Development of Corrosion andHydrogen Permeation Resistant

Nanostructured Composites

Branko N. PopovBranko N. PopovCenter for Electrochemical EngineeringCenter for Electrochemical EngineeringDepartment of Chemical EngineeringDepartment of Chemical Engineering

University of South Carolina, Columbia SC 29208University of South Carolina, Columbia SC 29208

ØDevelopment of novelprocesses and treatmentsfor synthesis ofnanostructured materials.ØDevelopment of

mathematical models whichhelp to engineer andoptimize the materialssurface and bulk properties.ØDevelopment of novel

hybrid nanostructuredmaterials with superiorcorrosion properties.

Presentation Outline

Hydrogen Induced Cracking

Hydrogen is produced duringØCorrosionØElectroplatingØCharging secondary batteriesØCathodic protectionHydrogen in alloy can cause catastrophic failures via:ØHydrogen embrittlementØBlisteringØHydrogen induced cracking

Mitigation of Hydrogen Permeation

Current methods for decreasing hydrogen permeationlike temperature treatments and laser modification donot decrease the hydrogen penetration rate to the safelevel

Our approachØInhibit the hydrogen discharge reaction rate

ØIncrease the recombination reaction rate

ØInhibit hydrogen absorption into the metal

ØForm a physical barrier to hydrogen diffusion

Development of Novel Treatments for Synthesis ofNanostructured Materials with Superior Corrosion Properties

Superior corrosionproperties

Synthesis of Nanostructured Materials byElectrochemical Processes

UnderpotentialDeposition (UPD)of monolayers ofZn, Ni, Bi onto

hard alloys

Novel autocatalyticreduction process for

deposition ofamorphous Zn-Ni-P

alloys

DC and Galvanostatic pulsetreatments for deposition of

ternary and quarternarycomposites based on Zn, Ni,

P and SiO2

Superior corrosion and hydrogenpermeation inhibition properties

Superior mechanical properties(low rates of hydrogen

permeation and corrosion)

DC and Pulse Deposition of NanostructuredMultilayers

ØThe particle nucleation rate andthe grain size is controlled by thepeak cathodic potential, the pulseperiod and the relaxation periodand the duty cycle.ØThin films and nanostructured

deposits have been deposited byoptimizing the duty cycle and theconcentration of leveling agents.ØThe film grain size is

proportional to the crystal growthrate and inversely proportional tothe nucleation rate.ØPulse deposition increases the

nucleation rate, decreases thecrystal growth rate.

Multiple Layers of Zn-Ni

Nanostructured Zn-Ni-P

1 µm

1 µm

Underpotential Deposition of Zn

Underpotential Deposition of NanostructuredMonatomic Layers of Zn, Pb and Bi

Ø UPD occurs with a formation of monatomic layers atpotentials more noble than the reversible Nernstpotential

Ø UPD has been optimized for Zn, Pb and Bi by using thework functions of these metals and the work function ofthe substrate

Ø The Underpotential shift (E) when the monatomiclayers are formed is determined by the difference inwork functions in electron volts of both metals

Ø UPD formed monatomic layers pf Pb, Bi and Zn onsteel surface inhibit corrosion due to lowering of thebinding energy of the hydrogen adatoms on Zn,Pb andBi adsorbates.

Experimental

Ø HY-130 Steel (0.4 cm2) was used as the substrate

Ø Devanathan-Stachurski permeation technique wasused to study hydrogen inhibition

Ø Cathodic solution during permeation was 1M Na2SO4

+ 0.4 M NaCl + 1M H3BO3

Ø For underpotential deposition of Zinc, 2X10-3 M Zn2+

ions were added to the catholyte

Ø Anodic solution during permeation was 0.2M NaOH

Ø Anodic side of the membrane was coated with 0.15-0.2 µm thin layer of Pd

Devanathan-Stachurski Technique

ØThe hydrogen permeation current wasmeasured continuously as a function of time.ØThe permeation current was measured by

setting the potential on the anodic side of themembrane at -0.3 V vs. Hg/HgO.ØCathodic side of the membrane was polarized

potentiostatically creating conditions forUnderpotential deposition of Zn or Pb.ØZero concentration of absorbed hydrogen on

the anodic side of the membrane wasmaintained by instantaneous oxidation ofdiffusing H.

Hydrogen Permeation Cell

CVs obtained on HY 130 with electrolytecontaining different Zn concentrations

Hydrogen permeation curves through aHY 130 steel

Hydrogen permeation curves through a HY130 steel in presence of zinc ions

Dependence of hydrogen entry efficiency as afunction of applied cathodic overpotential

Conclusions

Ø Underpotential deposition of Zinc inhibits the discharge ofhydrogen on HY-130 steel.

