Study On Extraction Of Organic Acid And Its Application In Copper Foil Conversion Film

Copper is widely used because of its excellent electrical and good mechanical properties,but it will corrode and discolor during use,thus seriously affect the performance and life.At present,chromate passivation film is the common protective film on copper foil.However,the chromate passivation solution containing hexavalent chromium,which can destroy the DNA structure of human and animal,limits its industrial application.Therefore,it is of great practical significance to develop a chromium-free passivation solution for copper foil.Although a lot of research work has been done on non-chromate protection technology at home and abroad,there is still no better method to replace chromate passivation film.Because of the advantages of high temperature resistance,corrosion resistance and easy access,organic acids have shown a broad application prospect as film-forming agents in metal surface protection.The extraction of organic acids from biomass wastes not only opens up a cheap source of organic acids,but also improves the high-value utilization of wastes.Therefore,in this paper,phytic acid was extracted from rice hull and citric acid was extracted from lemon dregs,the corrosion resistance and high temperature resistance of passivation solution on copper foil were investigated:（1）phytic acid was successfully extracted from rice husk by acid extraction,and composite passivation film was prepared on the surface of copper foil with phytic acid as film-forming agent.The results showed that the extraction rate of phytic acid was14.98%.The optimum formula and technology of the compound passivation solution are as follows:additive P 0.05 g/L,glucose 4.0 g/L,phytic acid 1‰,inorganic salt film-forming Agent B 4.0 g/L,constant temperature water bath 30℃,conversion time 15 seconds.The surface of the film is striped and the passivation film is uniform and compact.Compared with copper substrate,the corrosion current density decreased from 13.38×10^-5 A·cm^-2 to 3.219×10^-5 A·cm^-2.The passivation film improved the corrosion resistance of copper foil.At 160℃,the high temperature resistance for 10 minutes is similar to that of chromic anhydride passivation film.（2）citric acid was successfully extracted from lemon dregs by the method of calcium hydrogen citrate,and the composite passivation solution was prepared with citric acid as film-forming agent.The results showed that the citric acid extraction rate was 12.27%.The optimum formulation and technology of citric acid composite passivation solution are as follows:polymer film-forming agent a 0.62 g/L,citric acid4.0 g/L,inorganic salt film-forming Agent B 4.0 g/L,constant temperature water bath30℃,conversion time 15 seconds.The surface morphology of the film is similar to that of chromate,but the surface uniformity is slightly worse than that of chromate passivation film.Compared with the copper substrate,the corrosion current density decreased from 13.38×10^-5A·cm^-2 to 8.122×10^-5A·cm^-2,indicating that a passivation film was formed in the passivation solution of citric acid,and has better high temperature resistance performance.