By Doug Trageser
In our most recent series “Water and the Plating Process”, we focused on how water quality can affect the plating process starting with cleaners and rinses all the way to the final finish. As an experienced finisher knows, even with “clean” water ahead of the plating system, the plating baths need regular cleaning in order to maintain high-quality finishes and a steady state operation.
Filtration
Arguably, the most important detail to keeping a plating line clean is filtration. A lack of good filtration can lead to many issues, such as shelf roughness, pitting and blistering. If the economies of scale permit it, filtration in the cleaner baths, rinse tanks and acid activation bath is a good practice for limiting the contamination that reaches the plating baths. As an example, we recently recommended for a client to put carbon filtration in a rinse tank after nickel plating and prior to chrome. A couple of weeks before, they had a fire in the building and were dealing with debris falling into the tanks. The debris was leaving an oily residue on the nickel plated parts that showed up after chrome plating. The problem went away by using an in-tank filtration system with a carbon cartridge.
Filtration units come in many shapes and sizes. Experienced finishers have a comfort level with certain types of filtration systems, whether it’s a horizontal plate filter, bag filter, cartridge chamber filter, in-tank cartridge filter, an indexing gravity bed filter, sand filter or others. As you can see, there are a variety of mechanisms available to accomplish the same thing. The consideration typically comes down to the type of plating process one has, the number of bath turnovers necessary to keep the bath from contamination, the ease of changing filter media, the quality expected from the customer, temperature of the process and whether the plating process will normally need to be carbon polished.
CARBON FILTRATION
One of the most overlooked aspects of filtration is carbon filtration. First, let’s examine why carbon is necessary.
There are many sources of organic contamination that cause issues in a plating bath. Oils, lubricants, brightener breakdown products, buffing compounds and anode bags that have not been leached are just some of the more common sources. The common effects are dull plating deposits, roughness, pitting, adhesion issues, high current density issues and low plating thickness due to plugged anode bags.
Without getting into the technical aspects of activated carbon, the finisher should become familiar with the variety of activated carbon products available. Asterion provides direction to our clients when choosing the proper activated carbon for treating their processes. We always recommend bench testing prior to application on the filter when testing a new product.
Asterion sells a very effective product called Benchsorb 100, which is a carbon/filter aid mixture in one product. Some clients refer to it as a “wet carbon” product. It is pre-coated on a plate filter, and replaces activated carbon and filter aid for carbon polishing plating baths. The technical name of the product is EBC or electrokinetically bonded carbon. We will be happy to discuss this with you at your request.
MAINTENANCE
Maintenance of a plating bath should include, but is not limited to, scheduled and frequent filter media changes, fresh carbon packs or cartridges, regularly scheduled anode bag maintenance, attention to plugged air agitation lines, repairing or replacing damaged tanks and tank liners, replacing non-working thermocouples on thermostats and maintaining clean anode bars.
As you can see, it takes a concerted effort to clean and maintain a plating process. Let Asterion be your trusted partner when it comes to maintaining a high-quality plating process.
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