Ø In the presence of a monolayer coverage of Zn, hydrogenevolution currents were reduced by 58%.

Ø Hydrogen atom direct entry mechanism has been usedalong with a mass transfer correction term to interpret thepermeation data.

Ø In the presence of Zn, hydrogen entry efficiency in thealloy and hydrogen entry rate constant were reduced by afactor of three and by 74% respectively.

G. Zheng, B. N. Popov, and R. E. White, "Use of Underpotential Deposition of Zinc to MitigateHydrogen Absorption into Monel-K500," J. Electrochem. Soc., 141, 1220-1224 (1994).

Summary of Experimental Results

Alloy Additive Decreasingof ic

Decreasingof j∞

Relation between j∞

and ic

Model

Zn2+ 46% 51% - -Pb2+ 44% 71% j∞ α ri

Conventional ModelAISI - 4340

Bi3+ 85% 65% - -Zn2+ 58% 90% j∞ α ic Direct EntryHY-130Tl1+ 83% Increasing

74%j∞ α ri and j∞ α ir conventional

model

Zn2+ 68% 40% - -Inconel-718Pb2+ 67% 70% - -Bi3+ 60% 76% - -

Monel-K500 Zn2+ 60% 60% - -Pd - - - j∞ α ic Direct Entry

Deposition of Multiple NanostructuredZn Layers

Objectives

ØTo investigate the effect of bulk deposition ofzinc layer on hydrogen permeation through aniron membraneØTo study the effect of thickness of the Zn-layers

on hydrogen permeation through themembrane.ØTo estimate the parameters governing the

hydrogen permeation through the ironmembrane using a conventional permeationmodel.

Experimental

Ø The zinc layers are deposited using a solutionconsisting of 1.0 M H3BO3 + 1M Na2SO4+ Zn SO4

Ø Nanostructured Zn layers were depositedgalvanostatically at 0.8 mA for 2-5, 10, 20 or 40 s.

Ø Assuming 100% current efficiency this wouldcorrespond to a Zn layer of 100nm thickness for each40 s of plating.

Ø Measurements of the cathodic current and permeationcurrent at different applied cathodic potentials, Ec weremade of the bare iron substrate and subsequently aftereach layer was plated.

Multiple Electroplated Zinc Layers forHydrogen Permeation Inhibition

0 50 100 150 200

Plating time (s)

10

20

30

40

50

60

70

j ∞ (µ

A/c

m2 )

i c (µA

/cm

2)

0

800

1600

2400

3200

4000

Multiple Electroplated Nanostructured ZincLayers for Hydrogen Permeation Inhibition

8.346.251.01160

6.206.991.021208.048.701.04100

4.629.831.24804.6911.41.2570

4.9414.71.28605.0320.61.4750

5.2228.21.55407.5641.71.7830

9.9762.01.992010.872.16.2510

69.880.6139Bare Iron (s)k3(109mol/cm2s)k”(106mol/cm3)io=io

’(1010A/cm2)Layer

Decrease of ic and j∝ with NanostructuredZn layers on Carbon Steel

20 s 40 s 60 s 80 s 100 s 120 s 160 s

ic 86 90 92 93 92 93 93

j∞ 61 82 91 93 95 96 96

Ø Hydrogen evolution and Permeationdecreased with each successivenanostructured zinc layers to 93% and 96%respectively as compared with bare iron

Ø Decrease in the permeation rate of hydrogenthrough the iron membrane was due tov Decrease of hydrogen discharge ratev Suppression of hydrogen absorption and

adsorption on deposited zinc layers

Conclusions

Deposition of Ternary Zn-Ni-X (X= P,SiO2,) Alloys

NanostructuredZn-Ni multilayers

Nanostructured Zn-Ni-Cd

1 µm1 µm

Synthesis of Nanostructured Layers of Zn-Ni-Cd

ØDeveloped a newelectrodeposition technique thatcan control the Zn-Ni ratio andthereby the barrier properties ofthe nano deposits.ØThe ability to control the Zn-Ni ratio helps in engineeringcoatings that are galvanicallycompatible with the substratesØ Zn-Ni-Cd coatings can beregarded as replacements forcadmium plating.

0.0 0.5 1.0 1.5 2.0 2.5 3.0Time (hour)

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

Pote

ntia

l (V

vs.

