A New Process For The Pretreatment Of Electroless Nickel Plating On Aluminum Alloys

Aluminum alloy as a new generation of high performance light metal material,which has a light weight,high strength,good electromagnetic shielding and conduc-ive performance and are easy to be recycled,technology is more and more widely applied.But poor corrosion resistance has been blocking aluminum alloy aluminum alloy large-scale application of technical bottleneck. Through the current aluminum alloy surface treatment is the means to improve the corrosion resistance.Chemical nickel plating process after the second zinc leaching process are the shortcomings of mad,leaching of zinc layer Zn2+ will be in the process of plating into chemical nickel plating liquid,make the performance of the plating solution continued to deteriorate,service life is greatly reduced,affecting the performance of the nickel plating layer.There is a big significance in the research with an immersion nickel-pre nickel plating pretreatment process instead of a second dip zinc-nickel plating pretreatment technology.The concrete research content is as follow:(1) The unoil formula and the optimum technological conditions were determined:sodium carbonate 25g/L and sodium phosphate 25g/L,dodecyl benzene sulfonic acid sodium2g/L,unoil temperature is 50 ℃,unoil time 5 min;(2) The alkali corrosion fluid formula and the optimum technological conditions were determined:sodium hydroxide 50g/L,sodium dodecyl benzene sulfonic acid 2g/L(surfactant),alkali corrosion temperature 50℃,alkali corrosion time 10s;(3) The light fluid formula and the optimum technological conditions were determine:50% HNO3,the remaining 50% of the water,the time of 30 s,the light at room temperature;(4) The nickel leaching liquid formula and the optimum technological conditions were determined: nickel sulfate 300g/L,boric acid 30g/Lhydrofluoric acid25mg/L,nickel leaching temperature under normal temperature,immersion ni time 40s;(5) The nickel plating liquid formula and process conditions were determined:nickel sulfate 25g/L,sodium hypophosphite 25g/L,sodium pyrophosphate 50g/L,cerium sulfate 6mg/L,potassium iodide 20mg/L,precoated time 5min,precoated temperature at room temperature;(6) Compared to traditional secondary zinc leaching pretreatment process after electroless nickel plating coating performance,a leaching of nickel aluminium alloy electroless nickel plating pretreatment new process is feasible.