Material selection by service

This is a starting point; final selection depends on concentration, temperature, impurities and design code.

316L urea grade

Urea plants operate with ammonium carbamate solutions at high pressure and temperature, which attack ordinary stainless steel. SS 316L pipes in a special urea grade – with higher minimum molybdenum and nickel, very low ferrite and controlled impurities, and tested for corrosion resistance with the Huey (boiling nitric acid) test – are used for many parts of the synthesis loop. More resistant austenitic 25-22-2 steels and duplex steels are used for the most severe sections such as strippers. Urea-grade requirements are set by the process licensor, so please send the licensor's material specification with the enquiry.

Acids – Alloy 20, 904L and Hastelloy

For sulphuric acid, Alloy 20 pipes and tubes and SS 904L give low corrosion rates across a wide range of concentrations, with Incoloy 825 as an alternative. For hot, concentrated or contaminated acids, hydrochloric acid and mixed acids, Hastelloy pipes and tubes in C276 or C22 are used. Phosphoric acid plants use 904L, Alloy 20 and high-alloy nickel alloys depending on the chloride and fluoride content of the phosphate rock.

Chlorides and cooling water

Chemical plants often use brackish or seawater cooling and handle chloride-contaminated process streams, which cause pitting and stress corrosion cracking in 304L and 316L. Duplex steel pipes and tubes, SMO 254 pipes and tubes and titanium pipes and tubes are used for heat exchangers and piping in this service. Titanium is the standard material for wet chlorine and chlorine dioxide.

Fertiliser plants

Fertiliser complexes combine ammonia, urea, nitric acid, ammonium nitrate, phosphoric acid and sulphuric acid units, so a single site may need carbon steel, low-temperature steel, several stainless grades and nickel alloys. Ammonia synthesis loops use chrome-moly and carbon steel suited to hydrogen service; nitric acid plants use 304L and nitric-grade stainless; sulphuric acid plants use Alloy 20 and high-silicon stainless steels for acid coolers and piping; and phosphoric acid plants use 904L and nickel alloys. We supply material for new units, expansions and shutdowns across these services.

Products for chemical plants

We supply seamless pipes and tubes, welded pipes and tubes, flanges, pipe fittings, plates, sheets, round bars and fasteners in all these materials, together with stub ends and lap joint flanges for economical alloy piping, and PTFE-compatible flange facings. Material is supplied with mill test certificates, with intergranular corrosion tests, ferrite measurement, PMI and third-party inspection on request. All industries we serve are on the industries page.