SCE

)

Zn-Ni-Cd(3 g/l CdSO 4)

Zn-Ni

Zn

Nickel

Cadmium

Steel

Nanostructured AlkalineZn-Ni-Cd (47/28/25%)

Objective

ØTo develop Zn-Ni-X ternary alloy coatingsØTo study the corrosion and hydrogen

permeation behavior of the developed coatingsusing electrochemical techniquesØCompare the results to that of cadmium

Our Approach

ØControl Zn-Ni ratio; increase Ni contentvincreases barrier properties

ØDecrease the Corrosion potentialvreduces the dissolution rate

ØModify hydrogen evolution, recombinationand absorption kineticsvinhibits hydrogen permeation

Objectives for Zn-Ni-X (X=P, SiO2) Composites

ØTo electrodeposit a Zn-Ni-X alloy thatvProvides Sacrificial Protection to ironvHas low dissolution rate in corrosive media

Ø To study the hydrogen permeation inhibitioncharacteristics of the new Zn-Ni-X alloy byvDetermining various kinetic properties

characterizing hydrogen permeation inhibitionunder corroding conditionsvComparing the hydrogen permeation inhibition

characteristics with Zn-Ni

A. Krishniyer, M. Ramasubramanian, B. N. Popov and R. E. White, “Electrodeposition &Characterization of a Corrosion Resistant Zinc-Nickel-Phosphorous Alloy,” Journal of the AmericanElectroplaters and Surface Finishing Society, January (1999) 99-103.

ExperimentalØ Zn-Ni alloy deposited galvanostatically fromv0.5M NiSO4 + 0.2M ZnSO4 + 0.5M Na2SO4; pH=3.0

Ø Zn-Ni-P alloy deposited galvanostatically fromvAbove Solution + 100 gpl NaH2PO2; pH=3.0

Ø SiO2 was deposited on top of Zn-Ni alloy by usingtechnology developed at USC for Elisha technologies

Ø Fe foil, 99.5% pure, 0.1 mm thick, 4 cm2 area was used assubstrate

Ø Composition analysis was done using EDAXØ Linear polarization technique was used to find RP

Ø Devanathan-Stachurski permeation technique was usedto study hydrogen inhibition

Ø Cathodic solution during permeation was 1M Na2SO4 +1M H3BO3 ; at various pH values

Ø Anodic solution during permeation was 0.2 M NaOH

Surface Morphologies of Zn-Ni and Zn-Ni-X alloyelectrodeposited galvanostatically at 5 mA/cm2

Zn-Ni-PZn-Ni Zn-Ni-SiO2

Ni- 9.5%Zn-90.5%

Ni- 4.27%Zn- 67.03%SiO2-28.70%

Ni- 9.0%Zn-90.0%P - 1.0%

Linear polarization studies on different deposits

-50 -30 -10 10 30 50

Current (µA/cm2)

-5

-3

-1

1

3

5

η (m

V v

s. S

CE

)

Zn-Ni-SiO2

Rp = 32000 Ω

Zn-Ni

Rp = 300 Ω

Zn-Ni-P

Rp = 600 Ω

Zinc

Rp = 167 Ω

Corrosion rates for different nanosize coatings

0

5

10

15

20

25

30

35

40

45

50

Corrosionrate inmpy

Zn-48.92

Cd-21.31Zn-Ni-22.12

Zn-Ni-P-10.7 Zn-Ni-

SiO2-0.3

Current WorkElectroless Deposition of Zn-Ni-P

Electroless Ni-P Electroless Zn-Ni-P

SEM Analysis of Electroless Zn-Ni-P

Ni- 97.9%P - 2.1%

Ni- 71.3%Zn-13.8%P -14.9%

Linear polarization studies on different deposits

-30 -20 -10 0 10 20 30

Current (µA/cm2)

-10

-5

0

5

10O

verp

oten

tial η

( mV

vs

SCE

)

Electroless Zn-Ni-P

Rp=1663 Ω,

OCV=-0.641 V

Electrodeposited Zn-Ni ,

Rp=167 Ω, OCV=-1.083 V

Electroless Ni-P

Rp=3592 Ω,

OCV=-0.399 V

Zn, Rp=300 Ω,

OCV=-1.120 V

Ø Deposit nanostructured Zn-Ni-Cd, Zn-Ni-P, Cd on AerMet 100samples

Ø Three different depositthickness of 2, 4, and 6 µm with%yield strengths of 50 and 75.

Ø Stress Corrosion Evaluation ofCoated and Bare AerMet 100specimens

Ø Polarization studies to comparethe corrosion rates of each of thecoatings with that of bareAerMet 100 alloy.

