Why is 444 used for water tanks instead of 316L?

Its ferritic structure cannot suffer chloride stress-corrosion cracking, a common failure of austenitic tanks in hot chlorinated water, and its pitting resistance is similar to 316L.

Grades · Stainless Steel · 444

444

Data verified

444 is a stabilised, molybdenum-bearing super-ferritic stainless whose pitting resistance rivals 316L while being immune to chloride stress-corrosion cracking. It is widely used for solar and electric water-heater tanks and heat exchangers.

Hardness≤217 HB (annealed)

DIN1.4521

AISI444

JISSUS444

CategoryStainless Steel

Chemical composition

Element	Content (%)
C	≤0.025
Si	≤1.00
Mn	≤1.00
P	≤0.040
S	≤0.030
Cr	17.50–19.50
Ni	≤1.00
Mo	1.75–2.50
Ti+Nb	0.20+4×(C+N)–0.80
N	≤0.035

Weight percent, per the governing standard ranges. Actual values per heat are on the mill certificate.

Properties

Delivery condition	Annealed
Hardness	≤217 HB (annealed)
Tensile strength	415–640 MPa
Density	7.70 g/cm³
Magnetic	Yes
PREN	~24 (comparable to 316L)

Heat treatment

Anneal 840–900 °C, rapid cool preferred to avoid embrittling phases.

Equivalent grades

Standard	Designation
din	1.4521
aisi	444
jis	SUS444

Compare side by side: 444 vs 439 · 444 vs 436

Equivalents overlap in chemistry and use but are not always identical — see our equivalents guide before substituting in certified designs.

Applications & Processing

Applications: Water-heater and solar tanks, heat-exchanger tubing, food processing equipment, chimney liners.

Processing: Weldable in thin gauges with care over heat input; lower toughness than austenitics limits heavy fabrication; excellent for tube and tank work.

FAQ

Why is 444 used for water tanks instead of 316L?: Its ferritic structure cannot suffer chloride stress-corrosion cracking, a common failure of austenitic tanks in hot chlorinated water, and its pitting resistance is similar to 316L.

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Source: ASTM A240 / EN 10088 published ranges · Last updated 2026-11-03. Data is indicative — verify critical values against the governing standard and mill certificate before use.