1. The problem statement, all variables and given/known data(adsbygoogle = window.adsbygoogle || []).push({});

Iron sample with dimensions 10mm x 20mm x 2mm is exposed to a corrosive environment (neglect thickness for surface area). Both sides of the sample are exposed to corrosive environment. Given http://i.imgur.com/tGRw4.jpg"

(a) Calculate corrosion rate mm/y

(b) Calculate corrosion rate if one of the sample surfaces is painted (not in contact with corrosive environment)

2. Relevant equations

M=56g,

t=3.1536e7 sec/yr

number of electrons taking part n=2

F=96500C

density=7.87g/cm3

A=10*20=200mm2

From Faraday's Law: W=MtI/nF (W=weight loss, I=current in this case corrosion current)

3. The attempt at a solution

(a) From Tafel Plot log(Icorr)=0.05mA/cm2 so Icorr=1.12e-3 A/cm2

I want to convert Icorr to just units of A, but since both surfaces are exposed should I multiply it by double the surface area?

i.e.: Icorr=1.12e-3*200mm2*2*(1cm/10mm)^2 = 4.48e-3 A

substituting in W=Mt*Icorr/nF = 40.99 g/yr

Corrosion Rate CR=W/density*Surface Area

Again I multiplied the Surface Area by 2 because both sides of the Iron sample is exposed

CR=(40.99g/yr)/[(7.87g/cm3)*(200mm2*2)*(1cm/10mm)^3)]=13.02mm/yr

(b) For only one side exposed:

I'm going to use half of Icorr since only 1 side is exposed so Icorr=2.24e-3 A

then W=20.49g/yr

Using only 200mm2 as the surface area

CR=(20.49g/yr)/[(7.87g/cm3)*(200mm2)*(1cm/10mm)^3)]=13.02mm/yr

I get the same corrosion rate...is this correct?!

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: How to calculate corrosion rate?

Can you offer guidance or do you also need help?

Draft saved
Draft deleted

**Physics Forums | Science Articles, Homework Help, Discussion**