What is 1.4529 Stainless Steel?

1.4529 is the EN 10088 designation for a nitrogen-alloyed, 6% molybdenum super-austenitic stainless steel, corresponding to UNS N08926 and to the steel name X1NiCrMoCuN25-20-7. It was developed for the gap between standard stainless steel and nickel-base alloys: more corrosion resistance than 316L or 904L, at lower cost than nickel alloys, in sulfuric acid, seawater and chloride-laden process environments.

Designation Note

1.4529 must not be confused with UNS N08028. The two have different compositions: N08028 carries about 27% chromium and 31% nickel with only about 3.5% molybdenum, while 1.4529 (UNS N08926) relies on 6.0-7.0% molybdenum plus nitrogen for its corrosion resistance. Orders should reference EN 1.4529 or UNS N08926 explicitly.

Chemical Composition

Composition limits below are per ASTM A240 (UNS N08926) and EN 10088-2/-3 (1.4529).

Element (wt%)	1.4529 / UNS N08926
C	≤0.020
Si	≤0.50
Mn	≤2.00
P	≤0.030
S	≤0.010
N	0.15-0.25
Cr	19.0-21.0
Ni	24.0-26.0
Mo	6.0-7.0
Cu	0.5-1.5

Mechanical Properties

Solution-annealed plate per ASTM A240: tensile strength ≥650 MPa, yield strength ≥295 MPa, elongation ≥35%, hardness ≤100 HRB. EN 10088-2 plate specifies 0.2% proof strength ≥300 MPa, tensile strength 650-850 MPa and elongation ≥35%.

Corrosion Resistance

Chloride pitting and crevice corrosion

With about 6.5% molybdenum and 0.2% nitrogen, the calculated pitting resistance equivalent, PREN = Cr + 3.3 x Mo + 16 x N, is typically 43-45, versus about 25 for 316 and about 34-36 for 904L. The grade resists pitting and crevice corrosion in seawater and chloride brines, including stagnant and fouled conditions where 316L fails rapidly.

Acid resistance

1.4529 is highly resistant to sulfuric acid over a wide range of concentrations and temperatures, and performs well in phosphoric, nitric and organic acids. Its copper content specifically improves behaviour in reducing acids such as dilute sulfuric and phosphoric acid.

Applications

Chemical processing: reactors, heat exchangers and piping for sulfuric acid service. Pollution control: scrubbers, ducts and chimney liners in flue-gas desulfurization. Offshore and marine: seawater heat exchangers, downhole tubing and wellhead components. Pharmaceutical and food: equipment exposed to aggressive cleaning media.

Welding and Fabrication

Welding should use over-alloyed nickel-base filler of the UNS N06625 class, or a matching high-alloy austenitic filler, so that the weld metal retains at least the corrosion resistance of the base material. Controlled heat input, argon shielding and post-weld cleaning restore full corrosion performance.

FAQ

1. Is 1.4529 the same as UNS N08028?

No. 1.4529 is UNS N08926 (X1NiCrMoCuN25-20-7) with 6.0-7.0% molybdenum and 0.15-0.25% nitrogen. UNS N08028 is a different composition with higher chromium and nickel and only about 3.5% molybdenum.

2. How does 1.4529 compare with 904L (1.4539)?

1.4529 has about 2% more molybdenum plus 0.15-0.25% nitrogen, lifting PREN from about 34-36 to 43-45 and giving clearly better resistance to pitting, crevice corrosion and sulfuric acid service.

3. What filler metal is used for welding 1.4529?

Over-alloyed nickel-base filler of the UNS N06625 class, or a matching high-alloy austenitic filler, to keep the weld zone as corrosion-resistant as the base metal.

4. Is 1.4529 suitable for seawater?

Yes. It is widely used for seawater heat exchangers, piping and offshore equipment, including service in chlorinated seawater and under fouling conditions.

5. In what product forms is 1.4529 available?

Plate, sheet, pipe and tube, fittings and bar, specified to EN 10088-2/-3 or ASTM A240 (plate), A312/A358 (pipe) and A182 (forgings).