Cyanide-Free Electrodeposition Of Ag-C Alloy

With the development of modern science and technology, composite materialsbecome more and more important. Composite materials will replace the single material tomeet some special requirements. Ag-C alloy with their excellent properties of silver andgraphite, keeping the silver good conductivity and chemical stability, at the same time,improve their abradability and self-lubricating property, and reduces the amount of silver.However, graphite as a natural hydrophobic substance, it will settlement quickly when it isin aqueous solution, looking for suitable dispersant on the hydrophilic modification ofgraphite is imminent.The effects of some kinds of dispersant agents containing different concentration ondispersion of graphite in water were studied by spectrophotometer. Three kinds ofcompound dispersant(SGDF1、SGDF2、SGDF3) was obtained. Research the effect of thestability of graphite in water which adds compound dispersant agents with pH and stewingtime increased. Anti-tarnish performance test, polarization curve, AC impedance andwearing test were used to study dispersing agent SGDF1, SGDF2, SGDF3 on Ag-Ccomposite coating performance. X-ray diffraction, scanning electron microscopy and otherexperimental means were used to study crystal structure and surface morphology of Ag-Ccomposite coating.Results show that the dispersion of graphite in water maintains at high levels when pHvalue is a more than seven, and when pH is nine, absolute value of Zeta potential is thehigher, absorbency is the larger, and the stability of dispersion is the better, the degree ofconcentration that add dispersant graphite is significantly weakened than that less adddispersant graphite. The Graphite gathered minimized and the dispersion of the graphite isup to the best when adds SGDF3.Graphite was added in the basis of cyanide-free silver plating liquid, with increaseingof graphite, carbon content increases gradually in the coating and abrasion resistance ofreinforced. In composite electrodeposition solution respectively, adding a dispersingagent(SGDF1、SGDF2、SGDF3), the deposition rate and the percentage of carbon in coatings both increased, the corrosion resisting property, anti-tarnish performance andabradability all better than the coatings without dispersing agent, the coatings becomemore smooth, and the preferred orientation of silver changed after adding dispersing agent.The best coatings are the liquid with SGDF3.