In a paper, I saw Pr = (1.116x10^7 x WL)/(AxT)
Pr = corrosion rate (um/year)
WL= weight loss (g)
A = Surface area (cm^2)
T = Time elapsed (Hours)
Can someone help me to derive this equation?
Thank you.
Refer this link:http://link.springer.com/chapter/10.1007/978-90-481-3477-9_5#page-1
Refer this link:
corrosion is stipulated in weight loss (mass dissolved) unit area/per time unit.
or depth lost (dissolved) per time unit.
in mass / depth it is essentially the density.
so why not apply simple arithmatics to help yourself
In order to help You understand from where 1.116x10^7 comes from, I need to know what metal is concerned in the paper. The Faraday law uses the number of electrons produced by the oxydation of the metal, could be 1 or 2 etc...and the atomic mass of the element....need to know the element.
Calculation of Corrosion Rate from the Corrosion Current
According to Faraday’s Law:
W = QM/nF (equ.1)
Where
Q = coulombs
n = number of electrons involved in the electrochemical
reaction
F = Faraday constant, 96,487 coulombs
W = weight of the electroactive species, gram
M = molecular weight
Since equivalent weight EW= M/n
and since Q = it from Faraday’s Law
where
i is the current, amp
t is the exposure time, sec.
so, W/t is the corrosion rate (C.R.) in grams/second.
It is convenient and traditional to express corrosion rate as milli-inches per year (mpy). These units provide an indication of penetration.
Dividing equation (1) by the electrode area and the density of the metal sample gives:
C.R. (cm/sec) = i (E.W.)/dFA
Convert seconds to years and centimeters to milli-inches.
Convert the Faraday (amp-sec/eq) to microamps.
Express the terms i/A as current density. Combining all
the constants gives:
Corrosion Rate (mpy) = [ 0.13 ICORR (E.W.)]/d (Eq. 2)
ICORR = corrosion current density, μA/cm2
E.W. = equivalent weight of corroding species, g
d = density of corroding species, g/cm3
Equation (2) is used to calculate the corrosion rate
directly from ICORR.
Conversion of (Eq.2) from mpy to micrometer per year (um per y), Equ.2 becomes;
Corrosion Rate (um py) = [3.302 ICORR(EW)]/d
Then try to mathematically manipulate the above equation(Equ.2) to:
corrosion Rate = (1.116x10^7 x WL)/(AxT)
If you divide the weight corrosion rate in the unit [g/(cm2 h)] by the density of the metal, you will receive the linear corrosion rate in the unit [mm/year]. Remember that you have to convert hours to the year: 8760 hours per year.
- Badges
- Science topic
- Similar topics
- Engineering
- Materials Engineering