Nickel-tungsten Alloy Plating Process In Alkaline Bath

With the stricter control of hard chrome plating technology,the substituting for hard chrome technology has made greater progress.Nickel-tungsten alloy has attracted attention because of its series of advantages such as low pollution and high hardness.In this subject,nickel-tungsten alloy was prepared by using nickel sulfate and sodium tungstate as main salts under alkaline conditions.Using a combination of single-factor experiment and orthogonal experiment,the tungsten content and hardness of the coating are the main indicators,and the composition and process parameters of the plating solution are optimized.If the current density is too large,the surface of the coating is easy to scorch,and if the content is too low,the tungsten content will decrease,so the optimal current density is 6 A/dm~2.Sodium tungstate is the main salt.If the concentration is too low,the tungsten content and performance of the coating will not meet the standard.If the concentration is too high,the cost will rise.The best concentration of sodium tungstate is 62.6 g/L.Using citric acid as the complexing agent,the optimal concentration is 65 g/L.Sodium saccharin,1,4-butynediol and LB low foam wetting agent are used as additives.Through orthogonal experiments,it was found that sodium saccharinate had a greater influence on the coating.The concentration of sodium saccharin was 0.5 g/L,the concentration of 1,4-butynediol was 0.1 g/L,and the concentration of LB low foaming agent was 0.5 m L/L.Ammonia can not only adjust the p H,but also affect the complexation as a secondary complexing agent.When the p H value is 8,the tungsten content and thickness of the coating are higher.When the bath temperature is 80°C,it has the maximum hardness and tungsten content.The nickel-tungsten alloy must be heat-treated to achieve a hardness comparable to that of hard chrome plating.Argon gas was used as the protective gas,the heat treatment temperature was 400°C,and the time was 1.5 h.The nickel-tungsten alloy after heat treatment has no cracks and the hardness reaches1050 HV.Electrochemical research on the co-deposition process of nickel-tungsten alloy shows that the electrodeposition of nickel-tungsten alloy is controlled by electrochemical polarization and the co-deposition is completed in one step.In this project,the study of electrochemical stripping of nickel-tungsten alloy using sodium nitrite.When the concentration of sodium nitrite is 250 g/L,the anode current density is 6 A/dm~2,and the temperature of the stripping solution is 90°C,the stripping time is the shortest,and the surface after stripping is smooth.The nickel-tungsten alloy electroplating line is designed.While paying attention to high efficiency and high quality electroplating,more attention is paid to environmental protection research.In the electroplating process,cleaning is the main water-consuming process.Therefore,three-stage countercurrent washing was adopted,and the first-stage washing was carried out by spray washing.At the same time,the first-level washed water can be added to the Plating bath.The consumption of each component during electroplating was calculated,and the detection method and addition amount of the component content were also studied.At the same time,it lists some reasons and solutions for the problems that may occur during the long-term use of the plating solution.