黄铜冷凝管的点蚀

中国腐蚀与防护学报, 1985, 5(4): 241-249.

黄铜冷凝管的点蚀

中国科学院长春应用化学研究所

ON THE PITTING CORROSION OF BRASS CONDENSER TUBE

Shan Yibin , Chang Yugin , Lin Haichao , Ban Mingzhao Changchun Institute of Applied Chemistry

研究了 H68 A 黄铜在含 Cl~-溶液中的闭塞阳极行为。结果表明,黄铜的闭塞阳极不存在加速腐蚀的自催化效应,而是使闭塞区表面保持活性状态。其电位随阳极液 Cu~+浓度升高而变正。闭塞区Cu~+和 H~+不能向外扩散时,EE_(Cu/CuCl/Cl~-)进行生成 CuCl[s]的溶解反应。Cu~+和 H~+能向外扩散时,E>E_(Cu/Cu_2O/h 即能发生溶解。此时闭塞室内生成 Cu_2O。闭塞区外有扩散出来的 Cu~+经二次反应后生成的沉积物。黄铜冷凝管点蚀的腐蚀产物分布情况符合后者,这种点蚀在 E>E_(Cu/Cu_2O)时即能形成。黄铜管表面有碳膜时容易形成闭塞区并使电位升高,起到促进点蚀发生和加速点蚀作用,而不是产生点蚀的必要条件。为防止点蚀必须促使黄铜表面生成完整的保护膜。

The anodic behaviour of H68A brass in occluded condition was investigated. It is shown that in the occluded area the surface of brass remains in active state,butno autocatalytic dissolution effect can be detected.The potential of brass in occluded area becomes more noble as the concentration of Cu~+ in anolyte increases.If H~+ and Cu~+ can not diffuse outwardly from occluded area, the anodic dissolution of brass in occluded area can not take place when EE_(Cu/CuCl/Cl~-).On the other hand,if H~+ and Cu~+ can diffuse outwardly from occluded area,the anodic dissolution occurs at potential above E_(Cu/Cu_2O/H~+.The product of anodic dissolution in cavity is Cu_2O.At the same time,there are deposits formed at the mouth of the cavity by secondary reactions of Cu~+ diffused outwardly from cavity. The distribution of the corrosion products within and over the pits on brass conpenser tubes seems the latter case as mentioned above,so Cu~+ and H~+ ions must diffuse from pits toward outside in the pitting corrosion process of brass tube and hence these pits can be formed when E

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