Mils Per Year (MPY) Corrosion Rate

Converts coupon weight loss into a corrosion rate expressed as thickness lost per year. One mil is one one-thousandth of an inch. Recommended coupon exposure is about 90 days to allow passivation and give a representative long-term sample.

$$\text{MPY}=\frac{534\times W}{D\times A\times T}$$

Variables

Symbol	Meaning	Unit
534	Unit conversion factor	dimensionless
W	Weight loss	mg
D	Density of the metal (carbon steel is 7.87)	g/cm^3
A	Surface area of the coupon	in^2
T	Time exposed	hr

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Part of The Blueprint of Water