Products Finishing

SEP 2018

Products Finishing magazine is the No. 1 industrial finishing publication in the world. We keep our readers informed about the latest news and trends in plating, painting, powder coating, anodizing, electrocoating, parts cleaning, and pretreatment.

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BY MESUT AKKAYA, PINAR AFSIN, MUSTAFA URGEN AND CAN AKYIL POLITEKNIK METAL SAN. TIC. A.S., COVENTYA Decreasing the concentration of aluminum in the low caustic step can also lead to problems such as preferential etching. How Dissolved Aluminum in Low Caustic Etch Baths Affects Acid-Etched Surfaces 22 SEPTEMBER 2018 — PFonline.com Aluminum and its alloys have been widely used over the past many decades, especially in the aircraft industry, due to its excel- lent weight-to-strength ratio and corrosion resistance. The need to reduce weight-to-strength ratios makes it particularly attrac- tive to the building industry, but it also is being used increasingly in the automotive industry, along with defense, ship construction, packaging, building and others. Aluminum cannot be used as produced, however, due to its amphoteric nature, by which the native oxide film on the aluminum surface tends to corrode in alkaline and/or acidic environments. It therefore has to first undergo surface treatment processes such as painting, lacquering or anodizing. Among those processes, anod- izing provides the longest surface life, with higher chemical abrasion resistance while maintaining the metallic texture of the surface. The building industry in particular requires these properties. But unlike with lacquering or painting, anodizing has a tendency to enhance any defects on the surface originated from the base metal. These defects are preferentially etched in the pretreatment step as a result of the higher chemical potential, and they resurface even stronger before PLATING

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