technical case study
South Africa’s coastline remains one of the harshest environments in the world for stainless steel applications, yet industry experts argue that most failures blamed on material selection are, in fact, rooted in poor fabrication practices. Sassda has just launched a new technical guide on stainless steel passivity in South African coastal environments which urges engineers, fabricators and specifiers to rethink the way corrosion risk is assessed and managed. Passive Layer, Active Risk: Why Coastal Stainless Steel Failures Start in the Workshop
This has significant implications for commonly specified grades such as 304 and 316 stainless steel. Grade 304, which lacks molybdenum, has limited resistance to chloride attack and is generally regarded as unsuitable for coastal applications close to the sea. Grade 316 performs considerably better due to the presence of molybdenum, which improves pitting resistance and supports re-passivation of damaged areas. Yet the guide stresses that 316’s coastal performance is highly dependent on fabrication quality. Correctly fabricated components can provide excellent service life, while poorly fabricated systems may fail rapidly and visibly. Duplex stainless steels offer the highest level of corrosion resistance owing to their elevated chromium, molybdenum and nitrogen content. Nitrogen, in particular, significantly improves re-passivation kinetics and localised
At the centre of the discussion is the passive layer, the ultra-thin chromium-rich oxide film that gives stainless steel its corrosion resistance. While the alloy itself may contain as much as 70% to 80% iron, it is this microscopic passive layer that prevents corrosion by blocking metal dissolution and continuously reforming in the presence of oxygen. However, in coastal South African conditions, maintaining that passive layer is far more difficult than many project teams appreciate. The combination of high chloride exposure, strong prevailing winds, warm temperatures and daily wet-dry cycles creates an aggressive environment where even small fabrication defects can rapidly develop into visible corrosion. According to the guide, these conditions expose “fabrication sins” within months rather than years.
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Issue 2 – 2026
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