technical insight
qualities. Austenitic stainless steels (300 series) are especially well-suited to the harsh conditions found in water systems, but duplex and other specialised grades are also widely applicable. Why Stainless? Stainless steel forms a self-healing passive film that protects it from corrosion in most environments without the need for coatings. This simplifies design and eliminates concerns about coating degradation, leaching, and ongoing maintenance. As a result, there’s no need to over-specify wall thicknesses to allow for corrosion loss. Its corrosion resistance ensures stainless steel piping and components retain their performance over decades, reducing both operating costs and unplanned outages. At the end of their lifecycle, these materials retain residual value and are typically fully recycled. With no internal corrosion or scaling, stainless steel preserves flow efficiency. Its strength and ductility allow for lightweight, thin-walled designs that are easier to transport and install, especially when welded or joined using loose flanges. Duplex grades enable further weight reduction in large installations like buried pipelines or bridge spans. Best Practices in Design and Fabrication For stainless steel to perform as intended, correct grade selection must be followed by attention to fabrication details. Welded joints should be prioritised to avoid crevices where corrosion could initiate. While galvanic corrosion is rare, it may occur if stainless steel is paired with less noble metals like carbon steel or galvanised iron. Proper electrical
insulation or using compatible materials is essential in such cases. Welding is the most common point of failure, but problems are avoidable with best practices: full- penetration welds, elimination of heat tint, and thorough post-weld cleaning. Contamination with iron particles can cause rust staining or pitting and should be avoided with proper material handling and workshop discipline. Case Study: Tokyo’s Long-Term Stainless Steel Strategy Tokyo once suffered massive water losses due to an ageing and fragmented infrastructure. In 1945, water loss rates exceeded 80%. While improvements brought this down to 30% by 1950, continued urban expansion kept the physical volume of lost water unsustainably high. The city responded with a systematic intervention based on three pillars:
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Issue 2 – 2025
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