Stabilization technology and corrosion mechanism of rust layer on Q370 weathering steel surface

摘要

A newly developed rust layer on Q370qENH weathering steel(sample C)was studied under dry–wet cycle test of 3.5 wt.%NaCl solution and salt spray test,compared with the bare weathering steel(sample A)and the weathering steel with additive contents(CuSO_(4)0.2,FeSO_(4)0.1,NaHSO_(3)0.02,NaCl 0.02,Na_(2)HPO_(4)0.01,and water balance,in mass%,termed as sample B).Corrosion mechanism of Q370qENH weathering steel after different surface treatments was investigated by means of surface potential scanning,mass change,polarization curve,and X-ray diffraction.The results of X-ray diffraction indicate that rust of bare weathering steel has rare Fe_(3)O_(4),and a dense oxide layer mainly composed of Fe_(3)O_(4) is formed on rust of both sample B and sample C.The surface potential of sample A gradually increases to−0.2 V in the dry–wet cycle test,while the surface potential of sample A maintains at about−0.6 V in the salt spray test.The surface potential of sample B and sample C is higher than that of sample A in the early stage and remains stable during the short-term accelerated corrosion test.Moreover,the mass change of sample C gradually stabilizes with time in the dry–wet cycle and salt spray test.The corrosion current of the sample A is lower than that of sample C in the initial stage of short-term accelerated corrosion test.However,the corrosion current of sample C is smaller than that of the sample A in the experiment.The main components of the deep rust of sample A areγ-FeOOH andα-FeOOH,while those of the deep rust of sample B and sample C are Fe_(3)O_(4).