Purpose

The purpose of this work is to provide theoretical guidance and experimental analysis for optimized cathodic protection (CP) design of low alloy steel in deep water environments.

Design/methodology/approach

In the present study, the CP criteria of 10Ni5CrMoV low alloy steel were investigated in a simulated deep water environment (350 m) regarding the theoretical protection potential and measured protection potential. The influences of hydrostatic pressure (HP) and temperature were also discussed in detail. The theoretical protection potential was analyzed with the Nernst equation, and the measured minimum protection potential was derived by extrapolating the Tafel portion of anodic polarization curves.

Findings

The results indicate that the minimum protection potential of low alloy steel shifts to a positive value in a deep-ocean environment. This can be attributed to the combined effects of HP and the temperature. Moreover, the temperature has a stronger influence compared with HP. The results suggest that the CP potential criteria used in shallow water are still applicable in the deep ocean, which is further confirmed through the SEM and x-ray diffraction analysis of the corrosion products resulted from the potentiostatic cathodic polarization experiments at −0.85 V_CSE.

Originality/value

In recent decades, successful applications of CP for long-term corrosion protection of the steel components applied at a subsea level have enabled the offshore industry to develop reliable and optimized CP systems for shallow water. However, differences in the seawater environment at greater depths have raised concerns regarding the applicability of the existing CP design for deeper water environments. Hence, this research focuses on the CP criteria of low alloy steel in simulated deep water environment concerning the theoretical protection potential and measured protection potential. The influences of HP and temperature were also discussed.

中文翻译：

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模拟深水环境中低合金钢的阴极保护标准

目的

这项工作的目的是为深水环境中低合金钢的优化阴极保护（CP）设计提供理论指导和实验分析。

设计/方法/方法

在本研究中，研究了在模拟深水环境（350 m）中10Ni5CrMoV低合金钢的CP准则，其中涉及理论保护电位和实测保护电位。还详细讨论了静水压力（HP）和温度的影响。使用Nernst方程分析了理论保护电位，并通过外推阳极极化曲线的Tafel部分得出了测得的最小保护电位。

发现

结果表明，在深海环境下，低合金钢的最小保护潜能变为正值。这可以归因于HP和温度的综合影响。此外，与HP相比，温度的影响更大。结果表明，在浅水中使用的CP电位标准在深海中仍然适用，这已通过在-0.85 V _CSE下进行的恒电位阴极极化实验产生的腐蚀产物的SEM和X射线衍射分析进一步证实。

创意/价值

在最近几十年中，CP在海底应用的钢部件的长期腐蚀防护中的成功应用使海上工业能够开发出可靠且优化的浅水CP系统。然而，更深层海水环境的差异引起了人们对现有CP设计在更深水环境中的适用性的担忧。因此，本研究着重于低合金钢在模拟深水环境中的CP标准，涉及理论保护电位和实测保护电位。还讨论了HP和温度的影响。