Carboxylic acids with different carbon chains have different corrosion behaviors on copper tubes. In this paper, corrosion behavior and corrosion mechanisms of copper tubes in formic acid (HCOOH) and acetic acid (CH₃COOH) were analyzed by vapor corrosion tests, electrochemical tests, contact angle examination, optical microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. The corrosion process of copper tubes in the HCOOH environment is more complex than in the CH₃COOH environment and HCOOH is easy to cause “ant nest” corrosion on copper tubes. The corrosion rate is faster and the surface of the copper tube is more easily corroded in the CH₃COOH environment due to the formation of unstable and loose corrosion products, Cu(OH)(CH₃COO)₂·2H₂O. The results of the contact angle examination showed that the contact angles of HCOOH and CH₃COOH on copper tube surface were 25° and 9°, respectively, which means that CH₃COOH is more likely to be absorbed by the surface of the copper tube evenly. Differences in the wettability of these two carboxylic acids with copper tubes are the main reason for the different corrosion phenomena. The corrosion mechanisms of copper tubes in carboxylic acid are also discussed.

中文翻译：

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铜管在甲酸和醋酸环境下的腐蚀行为比较

不同碳链的羧酸对铜管有不同的腐蚀行为。本文通过蒸气腐蚀试验、电化学试验、接触角检测、光学显微镜、傅里叶变换红外光谱、X射线等分析了铜管在甲酸（HCOOH）和乙酸（CH ₃ COOH）中的腐蚀行为和腐蚀机理。-射线衍射。铜管在 HCOOH 环境中的腐蚀过程比 CH ₃ COOH 环境中更为复杂，而且 HCOOH 容易对铜管造成“蚁巢”腐蚀。腐蚀速度更快，铜管表面在CH ₃ COOH环境中由于形成不稳定的松散腐蚀产物Cu(OH)(CH₃ COO) ₂ ·2H ₂ O。接触角检测结果表明，HCOOH和CH ₃ COOH在铜管表面的接触角分别为25°和9°，这意味着CH ₃ COOH更容易被铜管表面均匀吸收。这两种羧酸与铜管的润湿性不同是产生不同腐蚀现象的主要原因。还讨论了铜管在羧酸中的腐蚀机理。