Corrosion resistance and electrochemical behavior of building materials in the regeneration of nitric acid

Abstract

Repeated quenching of steel 08KhiSGSN2T (see Table 2) from l000~ did not eliminate the tendency to intercrystalline corrosion~ Repeated quenching of the specimen of steel of the same melt from 1200~ and subsequent inductive heating at 550~ did not cause intercrystalline-corrosion tendency. This was apparently because after quenching from 1200~ the structure of this steel contained a predominant ferrite component, For steel 08Kh22N6T, intercrystalline-corrosion tendency was observed only after quenching from I050~ and an increase in the time of inductive heating at 550~ to 8 h~ Intercrystalline-corrosion tendency was not detected on specimens of steel 08Kh21N6M2ToBending of the specimens to 30 ~ on a mandrel with a radius equal to twice the thickhess of the specimen caused strain of the outer fiber of the specimen of not more than 5% and, therefore, could not be the cause of crack formation in the absence of intercl~stalline corrosion. An increase in the boiling time of two-phase steels in tests by the ~U method to 56 h should not be considered as a significant increase in the severity of the test conditions in comparison with the conditions recommended by GOST 6032-75 because even during boiling for 56 h and bending of the specimens to 30 ~ , the depth of corrosion in meta!lographic investigation was 5-10 ~m, something which corresponded to low intensity of intercrystalline corrosion determined by a standard method.