Preparation Of Chrome-free Passivating Film On The Electroplated Nickel And Performance

At present, anti-rust oil, anti-rust liquid and chromate were the universal passivation raw materials for electroplated nickel layer. However, anti-rust oil possessed many drawbacks such as refractory, higher viscosity, thick oil film, influencing the appearance and the aftertreatment of products. At the same time, anti-rust liquid included sodium nitrite brought the problem of toxic and carcinogenic as well as chromate passivation, which were being stringently limited and be banned by environmental regulations for continuous use in coating processes. For these reasons, this article proposed three water-borne chromium-free passivating solutions and further researched as follows:1. An optimal hydrolysis conditions for KH-550and A-1170and their anticorrosive effect on the electroplated nickel were studied and also compared the anticorrosion performance of single-layer silane treated and double-layer epoxy resin emulsion treated. It was found from the result of Infrared spectra that KH-550could hydrolyze and generated an abundance of silanol, then condensated into-Si-O-Si-covalent bond. The test results showed that corrosion resistance performance of the panels treated with silane and epoxy resin emulsion were better than the naked one:the corrosion current density and corrosion rate induced two orders of magnitude, the anticorrosion performance of the panel epoxy resin emulsion treated was the best for the Ecorr increased by0.25V.2. A water-borne organic-inorganic corrosion inhibitor passivation technology was studied with the raw material of thiourea, sodium hexametaphosphate and heptahydrate zinc sulphate. The passivation formula and passivation technology were investigated with orthogonal test, and then further characterized the corrosion resistance. Tafle, EIS curve and SEM results showed that a dense film was formed on the nickel surface and the corrosion resistance performance was improved as the Ecorr increased0.2V; the corrosion current density and corrosion rate also changed over one order of magnitude; the corrosion inhibiting efficiency attained to95%. 3. Anti-rust oil emulsion was obtained by emulsifying the experimental anti-corrosive oil, and the passivation technology was also explored. The anticorrosion performance of the panels including naked sample and treated with anti-rust oil emulsion and market anti-rust oil were characterized and analyzed by Tafle curve and SEM. It could be seen that the Ecorr of the panel treaded with anti-rust oil emulsion exceeded nearly0.25V, along with the corrosion current density and corrosion rate reduced three orders of magnitude. As a matter of fact, corrosion resistance performance of the panel treated with anti-rust oil emulsion was highly improved.