At Anzor, we supply some of the world’s most advanced stainless steels. These grades are engineered for superior strength, corrosion resistance, and long-term performance in the toughest environments — from marine to coastal construction and aerospace applications.  When a Stainless Steel Grade has a Pitting Resistance Equivalent Number (PREN) over 40, it is a 'SUPER' grade and should be fully resistant to localised corrosion (pitting/crevice corrosion) when immersed in seawater.  These grades are not only 'SUPER' in terms of corrosion resistance, but many Anzor stock are also 'SUPER' in terms of strength and ductility (see Bumax DX129)

The 5 Stainless Families

There are five families of stainless steel because their microstructures—austenitic, ferritic, martensitic, duplex, and precipitation hardening—are formed by different combinations of alloying elements like chromium, nickel, and molybdenum. Each structure gives unique balances of strength, corrosion resistance, and formability, making them suited to different environments and uses. This classification helps engineers and fabricators select the right stainless steel for performance and cost.

What defines 'SUPER'?

If the Pitting Resistance Equivalent Number (PREN) for a stainless steel grade is greater than 40, it will be resistant to localised corrosion (Pitting/Crevice Corrosion) when immersed in seawater and it is considered 'SUPER'.

*Stainless Steel Grade 1.4529 - meeting the EU Standard (EN 13451) for use above indoor swimming pools and DIN EN 1993-1-4:2015-10 / Eurocode 3 – Annex C: Corrosion Resistance Classes (CRC I–V) for use in tunnels.

Indoor Swimming Pools are very different from outdoor swimming pools, and even seawater – they are one of the most corrosive environments to be found. It is not being in contact with the pool water that is an issue, but rather the atmosphere above it. Raised temperature, high humidity and chemicals in an aerosol form – especially Chlorine compounds.

In this environment, grades of stainless steel like 304, 316 and even 2205 can suffer Stress Corrosion Cracking (which is hard to detect), especially when these components are under load.

A fatal pool roof collapse in the early 1990s in Europe was due to stress corrosion cracking of 304 roof supports.  Then after testing, the report suggested that 6% Mo alloys would NOT crack and subsequently the EU standard EN 13451 was created, which calls for stainless steel grades such as 1.4529 being used above indoor swimming pools for load bearing, safety critical components which are not regularly cleaned and exposed to indoor swimming pool environment.

Click here to check CRC - Corrosion Resistance Classes

Comparison Chart

Why Go Stronger? So, You Can Go Smaller.

See full Tensile Strength Comparison Chart

BUMAX® DX 129's core is its duplex stainless steel (2205, EN 1.4462)—a balanced austenitic-ferritic microstructure with ~50/50 ferrite and austenite phases. It is a premium alloy superior to 316 SS, and contains 22% chromium, 5% nickel, 3.2% molybdenum, and 0.18% nitrogen for optimized mechanical performance.

Super Strength Metrics

BUMAX® DX 129 matches the tensile power of class 12.9 carbon steel fasteners while outperforming in real-world durability. Key metrics include:

• Tensile Strength: Minimum 1,200 MPa
• Yield Strength: Minimum 1,080 MPa
• Elongation: At least 0.4 times the nominal diameter—33% better ductility than brittle carbon steel equivalents, allowing it to flex under overload without fracturing.
• Superior Corrosion Resistance: PREN > 34 (compared to 316 which has PREN ~24)
• Fatigue Resistance: Superior to both 316 stainless and 12.9 carbon steel

Corrosion Resistance - PREN Values

Tensile Strength Comparison Chart

Stainless Steel Grades

NB:This information is provided as a guide only. Anzor does not accept liability for the application of this information.

For technical advice about stainless steel and grade selection, you can log a free enquiry with the Nickel Institute.