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ASTM Designation: B 545

Electrodeposited Coatings of Tin

ClassMinimum ThicknessTypical 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 substratesSevere 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.

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