Question

Which of the following units are used in terms of penetration of pits on a metal?

(a) Milligram sq. decimeter per day (MDD)

(b) Mils per year (MPY)

(c) Both MDD and MPY

(d) Neither MDD nor MPY

This question was addressed to me in homework.

The query is from Testing in division Corrosion Testing of Corrosion Engineering

Answer 1

Right answer is (b) Mils per year (MPY)

To explain I would say: Mils per year is commonly used corrosion rate expression as it measures corrosion rate in terms of depth of penetration of pit. Whereas milligram sq. decimeter per day (MDD) measures the corrosion rate in terms of weight loss of metal.