Long life protective coating for transformer tanks - using phosphate coating, then electrostatic spraying of powdered plastic

摘要

A high quality protective coating is obtd. on metal objects with a complex shape. The novelty is the use of two simple operations: (a) phosphate coating and (b) electrostatic spraying of a powdered organic polymer via a compressed air pistol. The powder coating (b) is pref. obtd. by sweeping hollow zones forming a Faraday cage. The thermoplastic or thermosetting powders deposited to form coating (b) are pref. cured by heating, possibly combined with radiation; and coating (b) may be below 60 mum or above 100 mu m thick depending on the coating and the type of substrate. The finished coating pref. has a resistance of min. 1000 hours in the 5% salt spray test to NF X-41002; and is pref. employed on corrugated transformer tanks exposed to the open air over several years. The process is simple and costs less than the conventional Zn coatings.