Corrosion of materials for apparatus used in the production of organic synthetic dyes

Conclusions

• 1. The weld seams of 1Kh18N9T, Kh18N12M2T, Kh18N12M3T steels have a biphase austenitic-ferrite structure and are subject to selective corrosion around the \gd-ferrite in media used for the production of maleic anhydride. The weld seams of OKh23N28M3D3T steel have a purely austenitic structure and are subject to very slight general corrosion in this medium.

• 2. OKh21N5T steel and weld seams in this steel undergo insignificant general corrosion in media used for wet recovery of waste gases in the production of phthalic anhydride, but separate deep corrosion pits occur in the weld seam metal. Shallow pitting corrosion occurs in welded 1Kh18N9T steel.

  Stainless steels containing molybdenum (Kh18N12M2T and OKh21N6M2T) and their weld seams are subject neither to general nor to pitting corrosion.

• 3. Technically pure VT1-1 titanium is corrosion resistant in media used for the production of isatin by precipitation with hydrochloric acid. When isatin is precipitated with sulfuric acid then OKh23N28M3D3T steel should be used.

• 4. Weld seams of Kh18N12M2T and OKh21N6M2T steels have a biphase structure (\gg+\gd); they undergo accelerated corrosion in the austenite matrix in the media used for the production of 3-amine-5-sulfosalicilic acid.

• 5. OKh23N28M3D3T steel with residual stresses induced by forming, welding, and other technological processes undergoes transcrystalline corrosion cracking in media used for the production of benzanthrone.

This steel can be used if the finished machine parts can be annealed at 950°C for 1 h and cooled in air to relieve internal residual stresses.