The truth behind valve corrosion in chlorine and hydrochloric acid, and the solution using tantalum alloys

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In industries such as chemical processing, chlor-alkali, and pharmaceuticals, valves are constantly subjected to the dual “attack” of chlorine gas (dry/wet chlorine) and hydrochloric acid (HCl solution). Traditional stainless steel (such as 316L) or Hastelloy valves may seem durable, but they often develop pitting, stress corrosion cracking (SCC), hydrogen embrittlement, or uniform thinning within a few months, leading to leaks, production shutdowns, and even safety accidents. https://p3-sign.toutiaoimg.com/tos-cn-i-axegupay5k/dfed348ec7834c6ba8a0910efd8b737b~tplv-tt-origin-web:gif.jpeg?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1773980235&x-signature=4uBQNFlCZLmLBZBGD9%2FgvMGd3q8%3D The true mechanism of valve corrosion in an environment of chlorine gas and hydrochloric acid: dry chlorine gas vs. wet chlorine gas. Dry chlorine gas (with 149°C moisture content) can easily cause chloro-iron fires (posing a fire risk to carbon steel). Wet chlorine or chlorine containing water: It produces hydrochloric acid and hypochlorous acid, which destroy the metal’s passivation layer and cause severe corrosion. Stainless steel (316L): Chloride-induced pitting and chloride stress corrosion cracking (SCC), especially in high-stress areas such as welds and fasteners. Hastelloy C-276: May still experience localized failure under high chloride levels and high temperatures. Titanium alloy: Burns easily in dry chlorine gas (> -18°C); corrosion intensifies in cracks when exposed to wet chlorine gas. Typical valve failures: Micro-cracks or perforations occur in the valve stem, valve seat, and sealing surfaces, resulting in a significant increase in the risk of leakage. Hydrochloric acid (HCl solution) is a strongly reducing acid; almost all metals, including stainless steel, are not resistant to it. concentration