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Corrosion Rate Conversion

The following charts provide a simple way to convert data between the most common corrosion units in usage, i.e. corrosion current (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

Note: you should read the Table from left to right, i.e.:

1 mA cm-2 = (3.28 M/nd) mm y-1 = (129 M/nd) mpy = (8.95 M/n) g m-2 day-1

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

Note: you should read the Table from left to right, i.e.:

1 mA cm-2 = 11.6 mm y-1 = 456 mpy = 249 g m-2 day-1