Stress corrosion cracking (SCC) testing was conducted on pipeline steels to investigate the transition from near-neutral to high-pH environments via solution evaporation and concentration. The study clarified the roles of sulfate and bicarbonate in enhancing crack dissolution and their impacts on SCC. In sulfate-absent concentrated solutions, intergranular branching primarily resulted from direct propagation from the crack tip, accompanied by microcrack coalescence. The presence of sulfate effectively halted further growth by inducing crack-tip blunting, thereby reducing the mechanical driving force for crack propagation. This explanation clarifies why regions ideal for SCC exhibit no reported incidents, offering strategies for SCC mitigation.

中文翻译：

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从近中性环境到易受应力腐蚀开裂的高 pH 环境的演变：硫酸盐和碳酸氢盐的作用

对管线钢进行应力腐蚀开裂 (SCC) 测试，以研究通过溶液蒸发和浓缩从近中性环境到高 pH 环境的转变。该研究阐明了硫酸盐和碳酸氢盐在促进裂纹溶解方面的作用及其对 SCC 的影响。在不含硫酸盐的浓溶液中，晶间分支主要是由裂纹尖端直接扩展引起的，并伴有微裂纹合并。硫酸盐的存在通过诱导裂纹尖端钝化有效地阻止了进一步的生长，从而降低了裂纹扩展的机械驱动力。这一解释阐明了为什么 SCC 理想区域未报告任何事件，并提供了缓解 SCC 的策略。