The Electroplating Palladium-Copper Alloy Film On 316L Stainless Steel And Its Corrosion Resistance In Mixture Of Acetic And Formic Acids

This thesis is aimed at the low corrosion resistance of 316L stainless steel in mixture acetic and formic acids containing 400 ppm Br^-.A new method of electroplating Palladium-Copper alloy films on 316L stainless steel was carried out in order to enhance the corrosion resistance of 316L stainless steel in mixture acetic and formic acids containing 400 ppm Br^-.Also,in order to have a good realization of the Palladium-Copper alloy films,the appearance, the composition and the structure of the films were studied and the micro hardness were measured.Corrosion behaviors of the palladium-copper plated samples in acetic and formic acid mixtures at boiling temperature were studied. Finally,the reasons of the Palladium-Copper alloy films enhance the corrosion resistance of 316L stainless steel in mixture acetic and formic acids containing 400 ppm Br^- were discussed.Different Palladium-Copper alloy films were obtained through altering the content of EDTA·Cu.EDX was used to determine surface compositions of the palladium-copper alloy films and the compositions of single grain in the Pd-Cu alloy films.The result showed that it was a line relationship of copper content in the palladium-copper alloy film with Cu²⁺ concentration in the electroplating solution and the distribution of copper in the alloy film was more or less uniform.The palladium-copper alloy films were more compact than palladium films by the test of Porosity and surface appearance.XPS analysis indicated that palladium and copper in the film surface were present in the form of metallic state.XRD analysis indicated that palladium-copper solid solution alloy films were obtained as a result of some Pd atoms being replaced by some Cu atoms in the lattice of palladium.The adhesive strength was examined by cross-cut tape test,thermal shock test and Cross-cut tape test,and the adhesion of the film to stainless steel was quite good.The micro-hardness of the palladium-copper film was much higher,compared with the stainless steel and palladium film,and it was enhanced with the increased of copper content in the film.The palladium-copper alloy film(Cu 5.66%) has a good corrosion resistance in mixture acetic and formic acids containing 400 ppm Br^- by polarization tests, electrochemical impedance tests and weight loss tests.The effect of copper in the palladium-copper alloy film was discussed by comparing the capability of palladium-copper alloy films and palladium films.