Study on Some Critical Factors for the Electroless Composite Plating

In order to make the electroless Ni-P coating possesses the better hardness,wear and corrosion resistance,Ni-P-nanometer Al_2O_3 composite coating is prepared by electroless composite plating.The influences of some critical factors,such as temperature,pH value and the ratio of powder in the solution,on the solution stability,the deposition rate and the content of phosphate in the coating are studied,especially,the various dispersing methods for the powder are deeply studied.The results indicate that the electroless composite coating with good properties can be obtained under the proper technical conditions as following : pH value in the solution is 4.4～4.6,the temperature of the electroless plating is 90±2℃,the concentration of Al_2O_3 particle is 12～14g/L,and using the mechanical stirring of 200～250r/min as well as the ultrasonic dispersing of the frequency 40kHz.