Discuss the sensitivity of stainless steel to crevice corrosion through a case study

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Let’s discuss the sensitivity of stainless steel to crevice corrosion through a case study: The washing tanks in the chlor-chemical section of a paper mill are made of 317L stainless steel, while the connecting bolts are made of 316L stainless steel. Since there is a common structural gap beneath the bolt head, crevice corrosion is likely to occur in solutions containing chloride ions. So, the bolt heads were covered with fiberglass. The result was the opposite: corrosion became even worse. Similarly, the trunnion of the scrubber mold is made of carbon steel with a 317L stainless steel coating. To prevent pitting in the outsourced stainless steel, the trunnion was covered with fiberglass-reinforced plastic. The results showed that it was still not successful. Analysis: Lining the inner surface of metal containers with fiberglass-reinforced plastic, and covering metal components with fiberglass-reinforced plastic, is a common method for corrosion prevention. Its purpose is to isolate the metal from the corrosive environment. As long as the selected fiberglass-reinforced plastic has excellent corrosion resistance in the operating environment and the construction quality is ensured, good protective effects can be achieved. However, when applying fiberglass reinforcement plastic coating or cladding to stainless steel equipment, caution should be exercised, especially when covering only partial areas. This is because stainless steel is highly sensitive to crevice corrosion, and covering the bolt heads with fiberglass actually creates more severe crevice areas. During construction, adhesive sagging also caused many gaps.