Stainless Steel Grades for Tanks & Vessels: 304 vs 316, V2A, V4A & Material Numbers Explained

What Do V2A and V4A Mean – and Where Do These Terms Come From?

The abbreviations V2A and V4A originate from early experimental series in the steel industry and are not standards today but rather colloquial designations for two stainless steel groups.

The "V" stands for Versuch (experiment), the "A" for Austenit (austenite). V2A is thus the second attempt at an austenitic alloy – V4A the fourth. In daily practice, these short forms have become firmly established, even though they no longer appear in any current standard.

• V2A encompasses chromium-nickel steels, primarily grade 1.4301 (AISI 304).
• V4A additionally contains approximately 2% molybdenum and includes grades such as 1.4401 (AISI 316) and 1.4404 (AISI 316L).

In terms of standards, the correct designations are material numbers according to DIN EN or AISI numbers. In practice, however, V2A and V4A appear in virtually every enquiry and quotation.

How to Read a Stainless Steel Material Number (1.4301, 1.4404 & Co.)

Every stainless steel material number follows a fixed system. Once you understand it, you can immediately classify any grade.

Using 1.4301 as an example:

• 1 — Main material group: steel and cast steel
• 43 — Grade class: corrosion-resistant steels (chromium-nickel alloys)
• 01 — Sequential number: distinguishes materials within the same group

All stainless steel material numbers in vessel construction start with 1.4... – the last two digits differentiate the exact alloy variant. For daily work, it is important to know: 1.4301 and 1.4307 are both V2A steels, 1.4401 and 1.4404 are both V4A – each with minor differences in carbon content and corrosion resistance.

V2A vs V4A: What Is the Key Difference?

The key difference lies in the molybdenum content: V4A contains approximately 2% additional molybdenum, which significantly increases corrosion resistance – particularly against chlorides.

For stainless steel vessels and tanks in the food, pharmaceutical or chemical sectors, V4A is the standard choice for all product-contact surfaces. V2A is suitable for structural, non-media-contact elements such as frames or support legs – saving material costs without compromising product safety.

• V2A (1.4301): Good corrosion resistance, widely used across industries, economical.
• V4A (1.4404): Enhanced resistance to chlorides, saltwater and sulphuric acid. Standard for product-contact components.
• Rule of thumb: Wherever the medium is aggressive, salty, acidic or pharma-cleaned, V4A is the right choice.

Stainless Steel Grades Compared: 1.4301, 1.4404, 1.4571 and More

Direct comparisons between individual grades are particularly frequently requested. The following tables show the most important representatives of both groups at a glance.

V4A group grades

V4A is the upgraded version of V2A: the addition of molybdenum significantly increases corrosion resistance, especially against chlorides and sulphuric acid. Heat resistance is also higher than with V2A.

Key comparisons in detail

1.4404 vs. 1.4401: Both belong to the V4A group and are almost identical in practice. The difference lies in the carbon content: 1.4404 (AISI 316L) has a lower C content, making it more weldable and marginally more resistant to intergranular corrosion. In most vessel construction applications, both are fully interchangeable.

1.4571 vs. 1.4404: 1.4571 (AISI 316Ti) additionally contains titanium as a stabiliser. This makes it particularly suited for high-temperature applications above 350 °C. Its corrosion resistance matches that of 1.4401/1.4404. Disadvantage: titanium prevents uniform surface finishing – if you want to polish your vessel to a mirror finish, 1.4571 should be avoided.

1.4541 – V2A or V4A? This question comes up regularly: 1.4541 (AISI 321) is a V2A steel that has been stabilised with a titanium addition. It offers better corrosion resistance than the standard V2A (1.4301) but is not suited for pharmaceutical applications requiring mirror-polished surfaces.

V2A group grades

V2A encompasses all chromium-nickel steels without molybdenum addition. By far the most common representative is 1.4301 – it accounts for over 50% of the total market.

V2A is used across all industries: in food processing, the chemical and pharmaceutical industries, construction and automotive manufacturing. The choice of grade within the V2A group depends on the specific requirements for weldability, temperature resistance and surface quality.

Special Alloys for Extreme Conditions – When Are They Worth It?

For particularly aggressive media, even V4A reaches its limits. In such cases, special alloys with significantly higher alloying content are used.

• 1.4529 (Alloy 926): With 6.5% molybdenum, this material offers excellent protection against pitting and crevice corrosion – even at higher chloride concentrations, such as those found in marine chemistry or salt processing.
• Hastelloy: A brand name for highly alloyed nickel-molybdenum alloys with up to 30% molybdenum. Resistant even to concentrated hydrochloric or sulphuric acids – albeit at a significantly higher material cost.

The decision in favour of a special alloy should always be based on a media analysis and operating temperature assessment. In many cases, selective use of V4A for product-contact components is the more economical solution – with special alloys only where they are technically essential.

Corrosion Resistance Overview: Which Grade for Which Medium?

Corrosion resistance is the decisive selection criterion for stainless steel grades in vessel construction. Correct matching of medium and material prevents costly damage and downtime.

• Water, food products, weak acids: V2A (1.4301) is sufficient.
• Salt-containing media, chlorides, whey, brine: V4A (1.4404) is mandatory.
• Sulphuric acid, nitric acid, phosphoric acid: V4A (1.4404 / 1.4435) recommended, depending on concentration and temperature.
• Concentrated hydrochloric acid, highly corrosive acids: Special alloys such as 1.4529 or Hastelloy.