The Study Process Of Ni Based Bomposite Coatings And Corrosion Resistance In Seawater

Double Ni-P,Ni-P-Ni-Zn-P composite coating and Ni-P-SiO₂ composite coating were prepared by electroless method.The effects of complexing agents and buffers were studied on Ni-P and Ni-Zn-P base bath formulations.The effects of the electroless process on the surface morphology,section morphology and composition of the coating were studied.The corrosion resistance of the single layer and composite coating was also studied.Through the experimental study,the following conclusions are obtained.When the inner layer of phosphorus Ni-P plating 10²0min,the outer layer of highphosphorus Ni-P alloy plating 60 min,with the inner plating time increasing,the inner coating thickness increases,the inner and outer coating thickness ratio decreases,coating thickness decreases.The Ni-P composite coating can not be obtained when the inner plating time is 30 min and the outer plating time is 60 min.In the preparation of double Ni-P/Ni-Zn-P composite coating,double Ni-P/Ni-Zn-P coating can not be obtained when the inner Ni-P plating coating 5¹0min,the outer layer of Ni-Zn-P alloy plating 60 min.The Ni-P/Ni-Zn-P coatings with the total thickness of7.5?m were obtained when the inner Ni-P coating plating 20 min and the outer Ni-Zn-P coating plating 60 min.The thickness of the coating is about 2.3?m,the P content is about9%,the Ni content is about 86%;the thickness of the outer coating is about 5.2?m,the Zn content is about 5%,the P content is about 11%,the Ni content is about 84%.The thickness ratio of inner and outer layers is about 1:2.In the preparation of Ni-P-SiO₂ composite coating,with the increasing of the amount of SiO₂,Ni-P-SiO₂ composite coating surface cell size gradually decreases,and the arrangement is more compact,the coating is more flat and dense,which can improve the corrosion resistance of coatings.The hardness increases with the addition of SiO₂.In NaCl,H₂SO₄ solution composite coating corrosion rate was significantly lower than the alloy coating,The corrosion resistance of the base material can be improved.As the composite coating can significantly improve the density of the coating to reduce the porosity of the coating,double-layer composite coating between the inner and outer layers to form the original battery,which can better protect the substrate.