The following charts provide a simple way to convert data between the most common corrosion units in usage, i.e. corrosioncurrent (mA cm-2) , mass loss (g m-2 day-1) and penetration rates (mm y-1 or mpy) for all metals or for steel
mA cm-2 | mm year-1 | mpy | g m-2 day-1 | |
mA cm-2 | 1 | 3.28 M/nd | 129 M/nd | 8.95 M/n |
mm year-1 | 0.306 nd/M | 1 | 39.4 | 2.74 d |
mpy | 0.00777 nd/M | 0.0254 | 1 | 0.0694 d |
g m-2 day-1 | 0.112 n/M | 0.365 /d | 14.4 /d | 1 |
where:
mpy = milli-inch per year
n = number of electrons freed by the corrosion reaction
M = atomic mass
d = density
For example, if the metal is steel or iron (Fe), n =2, M = 55.85 g and d = 7.88 g cm-3 and the Table of conversion becomes:
mA cm-2 | mm year-1 | mpy | g m-2 day-1 | |
mA cm-2 | 1 | 11.6 | 456 | 249 |
mm year-1 | 0.0863 | 1 | 39.4 | 21.6 |
mpy | 0.00219 | 0.0254 | 1 | 0.547 |
g m-2 day-1 | 0.00401 | 0.0463 | 1.83 | 1 |