Purpose

The purpose of this paper is to investigate the electrochemical corrosion behavior of type 444 stainless steel (SS) in synthetic tap water from 25°C to 80°C, i.e. the operation environment of the electric water heater.

Design/methodology/approach

The corrosion behavior was studied by using electrochemical measurements such as electrochemical impedance spectroscopy and polarization curve. The specimen surfaces were observed with scanning electron microscopy. The passive films were characterized with X-ray photoelectron spectroscopy.

Findings

In the typical tap water, 444 SS passivates spontaneously under different temperatures. The passive films formed at higher temperatures contain relatively less Cr-species and more Cl⁻ ions, resulting in lower polarization resistances. The stable pitting corrosion takes place in the potential region of oxygen evolution as the temperature increases to about 55°C. The critical Cl⁻ concentration of pitting corrosion reduces from about 160 mg L⁻¹ to 60 mg L⁻¹ with changing temperature from 25°C to 80°C.

Practical implications

The pitting corrosion probability was assessed through the statistical analysis of tap water quality. The results are useful for the application of 444 SS as well as the design of electric water heater.

Originality/value

This paper shows the variation of polarization resistance, pitting potential, passive film composition and critical pitting chloride concentration with the temperature of tap water. It is of great significance for the development and application of SS in tap water environments.

中文翻译：

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444型不锈钢在不同温度下在合成自来水中的电化学腐蚀行为

目的

本文的目的是研究444不锈钢（SS）在25°C至80°C的合成自来水中，即电热水器的运行环境中的电化学腐蚀行为。

设计/方法/方法

通过使用电化学测量，例如电化学阻抗谱和极化曲线，研究了腐蚀行为。用扫描电子显微镜观察样品表面。用X射线光电子能谱表征无源膜。

发现

在典型的自来水中，444 SS在不同温度下会自发钝化。在较高温度下形成的钝化膜包含相对较少的Cr-物种和更氯^-离子，从而导致较低的极化电阻。当温度升高到约55°C时，稳定的点蚀发生在氧气释放的潜在区域。临界氯^-点蚀的浓度减少了从约160毫克的L ^-1至60毫克的L ^-1从25℃至80℃变化的温度。

实际影响

通过自来水水质的统计分析评估点蚀的可能性。研究结果对于444 SS的应用以及电热水器的设计非常有用。

创意/价值

本文显示了自来水温度下极化电阻，点蚀电位，钝化膜组成和临界点蚀氯化物浓度的变化。这对于自来水环境中SS的开发和应用具有重要意义。