central High level Units Answer

Velocity 3 5 7 m/s

Weight loss (mg)

Concentration 45 55 65 % wt

pH 5 8 11 -

Temperature 25 35 45 °C

Content of oxygen 0 5 10 ppm

Content of copper ion

0 250 500 ppm

Material : API X65 (C max. 0.12%, Si max. 0.45%, Mn max. 1.6%, P0.025%, S max. 0.015%, and Fe the balance).

Liquid : Sodium sulfate 0.1 M (14000 ppm). Concentration of Cu2+ obtained byaddition of copper sulfate (CuSO4).

Time: Each test is run for 75 min to generate measurable weight loss.


DOE: Factorial design 26-1 (middle fraction) with central points

A total of 35 experiments were conducted to evaluate the damage for erosion-corrosion.

Run Velocity Tailing conc Temperature pH Cu2+ conc O2 conc

1 3 65 25 11 0 0

2 3 65 45 5 500 10

3 3 45 25 11 500 10

4 5 55 35 8 250 5

.. .. .. .. .. .. ..

35 7 45 45 11 0 10



Factor NameA VelocityB Tailing conc.C TemperatureD pHE Cu2+ conc.F O2 conc.

Type of effectNot significantSignificant

Normal graph of standardized effects (Wear (mg/cm2); = 0.05)

Significant effect

Velocity Oxygen Conc. Interaction Velocity-Oxygen

conc

The change in the value of the response by factor is not

random!!

Case study: API 5L X65Preliminary results

Standardized effect


O2

co

nc

en

tra

tio

n(p

pm

)

Velocity (m/s)

Contour graph of interaction between velocity and oxygen concentration



SEM on the effect of velocity for test at 45%wt in tailing concentration, 25°C, pH 11, 0 ppmin Cu2+ ions and 10 ppm of O2

3 m/s 7 m/s

10

00

×5

00

0 ×

•

•




SEM on the effect of oxygen concentration for test at 7 m/s, 45 wt% in tailing concentration, 25°C, pH 11 and 0 ppm in Cu2+ ions

0 ppm 10 ppm

BSE

50

00

×1

00

0 ×



SEM on the effect of oxygen concentration for test at 7 m/s, 45 wt% in tailing concentration, 25°C, pH 11 and 0 ppm in Cu2+ ions

0 ppm 10 ppm

Element Reference 0 ppm 10 ppm

Fe 91.99 84.27 77.28

C 4.21 3.58 6.06

O 3.8 9.52 14.37

Si - 1.8 1.47

Al - 0.83 0.83

Elemental composition ( wt%)

BSE

50

00

×




Agenda


Case study: API 5L X65

Mechanism

tested

Sample

code

Copper ion

concentrationConditions

EC

EC-0

EC-250

EC-500

0 ppm

250 ppm

500 ppm

SCT 55%wt. in 0.1 M Na2SO4

5 m/s

pH 5

E

E-0

E-250

E-500

0 ppm

250 ppm

500 ppm

SCT 55%wt. in 0.1 Na2SO4 M

5 m/s

pH 5

CP. -0.9 V

C

C-0

C-250

C-500

0 ppm

250 ppm

500 ppm

Only 0.1 Na2SO4

5 m/s

pH 5

Experimental conditions



Reference EC-0

EC-250 EC-500

SEM image of EC samples


Case study: API 5L X65 SEM image of EC samples


Case study: API 5L X65 SEM image of E-samples

E-0

Flow

direction

E-250

Flow

direction

E-500

Flow

direction

Reference



SampleEcorr (V vs

Ag/AgCl)icorr(A/cm2)

C-0 -0.460 0.00134

C-250 -0.521 0.00312

C-500 -0.564 0.00505

Electrochemical evaluation of loss by corrosion


Case study: API 5L X65 The weight loss synergy

Cu2+

metal

cathode

anodeē

Fe2+

FeOH-

Fe2O3/Fe3O4

Fe2+/ Fe3+

Cu0

slurry

Aguirre & Walczak, Tribol Int 2017



Conclusions

1. The statistical analysis allows concluding that the significantfactors in determining the total weight loss are velocity, contentof O2 and the interaction between them. This finding could beuseful for future predictive modeling of erosion–corrosionallowing simplification of the model.

2. Although the total E-C weight loss is not necessarily affectedby a particular factor, the relative contributions of corrosion (C),erosion (E), and synergy (S) might be affected by individualfactor as shown on the example of Cu2+ content.


Acknowledgment

FONDECYT No 1141107 (CONICYT) CONICYT Scholarship No 21150171 Undergraduate student: Nicolas Molina

Los Pelambres (Felipe Muñizaga) Migrin (Felipe Larrea) Minera Valle Central S.A. (Gonzalo Reyes)

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