Study On Effects Of Galvanized Post-processing And Flash Ni Plating On Corrosion Resistance Of Cold Rolled Steel Sheets

In recent years,with the rapid development of the our national economy,the market demand for high-quality cold-rolled steel sheet from the automobiles,household electrical appliances,aviation industries etc.is increasing year by year.The cold-rolled steel sheet has become the main products of iron and steel industry.Because the downstream industry needs to the sheets to be painted,plated and stamped,etc.,and the corrosion on the surface of cold-rolled steel sheet will seriously affect the quality and performance of subsequently processed product,the strict requirement on the corrosion resistance of the cold-rolled steel sheet surface is proposed.In the present paper,the characterization and analysis on the corrosion resistance of the galvanized cold rolled steel sheet post-treated in different ways and the flash Ni plated cold rolled steel sheet were carried out by metalloscope,scanning electron microscope(SEM),electrochemical workstation,X ray diffraction(XRD),drip experiment and so on,and combined with the production practice,the strong evidence for the improvement of corrosion resistance was provided.1.Neutral salt spray test,lead acetate spot test,NaCl solution immersion test,hot and humid test,atmospheric coupon test,all of those is the effective way to detect the corrosion resistance of the steel sheets.For the same set of samples,a variety of test method is consistent with the conclusion.2.Using a variety of methods for corrosion resistance test,the metallographic and SEM observation,the electrochemical polarization curve and electrochemical impedance spectroscopy analysis.All of those obtain the same conclusions:hot galvanizing&passivation>electrogalvanizing&phosphating and as well as blockage>electrogalvanizing&phosphorization>no treatment after hot dip galvanized>no treatment after electrogalvanized.3.Under the condition of laboratory obtain the following conclusions:The flash plating temperature between 45 and 55?,Current density is between 3 and 6 A/dm2,The flash plating time is between 15s and 20s,The surface microstructure start to change.The substrate surface nickel content more than 40.1%.Corrosion tests,steel plate surface morphology observation,electrochemical performance analysis etc,shows that flash plating nickel can improve the corrosion resistance of steel sheet.3.Under the condition of mass production,the conclusion shows that:Flash plating nickel improve the surface potential,reduce the Mn,Si,O elements enrichment,while improving the corrosion resistance of steel sheet.Different flash plating nickel content has influence on the corrosion resistance of steel plate,the more the amount of nickel plating,the better of the corrosion resistance.