Decreased Efficiency of Alkaline Plating Baths due to Carbonates

Alkaline plating baths (zinc, zinc-nickel, copper, cadmium, etc.) tend to slow down as they age and one of the main culprits is the formation of carbonates. There are two main mechanisms that introduce carbonates into the plating bath. The first occurs when carbon dioxide in the atmosphere reacts with water to form carbonic acid. The carbonic acid in turn reacts with the alkaline plating solution to form carbonates. The second mechanism contributing to the buildup of carbonates, is the formation of oxygen at the anode interface. This oxygen can react with the organic compounds that are in solution to form carbonates.

Carbonates are in all alkaline plating baths and do not cause a problem in the 6-10 opg range. Once carbonate levels climb to 12 opg and above there are several detrimental effects that begin to occur. These issues include less efficient plating (slower plating speed), reduced ability of the bath to throw (plate in LCD areas), increased brighteners required, burned deposits in HCD areas and plating roughness. All result in increased production costs!

There are only three methods of removing carbonates from plating solution. The first is to freeze out the carbonates. Customers generally fill totes with the plating solution and place outside during the winter. Between 35- and 40-degrees F, the carbonates will freeze out of solution and form a solid build up within the totes which is subsequently scraped off and hauled away. The remaining solution is pumped back into the tank and brought back to proper operating parameters. The second is to simply decant the plating bath by cutting and adding back the required chemistry to get back to operating levels. Either of the first two methods consume significant “good” operating solution and add subsequent costs through chemistry losses as well as labor. The last method is through specially designed carbonate removal systems. This is where BroCo Products comes into play.

There are several systems on the market to help solve this issue. A specific volume of plating solution is taken by these systems. The solutions temperature is dropped to freeze out carbonates in batches and the remaining solution is returned to the plating tank. The advantages of these systems are increased productivity through more efficient plating chemistry and uninterrupted operation during carbonate removal periods. The removal can be consistently performed to maintain optimal plating efficiency for longer periods of time at lower costs.