Deposition Mechanism of Self-deposition Coating System.

Abstract

The deposition mechanism of self-deposition coating system for steel substrates has been investigated. The first stage of the self-deposition reaction is steel oxidation by iron (III) fluoride. The second stage reaction is resin emulsion coagulation and deposition on the steel surface by neutralizing the negative charged emulsion with positive charged iron (II) ions generated in the first stage.To demonstrate the effects of iron (II) and iron (III) ions, equilibrium calculation and simulation in concern with resin emulsion coagulation with iron (II) fluoride have been conducted.As the results, iron (III) fluoride existed as a fluoride complex with nocharge in the coating bath and did not contribute to discharging the resin emulsion. On the other hand, iron (II) fluorides in coating bath exist as hexaaqueous complexes with positive divalents, and effectively discharged the emulsion. The remarkable defference in the stability constants of iron fluorides between iron (II) and iron (III) ions consists of the self-deposition coating system.