含SO 2 大气中20碳钢腐蚀产物的演变
摘要
The evolution of corrosion products of 20 carbon steel in simulated humidity atmo- sphere containing SO2 was investigated by means of OM, SEM, XRD and localized electrochemical impedance spectrum (LEIS). Results showed ferrous hydroxide film firstly formed on the sample sur- face; the film ruptured in the acidic medium, and then filaments with green heads occurred. The filaments grew along the grain boundaries and into ferrite grain. Ferrite phase was dissolved when SO2 ,O 2 and H2O continuously penetrated into the ruptured ferrous hydroxide film and sulphate nests formed. Inside the nests FeSO4 reacted with O2 and H2O to form FeOOH, finally the cellular corro- sion products formed. The cellular corrosion products and its impedance increased, and the rust layer became even and compact with further corrosion. Cellular products grew faster with the increasing SO2 concentration.