| With the development and utilization of marine resources, using metal materials inseawater is becoming more and more popular. The phenomenon of corrosion willhappen where metal materials exist, hence the corrosion and protection of metalmaterials in seawater is becoming one of questions which peoples are concern with.The research of corrosion behavior of carbon steel exposed to seawater in tidalenvironments is becoming more and more meaningful. In theory, the corrosion ofsplash zone is the most serious, because the splash zone is inflatable with water,bubble and so on and is shocked by seawater waves. But in some cases, the water-linecorrosion is most serious than others, this phenomenon is called accelerated low watercorrosion(ALWC) and is often seen in many ports, especially in Europe, so study onwater-line corrosion mechanism has very important significance. The traditionalelectrochemical methods can only detect average electrochemical information on thesurface of the electrode. It is difficult to detect metal corrosion situation in electrodetiny areas, not to mention the process and mechanism of metal corrosion.This paper is to study the mechanism of carbon steel under water-line with wirebeam electrode method. It discuss factors in carbon steel corrosion behavior, forexample, the wire beam electrode＇s size, concentration of chloride ion. The details ofthe research work and the results in this paper are as follows:(1) Study on the type of11×11wire beam electrode corrosion behavior in seawater,the results show that the corrosion process of carbon steel manifest theelectrochemical inhomogeneity. The dissolved oxygen in the position of water-line issufficient so that the depolarization of oxygen as the cathode zone can occur.Theelectrode under the water line began to corrosion in the anode zone due to theinadequate oxygen. Beacuse the anode zone and cathode zone current density is different and not balance in the process of corrosion, this can result in their ownacceleration response so that it accelerate the corrosion behavior of metals.(2) Study on the type of11×11wire beam electrode corrosion behavior in0.017mol/LNaCl solution, the results show that the corrosion behavior of carbon steel material insolution is similar to the corrosion behavior in seawater, the position of liquid levelact as cathode zone and the position under the water line act as anode zone. Thecorrosion of carbon steel in0.017mol/L NaCl solution is faster and the color ofcorrosion products adhered on the surface of the electrode is not the same, the color ofcorrosion products in0.017mol/L NaCl solution is yellow, this can indicate thatchloride ion has some effect in the formation of corrosion products. The stability ofcarbon steel in0.017mol/L NaCl solution requires less time.(3) Study on the type of4×30wire beam electrode corrosion behavior in seawater, theresults show that the large size of the wire beam electrode in liquid level show thecathode current electricity and act as the cathode zone. The corrosion behavior ofelectrode under water-line about three or four line(23-26line) acting as anode is mostserious and the corrosion products in yellow attach to the electrode surface. Thecorrosion behavior of line from one to twenty-two is slower than other areas solocalized corrosion can happen. With the extension of corrosion time, the tiny zone ofelectrode above the liquid level happen to serious corrosion and generate the whitecorrosion products, some small cathode area appears from line one to twenty-two.(4) Study on the selected electrode of a column linear polarization resistance, theresults show that the resistance of single electrode from the water line to the bottomdo not show regular value. The change value of resistance of each electrode immersedin early day is apparent and stable in late period which is similar to the result of thecurrent and potential distribution. |
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