Research On Electroless Plating Ni-Fe-P And Ni-W-P On Q235Carbon Steels

The carbon steel is one of the typical material, which is commonly used in grid clampand bolt. In coastal areas, because of the corrosive atmospheric environment, the plain carbonsteel products are more likely to be corroded, leading to the final material failure. It is aserious threat to the security of grid and economic operation. Thus, it is necessary for surfacecorrosion reinforcement treatment. As a new superficial process, with cost-effective, energyefficiency and non-pollution, The electroless plating on carbon steels is a good surfacemodification to improve comprehensive performance, such as anti-corrosion, wear-resistant.Therefore, the electroless plating is important in the field of materials protection technology.The article focuses on the Q235carbon steel substrate, the system of electroless platingNi-Fe-P and Ni-W-P were systematically studied:1)Process optimization. The nickel sulfate and ferrous sulfate/sodium tungstate act asprimary salt of electroless plating Ni-Fe-P/Ni-W-P. According to the bath solution stability,thedepositing velocity, hardness of deposit,the phosphor and iron/ungsten content in alloy platingand the capability of resisting corrosion of depositing layer.Based on the result of screeningeffective component,the approach of single factor experiment is used to optimize componentsincluding primary salt,reducing agent,complexing agent,buffer agent,stabilizer,etc.On thebasis of the optimization formulation,The influences of temperature and initial pH on the bathperformance were studied.By means of comprehensive analysis,the optimal parameters andformula were obtained. the optimal parameters and formula of electroless plating Ni-Fe-P isas follow:NiSO4·6H2O30g/L，FeSO4·7H2O4.76g/L，HBO36.88g/L，(NH4)2SO424.50g/L，NaH2PO2·H2O23.59g/L，C6H5Na3O7·2H2O52.36g/L， T901℃，pH9.0；That ofelectroless plating Ni-W-P is as follow： NiSO4·6H2O30g/L， Na2WO4·2H2O40g/L，C6H5Na3O7·2H2O60.83g/L，NaH2PO2·H2O18g/L，C3H6O314.03g/L，(NH4)2SO425.68g/L，H2NCSNH20.02mg/L， T901℃，pH9.02) the micro-morphology, composition and microhardness of the typical sample isanalyzed. The micromorphology, composition and microhardness of the optimization depositing layer were analyzed by SEM, EDS and microhardness tester. Through appearanceanalysis and cross-sectional microscope observation, the results indicate that the thickness ofNi-Fe-P depositing layer can be up to16.10um, the depositing layer has compact structure;thethickness of Ni-W-P depositing layer can be up to12.68um, the depositing layer has compactstructure; Through composition analysis,the results indicate that, in Ni-Fe-P depositinglayer,the content of Fe is8.72%, the content of P is8.0%,the content of Ni is83.28%; InNi-W-P depositing layer, the content of W is5.23%,the content of P is8.31%,the content ofNi is86.40%; Through microhardness analysis, the results indicate that, the hardness ofNi-Fe-P depositing layer is up to534HV, the hardness of Ni-W-P depositing layer is up to539HV.3) the corrosion protection comprehensive performance of the typical sample wasanalyzed. Through corrosion method of laboratory immersion in3.5%NaCl solution, theresults indicate that, compared with the carbon steel substrate, the corrosion resistance ofNi-Fe-P and Ni-W-P alloy coating sample was improved greatly. The corrosion resistance ofNi-W-P depositing layer is better than that of Ni-Fe-P depositing layer.Throughelectrochemical potentiodynamic polarization, the results indicate that, the corrosion currentdensity of Ni-P-W and Ni-Fe-P depositing layer were respectively1.11%,2.12%that of theblank samples.The open circuit potential of Ni-P-W and Ni-Fe-P depositing layer were239mv and158mv higher than that of matrix.