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A new super-duplex tube tailored for acids

| By Gerald Ondrey

Last month at the AMPP Annual Conference + Expo 2024 (New Orleans, La.; March 3–7), Alleima AB (Sandviken, Sweden; introduced SAF 3006 (UNS S83071), a high-alloy duplex (austenitic-ferritic) stainless steel tailored to enhance corrosion resistance in acidic and caustic environments. The new alloy is an upgrade to traditional super-duplex stainless steels. “SAF 3006 will complement SAF 2507 in dealing with corrosive conditions in heat-exchanger tubing exposed to hydrochloric, sulfuric, formic or other acids. This is our super duplex tailored to resist acids,” says Eduardo Perea, market & product manager EMEA at Alleima Tube Division. The main application is for heat exchangers in the chemical and petrochemicals industries. “Applications may include caustic evaporators, acid coolers and evaporators,” says Perea.

“Previously, most of our duplexes were developed with chloride resistance as the main focus, with high PRE (pitting resistance equivalent) levels to resist pitting and crevice corrosion. Resistance to acidic conditions was less prioritized,” explains Daniel Gullberg, manager of product development CRA (corrosion-resistant alloys). “Now, we have fine-tuned the chemical composition to resist acidic environments better. This involves a high chromium content of 30% and a molybdenum level of 3.2% to maintain good structural stability and balancing of the alloying elements,” he says

“SAF 3006 is an upgrade over existing duplex grades facing higher-than-desired corrosion rates and where extended equipment lifetime is wanted. You get all the benefits of traditional duplex steel in terms of strength, lighter weight and cost-efficiency, but tailored to resist acids. It can be used in acid-production plants with or without seawater cooling,” says Oscar Öhlin, R&D Engineer at Alleima.

Alleima will supply seamless tube and pipe in SAF 3006 in standard heat-exchanger dimensions.



Source: Alleima