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As one of the most prevalent and widely utilized grades in austenitic stainless steels, 304 stainless steel (UNS S30400) finds extensive applications in construction, food processing, medical, chemical, and household appliance industries. Its popularity stems from excellent corrosion resistance, favorable formability, and reliable weldability. However, 304 stainless steel is not “all-purpose”—its performance varies significantly across different service environments. This paper systematically analyzes the performance of 304 stainless steel plates under five typical conditions: atmospheric, fresh water, seawater/high-chloride, acid-alkali, and high-temperature environments. 1. Performance in Atmospheric Environments In ambient atmospheres of ordinary urban or rural areas, 304 stainless steel plates demonstrate outstanding corrosion resistance. A dense chromium oxide passivation film (Cr₂O₃) spontaneously forms on the surface, effectively isolating oxygen and moisture to prevent further oxidation of the substrate. Consequently, in dry, clean, and industrially unpolluted air, 304 stainless steel exhibits negligible rusting and maintains a bright, as-new appearance over extended periods. The scenario differs notably in industrial zones or coastal regions, however. Industrial atmospheres typically contain pollutants such as sulfur dioxide (SO₂) and nitrogen oxides, which dissolve in water to form acidic media that can degrade the passivation film. Coastal atmospheres, on the other hand, contain high levels of sodium chloride particles—chloride ions possess strong penetrability, readily inducing pitting corrosion. Despite these challenges, 304 stainless steel still maintains satisfactory performance in most mild industrial or marine atmospheres, with a service life exceeding 10 years. For long-term exposure to harsh marine environments characterized by high salt spray and high humidity (e.g., offshore platforms, ship decks), localized rust spots may occur. In such cases, upgrading to higher-grade 316 stainless steel is recommended. 2. Performance in Fresh Water Environments 304 stainless steel plates deliver stable performance in fresh water environments, including tap water, river water, and lake water. Fresh water typically has a chloride ion concentration below 200 ppm and a near-neutral pH value, conditions under which the passivation film of 304 stainless steel remains intact. This stability makes it a preferred choice for drinking water piping systems, hot water storage tanks, and water treatment equipment. Notably, pitting or crevice corrosion may still occur if the water contains elevated chloride levels (e.g., certain groundwater sources or chlorine-disinfected municipal water supplies), especially under elevated temperatures (>60°C) or stagnant flow conditions. For instance, in hot water circulation systems with high water hardness and excessive chlorine content, micro-corrosion pits may develop on the inner wall of 304 stainless steel pipes. Therefore, risk assessment based on water quality reports is essential during design. Cathodic protection measures or material upgrading to 316L stainless steel should be implemented when necessary. 3. Performance in Seawater and High-Chloride Environments This represents a critical limitation of 304 stainless steel. Seawater contains chloride ions at concentrations exceeding 19,000 ppm—far beyond the tolerance threshold of 304 stainless steel (generally recognized as 200–500 ppm). In such environments, 304 stainless steel is highly susceptible to pitting corrosion, crevice corrosion, and even stress corrosion cracking (SCC). Experimental data indicates that visible pitting can be observed on 304 stainless steel surfaces after several weeks of immersion in room-temperature seawater. When combined with tensile stress (e.g., welding residual stress or mechanical loads), catastrophic stress corrosion cracking may occur at temperatures above 60°C. For this reason, 304 stainless steel is not recommended for structural components in direct contact with seawater, such as ship hulls, seawater desalination units, and offshore platform support structures. In these applications, molybdenum-containing 316 stainless steel, 2205 duplex stainless steel, or super austenitic stainless steels (e.g., 904L, 6% Mo alloys) are preferred alternatives. 4. Performance in Acid-Alkali Environments 304 stainless steel exhibits moderate tolerance in weak acid and weak alkali environments but performs poorly under strong acid or strong alkali conditions. Specific performance characteristics are as follows: – Nitric acid environment: 304 stainless steel demonstrates excellent corrosion resistance to nitric acid with concentrations ≤ 65%, making it suitable for nitric acid storage tanks and piping systems. – Organic acids (e.g., acetic acid, citric acid): At room temperature, it maintains good corrosion resistance, hence its widespread use in the food and pharmaceutical industries. – Hydrochloric acid and sulfuric acid: Even low-concentration hydrochloric acid or dilute sulfuric acid rapidly corrodes 304 stainless steel, as stable passivation film formation is inhibited. Consequently, its use in hydrochloric acid storage or transportation systems is strictly prohibited. – Alkaline environment: 304 stainless steel performs adequately in alkali solutions (e.g., sodium hydroxide) at room to medium concentrations. However, alkali embrittlement may occur in high-temperature, concentrated alkali solutions. In summary, 304 stainless steel is suitable for neutral or weakly corrosive media with a pH range of 4–10. Beyond this range, thorough risk assessment or material substitution is required. 5. Performance in High-Temperature Environments 304 stainless steel maintains oxidation resistance at temperatures up to 870°C (intermittent service) or 925°C (continuous service). It retains good strength and oxidation resistance at high temperatures, making it suitable for stoves, exhaust pipes, heat exchangers, and similar equipment. A critical concern is the “sensitization” phenomenon that occurs during prolonged service at 450–850°C. At this temperature range, carbon tends to combine with chromium to form chromium carbide (Cr₂₃C₆), leading to chromium depletion along grain boundaries and subsequent corrosion resistance degradation. This issue is particularly pronounced in welding heat-affected zones, where intergranular corrosion may occur. To mitigate this risk, the low-carbon variant 304L (carbon content ≤ 0.03%) can be adopted, or solution heat treatment can be performed to restore corrosion resistance. Additionally, 304 stainless steel may undergo sulfidation corrosion in high-temperature sulfur-containing atmospheres (e.g., combustion exhaust gases). In such cases, higher-alloyed materials should be considered. #304stainlesssteelplates #qualityguarantee #stainlesssteel #304