Chapter 17: Corrosion and Degradiation of Materials

Example 17.1 Page No 629

In [8]:
V_Cd=-0.403  #Half Cell Potential of Cd++|Cd
V_Ni=-0.250  #Half Cell Potential of Ni++|Ni

dV=V_Ni-V_Cd
C_Ni=10**-3
C_Cd=0.5
n=2          #Net electron exchange in Redox reaction
V=-dV-(0.0592*math.log10(C_Ni/C_Cd)/n)

print"Standard Cell potential is ",dV,"V"
print"Net EMF is ",round(V,3),"V"
if V<0:
    print"Ni is reduced & Cd is oxidised"
else:
    print"Cd is reduced & Ni is oxidised"

Standard Cell potential is  0.153 V
Net EMF is  -0.073 V
Ni is reduced & Cd is oxidised

Example 17.2 Page No 637

In [12]:
VZn_Zn2=-0.763
iZn=10**-7
beta_Zn=0.09
iH2=10**-10
VH_H2=0
beta_H2=-0.08

ic=10**((VH_H2-VZn_Zn2-(beta_H2*math.log10(iH2))+(beta_Zn*math.log10(iZn)))/(beta_Zn-beta_H2))
n=2              #Exchange of 2 electrons
F=96500          #Faradays constant
r=ic/(n*F)
Vc=VH_H2+(beta_H2*log10(ic/iH2))

print"i) Rate of oxiadation is",round(r,12),"mol/cm**2-s"
print"ii) Corrosion potential is",round(Vc,3),"V"

i) Rate of oxiadation is 6.18e-10 mol/cm**2-s
ii) Corrosion potential is -0.486 V
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