Scope:

ASTM A428 test technique establishes a standard for determining the mass of aluminum coatings applied to iron or steel items. Aluminum coatings on iron or steel objects produce a relatively inert barrier that protects the objects against corrosion. A thicker layer will provide more protection against mechanical damage that would otherwise cause the coating to crack.

Test Procedure:

In ASTM A428, the aluminum coating from the specimens is removed using a razor blade. Then, the specimens are cleaned by washing them in petroleum ether or another suitable solvent and then weighed. At about 195 °F (90 °C), the specimens are immersed in a NaOH solution. Then, at room temperature, each specimen is immersed in HCl (sp gr 1.18 to 1.19) for no more than 3 seconds after which the specimen is scrubbed with a sponge under running water, then reimmersed in the hot NaOH solution.

Specimen Size : 

For ASTM A428, the specimen is created to the measurements specified, with an area of 5.08 in².

Data:

The following formula is used in ASTM A428:

C= [(W₁-W₂)/W2]×T×K

where:

C – mass of the coating 

W₁– original weight

W₂ – weight of the stripped specimen

T – thickness 

K – constant

Conclusion:

The average coating mass over a particular area of aluminum coated steel or iron article is determined using ASTM A428.