ASTM Designation: B 545

Electrodeposited Tin Coating

Class Minimum Thickness Typical Applications
A 2.5 µm (100 µin) Mild service conditions, particularly where the significant surface is shielded from the atmosphere (as in electronic connector housings.)
B 5 µm (200 µin) Mild service conditions with less sever requirements than Class C.
C 8 µm (320 µin)10 µm (400 µin) for steel substrates Moderate exposure conditions, usually indoors, but more severe than Class B
D 15 µm (600 µin)20 µm (800 µin) for steel substrates Severe service, including exposure to dampness and mild corrosion from moderate industrial environments.
E 30 µm (0.0012 in) Very severe service conditions, including elevated temperatures, where underlying metal diffusion and intermetallic formation processes are accelerated.
F 1.5 µm (60 µin.) Similar to Class A, but for shorter-term contact applications and short shelf-life requirements, subject to purchaser approval.

Surface Appearance Type (Electroplating Process)

Matte Tin Electrodeposits – Coating with a matte appearance are obtained from tin plating baths (stannate, sulfate, methylsulfonate, and fluoborate) used without the addition of brightening agents.

Bright Tin Electrodeposits – Bright coatings are obtained when proprietary brightening agents are used in specific bright tin plating baths.

Flow-Brightened Electrodeposits – Flow –brightened coatings are obtained by heating the matte coating above the melting point of tin for a few seconds, followed by quenching.