Silver Plate Hardness

[metrat]

I have many components that get silver plated, per either AMS-2410 or AMS-2412. I have tried to do some microhardness testing to determine the hardness of the plating, but get values that are suprisingly low.

Anyone have a rough idea of how hard I should expect the plating to be?? Any info. would be appreciated. Thanks.

 

[kenvlach]

What values did you get?
Was this dull/matte, semi-bright or bright plating? The type of plating solution (and especially, the brightener additive) have a major effect on the hardness.

One reference says silver plate per QQ-S-365D hardness ranges from about 90 to 135 Brinnell. [I don’t have the AMS specs].

The Metal Finishing 2003 Guidebook and Directory (print version) chapter on silver plating says typical cyanide-type plating solutions, absent any brighteners, produce matte finish silver of hardness < 100 Knoop. The use of brighteners increases the hardness to between 100 and 200 Knoop. The use of antimony and selenium will produce higher hardness than organic brighteners, although the latter generally have better electrical conductivity.

There are also some newer, non-cyanide plating solutions, but according to the Guidebook, brighteners have not yet been developed. I would guess that these produce pretty soft coatings.

If you cannot get information from your plater or their chemical supplier about the plating solution and expected hardness, try Technic at

http://www.technic.com/chm/chem.htm