Corrosion resistance of Ni-P amorphous composite coating in the environment containing H₂S/CO₂

A multilayer amorphous Ni-P composite coating with a potential difference above 160 mV was prepared in the same bath by varying the temperature, pH value and electric field alternately. The anti-corrosion behavior of the composite coating was studied in the environment with H₂S and CO₂, and the results show that the terrace amorphous Ni-P composite coating performed well in corrosion-resistance in the environment with H₂S and CO₂. An even corrosive film formed on the surface of the composite terrace coating after 100 h. Corrosive cracks appeared on the composite coating's surface after 300 h, and the cracks expanded along the parallel direction of the base. The enrichment of phosphorus occurred in the places where the electrodeposited coating was deprived. The corrosion results indicated that this multilayer Ni-P coating of 12 μm thickness possessed better anti-corrosion properties than the plain eleclroless coating of 25 μm.