# Ch-17, Corrosion & Oxidation¶

## example-17.1 page no-511¶

In [2]:
from __future__ import division
#given
#density of nickel and nickel oxide (NiO)
rhom=8900  #kg/m**3
rhoc=7080  #kg/m**3
#molecular weight of nickel and nickel oxide
Mm=58.51
Mc=74.71
#molar volumes are
Vm=Mm/rhom  #m**3/mol
Vc=Mc/rhoc  #m**3/mol
if Vc>Vm:
print " it is clear that Vc>Vm, so a protective film will form over nickel"
else :
print " it is clear that Vc<Vm, so a protective film will not form over nickel"

 it is clear that Vc>Vm, so a protective film will form over nickel


## example-17.2 page no-513¶

In [7]:
from math import sqrt
#given
#oxidation loss on the copper surface is 0.1 mm in 25 hours
t1=25  #hours
x1=0.1  #mm
#to find the loss in 300 hours
t2=300  #hours
# as we know that oxidation loss is given by
#x**2=Cp*t
#for t1 and t2 we have following equations
#x1**2=Cp*t1  -------(1)
#x2**2=Cp*t2   -----------(2)
#dividing equation 1 by 2
#we get
x2=x1*sqrt(t2/t1)   #mm
print "Loss in 300 hours is %0.3f mm"%(x2)

Loss in 300 hours is 0.346 mm


## example-17.3 page no-515¶

In [4]:
#given
#atomic weight  and density of magnesium
MMg=24.3  #gm
rhoMg=1.740  #g/cm**3
#molecular weight and density of MgO
MMgO=40.3  #gm
rhoMgO=3.650  #g/cm**3
#volume of Mg and Mgo
VMg=MMg/rhoMg  #cm**3
VMgO=MMgO/rhoMgO  #cm**3
#we know that pilling-bedworth ratio is given by
PBR=VMgO/VMg
if PBR<1:
print "Since PBR is less than 1 so the film formed is not protective "
else:
print "Since PBR is greater than 1 so the film formed is protective "

Since PBR is less than 1 so the film formed is not protective


## example-17.4 page no-526¶

In [8]:
#given
#one mole of magnesium weighs
MMg=0.0243  #Kg
#current density
I=20*10**-3   #A/m**2
#design life of 15 years
t=15*365*24*3600  #sec

the amount of magnesiun meeded is 1.191 kg/m**2