Effect of Na_2S_2O_3 and Na_2S on the Corrosion Behavior of Q235 Steel in Sodium Aluminate Solution

摘要

Corrosion behavior of Q235 steel in sodium hydroxide solutions with S_2O_3~(2-) and different concentration of S~(2-) were investigated by immersed corrosion and electrochemical corrosion tests. Combined with polarization curve method, impedance spectrum method, SEM and EDS discussed the corrosion mechanism of Q235 steel. Results show that compared with only contains sodium thiosulfate in the sodium aluminate solution, corrosion behavior of Q235 steel soaking in the sodium thiosulfate and sodium sulfide coexisting in the sodium aluminate solution has been inhibited, S~(2-) and S_2O_3~(2-) work together to play a passive role, mainly because of S_2O_3~(2-) react with S~(2-) to generarted SO_3~(2-). Therefore, S~(2-) is thiosulfate corrosion inhibitors. With the increase of concentration of Na_2S, the corrosion rate showed a trend of first decrease and then increase, which is due to the sample surface forming loose iron sulfide corrosion products, but as a result of loose corrosion products were oxidized into dense oxide corrosion products, corrosion rate decrease.