Standard Specification for Electrodeposited Coatings of Tin	ASTM B-545
Class	Minimum Thickness	Application
A	2.5 um (100 u")	Mild service conditions.
B	5.0 um (200 u")	Mild service conditions. Facilitates soldering.
C	8.0 um (320 u") 10 um for Steel substrates	Moderate , usually indoor, exposure conditions. Retention of solderability.
D	15 um ( 600 u") 20 um for Steel substrates	Severe service. Exposure to dampness and mild corrosion from moderate environments.
E	30 um ( 1200 u")	Very severe service conditions including elevated temperatures where metal diffusion process is accelerated.
F	1.5 um ( 60 u")	Similar to Class A. Short term contact applications