Corrosion Characteristic Research Of Q235 And B480GNQR Steel In Typical Atmospheric Environment

The atmospheric corrosion of metals brings huge economic losses to the society, so it is of great significance to study the atmospheric corrosion characteristics of carbon steel which has been widely applied to the industry and weathering steel which is low cost and highly protective can be obtained from the addition of trace alloy elements.In this paper, electrochemical noise(EN) and image processing method were used to explore the corrosion behavior of Q235 carbon steel and B480 GNQR weathering steel in simulated marine atmospheric environment. The results showed that Rcd close to 2 Hz obtained by wavelet decomposition of high frequency noise data of carbon steel and weathering steel correlated well with Rn and the parameter value R by decomposing the improved images using wavelet packet-based image analysis. All parameter values showed that the corrosion rate of Q235 carbon steel and B480 GNQR weathering steel increased with the exposure time in first 24 h and the rate of B480 GNQR was lower than Q235 but both tent to be stable relatively after 24 h. R and Rcd are supposed to be effective to analysis the atmospheric corrosion damage of Q235 carbon steel and B480 GNQR weathering steel in marine environment.The wire beam electrode method(WBE) was introduced to study the influence of Cl-, SO42- and NO3- on atmospheric corrosion under thin film. The results showed that Cl- was the most aggressive to atmospheric corrosion of Q235, while SO42- was secondly and NO3- was the weakest. These three kinds of anion had different effect on protective rust layer, and Cl- could destroy destruction rust layer while NO3- had certain ability of passivation to form protective rust layer. The combination of WBE and EIS was firstly applied to study local corrosion behavior of weathering steel under marine film. The results showed that the local corrosion rate of B480 GNQR weathering steel was slower than Q235 under marine film in first 24 h. B480 GNQR weathering steel was easier to become general corrosion than Q235.