Manufacturing steel tubing used in automobile industry, electroplates with zinc, adds passivation layer, degreases and coats with polymer by hot extrusion

摘要

The steel is electroplated with zinc. A passivation layer of trivalent chromium compounds is coated onto the zinc, then degreased in an aqueous medium and hot air dried. Aqueous epoxy resin bonding agent is applied to the passivation layer, using an immersion bath, then thermal dried and hardened. The tube is preheated prior to polymer coating by extrusion, then cooled in a water bath and quality tested. An independent claim is included for steel tubing.