Why is Alloy 625 the most cited grade in this family?

Because it combines good mechanical strength, excellent resistance to severe chlorides and reasonable weldability for a nickel alloy — a versatile compromise that makes it the most common starting point.

What's the difference between Alloy 600 and Alloy 800?

Alloy 600 is a nickel-dominant nickel-chromium alloy, for high temperature and oxidation resistance. Alloy 800 (and its H/HT variants) is an iron-nickel-chromium alloy, halfway between stainless steel and pure nickel alloys — less costly, for less severe conditions.

Is C-276 really necessary for my application?

C-276 is reserved for some of the most severe acidic and chlorinated environments. If your environment is less aggressive, Alloy 625 or even a super austenitic grade may be sufficient at a lower cost — a case-by-case review remains necessary.

Are these grades available in full piping, not just tube?

Yes, depending on grade and mill — tubes, fittings, flanges and bars are possible. Send us your requirement via a quote request for a precise confirmation.

GRADE FAMILY

Nickel alloys

Nickel alloys take over when even a super austenitic grade is no longer enough: very high temperature, severe chlorides, or aggressive acidic environments outside the domain of stainless steel. Alloy 625 is the most versatile reference; 600, 800, 825 and C-276 cover more specific cases.

What is a nickel alloy?

A nickel alloy is a metal where nickel is the base element rather than a mere addition as in stainless steel. This nickel base, combined with chromium and sometimes molybdenum, extends the domain of corrosion and temperature resistance well beyond what stainless steels, even super austenitic ones, can offer.

When to choose this family — and when not to?

Choose it when the environment exceeds the domain of stainless steel: very high continuous temperature, severe chlorides combined with acidity, or steam generators and heat exchangers under extreme conditions. Avoid it for routine use: the cost of these alloys is only justified when stainless steel, super austenitic included, genuinely reaches its limits.

Grades in this family

The grades listed are examples, never a closed catalogue — every grade belongs to one of the nine families, which is what makes this claim reliable.

Examples in the nickel alloys family — EN and PREN filled in where available, not a closed catalogue
Grade (example)	EN	Indicative PREN
600	2.4816	14–17 †
625	2.4856	50–54 ¹
800/H/HT	1.4876	19–23 †
825	2.4858	28–35 †
C-276	2.4819	75 (PREW) †

† PREN is calculable but not the deciding factor for this grade, see the note below · ¹ usual value from the technical literature, not drawn from a product standard.

PREN caveats (†)

600: ⚠️ A misleading indicator on this alloy. Its PREN of 14 to 17 is still lower than a 304L's, yet Alloy 600's performance comes from its 72% nickel content: resistance to chloride stress corrosion cracking, high-purity water and caustic environments.
800/H/HT: ⚠️ Not relevant: Alloy 800 is chosen for hot oxidation, carburisation and nitriding resistance, not aqueous corrosion.
825: Indicative only. On an alloy with 38–46% nickel, performance isn't captured by PREN alone: nickel provides resistance to chloride stress corrosion cracking, and the molybdenum-copper pair provides resistance in reducing environments.
C-276: Tungsten requires the PREW formula, not PREN₁₆. For reference: 2507 at 42–43, 254 SMO at 43–45.

Typical applications for this family: High temperature · Severe chlorides · Steam generators and heat exchangers.

My grade isn't listed →

Available forms and dimensions

Tubes, fittings, flanges and bars are possible depending on grade and mill, but availability and lead times vary more than with standard stainless steel. Outer diameter from 10 to 219 mm — structured data available for 625 only. The other grades in this family don't yet have this in our structured reference data: send us your requirement via a quote request.

Applicable standards

ASTM B163
ASTM B407
ASTM B444
ASTM B622
ASME SB163
ASME SB407
EN 10216-5
DIN 17751

Frequently asked questions

Why is Alloy 625 the most cited grade in this family?: Because it combines good mechanical strength, excellent resistance to severe chlorides and reasonable weldability for a nickel alloy — a versatile compromise that makes it the most common starting point.
What's the difference between Alloy 600 and Alloy 800?: Alloy 600 is a nickel-dominant nickel-chromium alloy, for high temperature and oxidation resistance. Alloy 800 (and its H/HT variants) is an iron-nickel-chromium alloy, halfway between stainless steel and pure nickel alloys — less costly, for less severe conditions.
Is C-276 really necessary for my application?: C-276 is reserved for some of the most severe acidic and chlorinated environments. If your environment is less aggressive, Alloy 625 or even a super austenitic grade may be sufficient at a lower cost — a case-by-case review remains necessary.
Are these grades available in full piping, not just tube?: Yes, depending on grade and mill — tubes, fittings, flanges and bars are possible. Send us your requirement via a quote request for a precise confirmation.