Study On High-speed And Bright Electroless Plating Of 6063 Aluminum Alloy Extrusion Profile

The corrosion resistance of materials is directly related to the operational safety and service life of the material products.Aluminum alloy has many advantages such as light weight,high strength,excellent forming processability,etc.It is widely used in all walks of life.However,major defects such as poor weldability,poor corrosion resistance,and poor decoration determine the importance of surface treatment technology in the forming and manufacturing of aluminum alloy products.Therefore,the study of aluminum alloy surface modification technology is of great significance to the development of aluminum alloy applications.This paper conducts researched on the 6063 aluminum alloy extruded section,aiming at researching and developing new Ni-P high-speed bright electroless plating technology.The high-speed deposition technology of Ni-P binary alloy coating had been successfully developed through functional additive screening,bath formulation and plating parameter optimization,thus creating a uniform,dense,mirror-like bright coating which strongly bonds with the substrate and was highly corrosion proof.The main research work and achievements of the paper were as follows:?1?Active ingredients of Ni-P electroless plating bath screening.Both lactic acid and citric acid could increase the plating speed while complexing the plating solution,but the acceleration effect of citric acid was more obvious.Both sodium acetate and ammonium acetate had good bath buffering capacity,which could effectively increase the plating speed,but both reduced the brightness of the coating surface.A comparative study of the effects of sodium benzenesulfinate,sodium saccharinate,C brightener,pyridine,D brightener,and lead acetate on electroless Ni-P electroless plating revealed that C brightener,D brightener and lead acetate had excellent brightening effect without slowing down the plating rate,C brightener and D brightener were combined for better plating..?2?Ni-P electroless plating formulation and plating parameters optimization.Based on the previous screening results of the active components of the bath,the plating rate,coating brightness,coating hardness,coating composition,and surface uniformity were used as the main evaluation indicators.The influence of each component and the plating parameters on the plating effect were investigated systematically.Finally the optimal electroplating solution formula and the plating parameters were obtained:nickel sulfate?NiSO₄·6H₂O?40g/L,sodium acetate?CH₃COONa?40g/L,citric acid?C₆H₈O₇?1g/L,thiourea?H₂NCSNH₂?1.5mg/L,C Brightener 4.5mg/L,D brightener 25mg/L,sodium hypophosphite?NaH₂PO₄·H₂O?70 g/L;plating solution pH 5.5,T=80°C.Under this condition,the plating speed could be up to 17.5mg/cm²·h,and the light intensity value could be up to 438 Gu.?3?Typical sample properties and composition analysis.The plating layers were separately subjected to SEM,EDS,electrochemical potentiometric polarization?PDP?and coating/substrate adhesion tests.The results showed that the aluminum alloy substrates were completely covered by the coating,and the coatings were dense without microscopic defects such as pores and cracks.The addition of the brightener was beneficial to refine the microstructure of the coatings,so that the unit cells size were smaller and the surfaces were smoother.The optimum Ni-P plating P content was 6.4wt%,belonging to the middle phosphorus plating layer.In the 3.5 wt%NaCl test medium,compared with the blank sample,E_corr of the best Ni-P plating sample and the ordinary matte plating sample shifted 694mV and656mV positively,the corrosion rate of the two were 0.13%and 2.58%of the blank samples,which indicated that the coating could significantly improve the corrosion resistance of the aluminum alloy,and the bright coating had better corrosion resistance.The plated samples were well bonded to the substrate.The cost of the best formulation bath was almost the same as the cost of commercially available industrial baths.Comparing the effects of the two processes,it was found that the best formula plating solution had better effect,so it had good prospects for industrial production.And this plating solution formula did not contain dangerous additives,so it had good safety and environmental protection.