| The steel has widespread application in the industry, but the steel's corrosion caused very serious damages. Therefore, the research about strengthening the anti-corrosive performance of the steel has very important significance to the conserve resources. The technology of electroless plating is an important method to enhance steel's anti-corrosive performance. The suitable type and quantity of rare-earth element have been added in the electroless plating bath, which can increased the stability and the service life of plating bath, reduced the temperature of electroless plating, raised the chemical deposition speed, improved the corrosion resistance.First, the research adopted the acidic plating bath. The results indicated that, the deposition rate have been elevated and after it reduced gradually along with the temperature's increased, but the phosphorus content and the pH value of the plating have straight reduced. The optimum condition of the electroless nickel plating which have been obtained through the orthogonal experiment:the concentration of Nickel sulfate is 25-30g/L, the concentration of Inferior Sodium phosphite is 25-30g/L, the concentration of Sodium acetate is 5-10g/L, the concentration of Citric acid is 15-20g/L, the concentration of Lactic acid is 5-10 g/L, the concentration of Succinic acid is 3 g/L,the concentration of Thiourea is 1～2mg/L, right concentration of Sodium hydroxide, the degree of temperature is 84～88℃, the pH value is 4.5～5.0, plating time is 1h. Through the SEM, EDS and XRD,we obtained that, the plating structure which is the amorphous state and very integrity and uniformity, has low quality of holes. The anti-corrosive performance of the nickel plating is better than the non-plating of steel.Second, we studied on the effect of added right amounts of La in the bath on the technology and coating performance of electroless plating based on the previous process conditions of electroless plating Ni-P. We obtained best recruitment of La is 15mg/L. Results show that, plating rate has been achieved in a biggest degree when the temperature on 81℃, and the plating time has been shorten greatly. In contrast to the plating temperature between added and without La, the increase rare earth can reduce plating temperature and costing, save resources.Then, the result indicated that the stability of plating bath have been increased with the pH value's reduced, have been reduced first and then increased with temperature's increased, have no change with the rised of the ratio of Ni-P, have been increased with the strengthen of the concentration of Lactic acid, have been stabled first and then decreased with the increased of the concentration of sodium acetate. The effect of the ratio of citric acid and the lactic acid, the concentration of sodium acetate and plating time on plating rate has been investigated by using the orthogonal test. United the influence of the above technological conditions on the stability of plating bath, the best technological conditions of electroless plating nickel with rare-earth element La have been obtained:the concentration of Nickel sulfate is 25-30g/L, the concentration of Inferior Sodium phosphite is 25-30g/L, the concentration of Sodium acetate is 12-25g/L, the concentration of Citric acid is 5-10g/L, the concentration of Lactic acid is 15～20 g/L, the concentration of Succinic acid is 3 g/L, the concentration of Lanthanum oxide is 10～20 mg/L, the concentration of Thiourea is 1-2mg/L, right concentration of Sodium hydroxide, the degree of temperature is 78-82℃, the pH value is 4.5～5.0, plating time is 1h.Finally, the anti-corrosive performance of plating has been studied by using the polarization curve law test,and we obtained that, the corrosion potential of the blank preview is -597mv, the corrosion potential of the plating of electroless plating Ni-P without adding La is -443mV, the corrosion potential of the plating of electroless plating Ni-P which contained rare-earth element La is -371mV, and the corrosion current of the blank preview is 9.6×10-7A·cm-2, the corrosion current of the plating of electroless plating Ni-P without added La is 1.4×10-7A·cm-2, the corrosion current of the plating of electroless plating Ni-P which contained rare-earth element La is 0.2×10-7A·cm-2. Since corrosion current in turn reduces, from corrosion potential ordinal elevated.The result indicated that the plating with best anti-corrosive performance have been obtained in the plaiting bath which it have been added right quantity of rare earth element La.
|
PDF Full Text Request