Current work for NASA

Development of Corrosion model

Hydrogen Permeation Model underCorroding Conditions

Ø Hydrogen evolution is the onlycathodic reaction

Ø Hydrogen permeation occursonly by diffusion of absorbedhydrogen

Ø The membrane is homogenouswith no hydrogen trappingsites

Ø The process is steady state

M. Ramasubramanian, B. N. Popov and R. E. White, "Characterization of Hydrogen Permeationthrough Zinc-Nickel Alloys under Corroding Conditions," J. Electrochem. Soc., 145, 1907 (1998).

Relationship between ln(iRelationship between ln(irr0.50.5/ j/ j∞∞) and j) and j

0.3 0.5 0.7 0.9 1.1

Jα, mA/cm2

3.0

3.5

4.0

4.5

ln((

I r)0.

5/J

α)

3 g/l CdSO4

1 g/l CdSO4

Corrosion Model

Nads

Nabs

NH

Ndes

Ndsb

CathodicSurface

x=0

AnodicSurface

x=L

NPerm(iCorr)

(irec)

(j∞)(j∞)

Discharge

Recombination

Absorption

adsk MHeHM →++ −+ 1

abs

k

kads MHMH3

4

⇔

MH e H MH 2k-

ads2 +→++ +

Development of Corrosion Model

)fexp()C-(1k zFi

N pH1

cads ηα−θ== +

)exp(qHC2k ηαθ fzF

ridesN −+==

NH = Nads - Ndes

NH = Nabs - Nrab

LC

D- N absH =

Parameter Estimation from Model

q

HaC

kk

j)fexp(i 2r

+=ηα

∞

pH1c CzFk )fexp(i +=ηα

∞−

+ =ηα jkk - zFk C)fexp(i

a

11

1pHc

NH = Nabs - Nrab absCkk 43 −= θ

azFkj∞=?

DL

k

kka

4

3

1+=

ic = ir + j∝MHads=MHabs;

Nabs = k3θNrab = k4(1-θ)Cabs

LC

D- N absH =

Plot of the Recombination function against theHydrogen ion concentration for Fe and Zn-Ni Alloy

-10 -9 -8 -7 -6 -5

log (CH+) (mol/cm 3)

-5

-4

-3

-2

-1

-0

1

log

(1/j ∞

i re(α

fη) ) Fe

Zn-Ni

Experimentally Determined Parameters for HydrogenPermeation Through Zn-Ni Nanolayers

Fe Zn-Ni

k1(mol/cm2s)

k2 (mol/cm2s)

ka (mol/cm2s)

p

q

1.0 × 10-12 1.5 × 10-12

1.8 × 10-13 3.9 × 10-12

2.85 × 10-9 9.09 × 10-11

-0.196 0.286

-0.476 0.227

θ 0.0125 0.075

Comparison of cathodic and permeation currentdensities for Zn-Ni-Cd, Zn-Ni and Steel

100 101 102 103 104

Ic and Jα (µA/cm2)

-0.8

-0.6

-0.4

-0.2

η (V

vs.

SC

E)

Jα, 3 g/l CdSO4

Jα, Zn-Ni

Ic, Steel

Jα, Steel

Ic, 3 g/l CdSO4

Ic, Zn-Ni

Experimentally Determined Parameters for HydrogenPermeation Through Nanostructured Layers of Zn-Ni-Cd

2.54x 10-10

1.78x 10-10

1.58x 10-15

k2, mol/cm2s

59.243.90.285ka mol/cm3

x10-8

0.212.616.98io, A/cm2

x10-4

Zn-Ni-Cd (5:2:3)Zn-Ni-Cd(16:3:1)Steel

Percentage Decrease in Permeation Current*of Different Nanostructure Coatings

* At over potential of 300 mV.

10.88

1.27

0.50

0.30

Coating Permeation current,µA/cm2 % Decrease

Steel

Zn-Ni

Zn-Ni-P

Zn-Ni –SiO2

-

88

95

97

Conclusions

Ø Developed a new electrodeposition technique that cancontrol the Zn-Ni ratio and thereby the barrierproperties of the nano deposits

Ø The ability to control the Zn-Ni ratio helps inengineering coatings that are galvanically compatiblewith the substrates

Ø Developed a mathematical model to evaluate thepermeation characteristics under corroding conditions

Ø Zn-Ni-SiO2 and Zn-Ni-P coatings have been developedthat are environmentally benign and can be regardedas replacements to Cd plating.

• Process optimization studies will be carried by scalingup the process.• Bench scale depositions• Require larger electrolytic cells

• Optimization of the novel Zn-Ni electroless depositionprocess to obtain corrosion and hydrogen permeationresistant deposits

• Development of Electroless Plating Techniques forobtaining Zn-Ni-P and Zn-Ni-SiO2 alloys.

• Hydrogen permeation characterization studies forelectroless plated alloys

Future Work