电镀镍–钨–磷合金在海上平台输水管道系统中的应用

Application of nickel–tungsten–phosphorus alloy prepared by electroplating to water delivery pipeline system for offshore platform

以海上平台输水管道系统用A106钢为基体电镀Ni–W–P合金。镀液组成和工艺条件为:NiSO_4·6H_2O 100~200 g/L,Na_2WO_4·2H_2O 10~100 g/L,H_3PO_3 10~50 g/L,自制YC-5202添加剂10~40 m L/L,电流密度1~10 A/dm^2,pH 2~8,温度40~80°C。研究了热处理温度对合金镀层微观结构和显微硬度的影响,并表征了合金镀层的微观形貌、结合力、耐中性盐雾腐蚀、耐H_2S腐蚀和抗冲蚀性能。随热处理温度升高,镀层由非晶态转变为晶态,显微硬度先升高后降低。Ni–W–P合金镀层表面平整、致密,结合力良好,经720 h中性盐雾试验后的保护等级为10级,经168 h H2S腐蚀试验后的平均腐蚀速率为0.007 6 mm/a,仅发生轻度腐蚀;在冲蚀试验中的损耗速率为0.656 mg/(h·cm^2),比基材的损耗速率低70%。

Ni-W-P alloy was electroplated on the surface of A106 steel applied to water delivery pipeline system for offshore platform. The bath composition and process parameters are as follows： NiSO4·6H2O 100-200 g/L, Na2WO4·2H2O 10-100 g/L, H3PO3 10-50 g/L, home-made YC-5202 additive10-40 mL/L, current density 1-10 A/din2, temperature 40-80 ℃, and pH 2-8. The effect of heat treatment temperature on microstructure and microhardness of the alloy coating was studied. The microscopic morphology, corrosion resistance to neutral salt spray and H2S, as well as erosion resistance of Ni-W-P alloy coating were characterized. With increasing heat treatment temperature, the alloy coating is transformed from amorphous to crystalline state and its microhardness is increased initially and then decreased. The obtained Ni-W-P alloy coating is smooth and compact, and has a strong adhesion strength and a protection level of 10 grade after neutral salt spray test for 720 h. Only mild corrosion occurs on alloy coating with an average corrosion rate of 0.007 6 mm/a after H2S corrosion test for 168 h. The weight loss rate of alloy is 0.656 mg/（h.cm2） during the erosion test, which is 70% lower than that of the A106 steel substrate.