Lumpy Silver

I have recently been assigned over sight of our plating division and have a problem that is driving us nuts, we are plating reel to reel copper wire at .040 dia. with approximatly 300 microinches of silver plating. it is a standard cyanide bath that is new. Lumps and a high carbonate level caused us to change out the old. The contact wheels are 316 L and seem to have a new propensity for self plating small grains that in turn stick to the wire after a short time of running. Immediate cleaning of the contacts and we are back running OK for about 25 pounds when the wire begins the same lumpy feel. All bath parameters appear to be in line, any thoughts as to why a sudden contact wheel plateability would be appreciated.

Hey Randy,

The contact wheels may have lost their passivation. Oxidation/Reduction reactions in the pores or on the surface of the steel may be to blame. Repassivation or better yet, new contact wheels should help. Air blow-downs and/or an intermittent spray rinse can be used to keep solution off of the contact wheels.

Hope this helps,