Research On Electroplating Zn-Ni-P/Nano-SiO₂ Composite Coating

The research of this paper is based on Zn-Nialloy,P element and nano-SiO₂ particles are co-deposited into the Zn-Nialloy coating to further improve the corrosion resistance and wear resistance of the coating,In order to broaden the application field of Zn-Nialloy.The main research contents and conclusions of this article are as follows:???Orthogonal experiment in the Hull Cell was used to optimize the formulation and process of acetate-ammonium system electroplating Zn-Nialloy,The optimization results are:ZnCl₂ 80g/L?NiCl₂·6H₂O 120g/L?CH₃COONH₄ 80g/L?CH₃COONa30g/L?EDTA-2Na4g/L?KCl 180 g/L?SDS 0.08g/L?pH 5,T 45??I 1A?Addition of NaH₂PO₂ as the P source to the optimized Plating formula,and the deposition behavior of Zn?Niand P were analyzed by cyclic voltammetry.The results showed that:when only NaH₂PO₂·H₂O exists in the base solution environment,P can not be reduced,The addition of NaH₂PO₂·H₂O is benefit to the deposition of Niand has no obvious effect to the deposition behavior of Zn.The effects of process conditions on P deposition are:the current density has the most significant effect on the deposition of P elements,and a high P content coating?P>10wt%?is obtained within the current density range of 0.4A/dm²?0.6A/dm²,and a low P content coating?wt%P<1?will be obtained when current density more than the1A/dm².Increasing the temperature and lowering the pH are favorable for the deposition of P.The electrochemical test and neutral salt spray test were used to test the corrosion resistance of the coating,and the hardness of the coating was tested using a micro hardness tester.The results show that the Zn-Ni-P?P wt%<1?coating shows the best corrosion resistance.And highest microhardness.The morphology and composition of the coating were analyzed,SEM,?EDS,?XRF?XRD test results show:the addition of NaH₂PO₂·H₂O can completely eliminate the micro-cracks of the coating and refine the coating crystal;the Zn-Ni-P?P wt%<1?coating composition content is Zn79.3 wt%,Ni18.4 wt%,P 0.8 wt%?remainder Fe and O?,the phase composition of the coating is mainly?-phase Ni5Zn21.???Nano-SiO₂ was used as dispersed phase particles,a surfactant was used as a dispersing aid,and ultrasound was used as a physical assistant to disperse,Zn-Ni-P/nano SiO₂ composite coatings were prepared by electroplating.The optimum addition amount of nano-SiO₂ was determined to be 5g/L.Three types of surfactants were tested.The research conclusion is 0.4g/L cationic surfactant CTAB and 0.6g/L PEG-6000 can significantly improve the composite amount and embedding state of nano-SiO₂ in the coating;the optimal plating temperature was 45?,the optimal stirring rate was 250 rpm,and the optimal ultrasonic dispersion treatment time was 3 hours.and the state of particles intercalation is the best,the content of Nano-SiO₂reaches the maximum,The content analysis of the coatings by EDS was Zn77.5 wt%,Ni19.2 wt%,P 0.86 wt%,and SiO₂ 1.41 wt%.???The effect of different heat treatment temperatures on the properties of the coating was studied.Electrochemical tests and neutral salt spray experiments were used to test the corrosion resistance of the coating.The results showed that after 300?heat treatment,the coating had the most positive corrosion potential,the lowest corrosion current,the largest capacitance resistance arc,The time of the red-Corrosion products appears in the neutral salt spray experiment reaches the maximum of 255 hours,and t Shows the best corrosion resistance performance.After heat treatment at 300°C,the matrix metal of the composite coating is fine and smooth,nano-SiO₂ is best for intercalation,Fine-grained coating,and the microhardness of the composite coating reaches a maximum of 245HV.