Effect of Cd2+ content in plating solution on composition and corrosion resistance of Ni-Cd alloy plating
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摘要: 采用电刷镀的方法在钢铁构件表面镀覆一层 Ni-Cd 合金镀层,从而实现牺牲阳极和机械保护法的双重保护机制;采用控制变量法研究镀层中不同浓度的Cd2+对于镀层耐蚀性能的影响。通过极化曲线、电化学阻抗谱、全浸腐蚀实验以及盐溶液周浸实验分别测定不同Cd2+浓度下镀层的腐蚀电位、极化电阻以及耐蚀性能。结果表明:当Cd2+摩尔分数从0.5%~5 %变化时可以实现镉质量分数为15%~90%的 Ni~Cd 合金的共沉积;其中,当 Cd2+ 摩尔分数为4 % 时,即镀层中镉质量分数为69.40 %时,合金刷镀层的耐蚀性最好。
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关键词:
- Ni-Cd 合金镀层 /
- 电刷镀 /
- 耐蚀性
Abstract: A Ni-Cd alloy plating is applied to the surface of steel component by brush plating, which can realize the double protection of sacrificial anode by cathodic protection and mechanical protection. The effect of concentration of Cd2+ in plating solution on the corrosion resistance of the plating was studied by using the control variable method. The corrosion potential, polarization resistance and corrosion resistance of the coating with different concentrations of Cd2+ were measured by polarization curve, AC impedance spectroscopy, full immersion corrosion test and salt solution immersion test. The results show that the co-deposition of Ni-Cd alloy with Cd of mass fraction of 15%-90t% can be realized when the mole fraction of Cd2+ changes from 0.5%-5 %, which belongs to abnormal co-deposition. When the molar fraction of Cd2+ is 4 %, that is, the mass fraction of Cd2+ in the coating is 69.40 %, and the corrosion resistance of the alloy brush coating is the best.-
Key words:
- Ni-Cd alloy plating /
- brush-plating /
- corrosion resistance
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图 3 不同Cd2+摩尔百分数条件下Ni-Cd合金电刷镀层的极化曲线 (a)自腐蚀电位正于基体的样品的极化曲线;(b)自腐蚀电位负于基体的样品的极化曲线
Figure 3. Polarization curves of Ni-Cd alloy plating with different Cd2+ of mole fractions (a) polarization curves with a positive self-corrosion potential to the steel substrate; (b) polarization curves with a negative self-corrosion potential to the steel substrate
表 1 镀液组成
Table 1. Composition of plating solution
Component Concentration/(g·L−1) CdSO4•8/3H2O 1.0-15 NiSO4•6H2O 220-235 C6H5O7Na3•2H2O 40 NiCl2•6H2O 30 (NH4)2SO4 5 C10H14N2O8Na2•2H2O 15 表 2 不同Cd2+摩尔分数条件下Ni-Cd合金电刷镀层的腐蚀电化学参数
Table 2. Corrosion electrochemical parameters of Ni-Cd alloy plating with different mole fractions of Cd2+ in plating solution
Mole fraction
of Cd2+/%Mass fraction
of Cd/%Ecorr/
mVicorr/
(μA·cm−2)Pure Ni 0 −403 4.351 0.5 8.12 −404 4.177 1.0 17.68 −401 3.775 1.5 22.97 −452 6.081 2.0 28.36 −459 5.934 (Substrate) — −462 11.96 2.5 36.05 −465 5.187 3.0 45.62 −517 3.649 3.5 62.73 −491 2.091 4.0 69.40 −568 0.710 4.5 85.64 −706 3.813 5.0 83.20 −628 6.443 (Pure Cd) 100.00 −835 15.50 表 3 失重法表示的腐蚀速率结果
Table 3. Results of corrosion rate expressed by mass-loss method
Mole fraction
of Cd2+/%Mass
loss /mgTest
area /m2Immersion
time /hCorrosion rate /
(mg·m−2·h−1))0.5 5.45 0.04 168 0.811 1.0 4.23 0.04 168 0.629 1.5 7.15 0.04 168 1.064 2.0 8.75 0.04 168 1.302 2.5 8.65 0.04 168 1.287 3.0 7.40 0.04 168 1.101 3.5 3.30 0.04 168 0.491 4.0 3.13 0.04 168 0.466 4.5 8.00 0.04 168 1.190 5.0 8.03 0.04 168 1.195 (Substrate) 14.72 0.04 168 2.191 表 4 Ni-Cd合金电刷镀层及钢铁基体的周期浸蚀性能
Table 4. Periodic etching performance of Ni-Cd alloy plating and steel substrate
Mole fraction
of Cd2+/%Area corroded
after 96 hArea corroded
after 192 h0.5 25% 30% 1.0 10% 20% 1.5 15% 20% 2.0 20% 30% 2.5 25% 40% 3.0 20% 50% 3.5 30% 40% 4.0 5% 10% 4.5 30% 45% 5.0 40% 55% Substrate 50% 80% -
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