The application of a bright finish, especially a bright “flaw-free” finish, has been a major challenge for the metal finishing industry for decades. Successful brilliant, reflective surfaces are the result of proper basis metal selection, preplate process(es), proper application of chemically leveling deposits used under controlled conditions, post plate buffing and continuous careful handling of the product. Figure F.6 below shows the ability of leveling deposits to reduce the surface roughness of a basis material. However, note that the plated layers are still not fully level. Without a very good starting surface, a flaw-free, mirror bright surface can not be achieved.
Figure F.6: Electrolytic Leveling Deposits
Often the purchaser of a bright finish feels that the electroplating bath is the sole agent responsible for the desired appearance. Actually the bath is most often the least responsible. Proper basis metal selection which is free of macro discontinuities such as scratches or machining lines is of primary importance. Substrates that are corroded, full of porosity (often found in castings), tooling marks or handling damage require extensive preplate polishing. Polishing can often remove basis metal defects, but it is expensive. Polishing that provides consistent surface finishes of Ra <1.0 are not found at all facilities.
Even with the best substrate selection, preplate polishing and bright, leveling bath, careless handling or improper packaging can easily damage a product, causing delivery delays and substantial scrap costs. Successful application of flawless bright finishes requires coordination between customer and the metal finishing vendor. Discussion of the customer’s needs and expectations before finishing begins is crucial to providing the correct sequence of finishing steps to meet the finished products requirements.