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A plain-language FAQ on Hastelloy C276: composition and UNS number, the three different temperature limits that are so often confused, welding and machining practice, hydrochloric and sulphuric acid service, NACE MR0175 sour gas limits, how C276 compares with C22 and Inconel 625, what drives the price, expected service life, and the services where C276 is the wrong choice.

This guide maps every major application by industry and by equipment type, shows which product form and ASTM specification goes with each one, and is equally explicit about the services where C276 is the wrong choice. Start at the Hastelloy C276 ultimate guide for the alloy itself.

Choosing C276 pipe comes down to five decisions in a fixed order - product specification, size and schedule, verified wall thickness, matching components and certification. Most costly mistakes are not metallurgical. They are a welded pipe supplied where seamless was required, a wall thickness that ignored the 12.5% mill tolerance, or a certificate that never arrived.

Hastelloy C276 is UNS N10276. Its internationally recognized equivalents are W.Nr. 2.4819 / NiMo16Cr15W (Germany and EN standard), NW 0276 (Japan, JIS), NS334 (China, GB/T 15008), NC17D (France, AFNOR), NCF 276 (South Korea, KS), and NiMo16Cr15W (ISO 6208). All designate the same nickel-molybdenum-chromium-tungsten alloy - provided the certificate of test matches the UNS N10276 chemistry limits.

This guide walks through every standard that applies to C276, what each one actually requires, how the ASTM documents map to their ASME counterparts, and how to use all of it when you read a mill test report or write a purchase order. For the bigger picture on the alloy itself, start with the complete Hastelloy C276 guide and what Hastelloy C276 is before diving into the standards.

Pick Hastelloy C276 when hydrochloric acid, hot chlorides, wet chlorine or mixed oxidising-reducing acids are in the stream. Pick Incoloy 825 when the duty is moderate sulfuric or phosphoric acid, sour gas inside its ISO 15156-3 envelope, or any large-tonnage job where paying two to two-and-a-half times more per kilogram buys nothing.

C276 typically costs two to three times 904L per kilogram, so the whole selection exercise is about proving that 904L cannot cover the envelope.

This guide compares them acid by acid, gives the ASME allowable stresses side by side, and shows where the 2.5-4x price gap actually buys you something.

An engineer-level comparison of Hastelloy C276 (UNS N10276) and Inconel 625 (UNS N06625): what each alloy was designed to do, where the performance envelopes genuinely overlap, and the specific conditions — reducing acids, elemental sulfur, temperature, pressure rating — that force you to one side or the other. Includes composition, PREN, mechanical and creep data, ASME code limits, NACE MR0175 / ISO 15156-3 sour-service requirements, welding consumables, ASTM product-form standards and a seven-step selection procedure.