Stainless steel is known for its strength and resistance – but not all stainless steel grades are equal. When the material is exposed to extreme environments such as high temperatures, salt water, or chemicals, special requirements are placed on the choice of steel grade. Here, we clarify what happens and when it is worth choosing a higher grade.
High temperatures – how much can stainless steel withstand?
At high temperatures, even stainless steel can be affected.
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A2 (304) can withstand temperatures up to approx. 600 °C before its strength decreases significantly.
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A4 (316) has similar heat resistance, but slightly better stability thanks to its molybdenum content.
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Special alloys such as heat-resistant steels (e.g., 310 or 321) are used in furnaces, engines, and industries where the temperature regularly reaches over 800–1000 °C.
Standard screws in A2 or A4 are not intended for constantly high temperatures – choose special steel if the environment is extremely hot.
Salt water and marine environments
Salt water is one of the most demanding environments for metals.
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A2 (304) works in normal outdoor environments but is sensitive to pitting corrosion in salt and chlorides.
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A4 (316) is the obvious choice near the ocean, piers, or in pool environments – the molybdenum makes it significantly more resistant to chloride attacks.
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Duplex and super duplex steels are used offshore and on ships, where corrosion attacks are the toughest.
Chemicals and industrial environments
Many chemicals can attack even stainless steel.
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A2 should be avoided in highly acidic or chloride-containing environments.
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A4 is more resistant, but not completely immune to strong acids or bases.
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Special alloys such as Hastelloy or acid-resistant duplex steels are used in process industries, paper mills, and chemical handling.
Here, it is important to always match the steel grade to the specific chemical – the wrong choice can quickly lead to costly corrosion.
When are special alloys required?
It can be worth moving up a level from standard A2 or A4 when:
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The temperature is very high (over 600 °C).
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The environment is highly chloride-containing (salt water, chlorine pools).
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Exposure occurs to aggressive acids, solvents, or bases.
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Requirements for longevity and safety are extra high (industry, offshore, medical equipment).
Summary
Stainless steel is a fantastic material, but the choice of steel grade is crucial in extreme environments.
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A2 is sufficient for most everyday environments.
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A4 is standard for marine and more demanding conditions.
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Special alloys are required for very high temperatures, long-term salt water exposure, or aggressive chemicals.
Choosing correctly from the start saves time, money, and trouble – and allows stainless steel to truly live up to its reputation as “almost indestructible”.