Our silver anodes in our cyanide silver bath have turned black. What is causing this problem?
The most likely reason for this is low-cyanide concentration in the silver plating bath. Check your cyanide concentration and bring it within the range specified by the vendor of your silver plating bath chemistry. Another cause, which is not anywhere as common, is gold contamination in the silver anode. This blackening usually occurs when the gold concentration in the anode is greater than 60-80 ppm.