| Metal corrosion induces enormous economic loss. According to the statistic figure of U.S. nation standard limit, the corrosion expense is 700 hundreds million dollar per annum, yet there are about 1/3 of which can be avoided by some knowledge and techniques. Corrosion monitoring is just one of those techniques, whose latent application is monitoring the engender and increment of corrosion. By this means, the corrosion condition can be estimated and much corrosion information can be obtained. At the same time, the needless expense of examination and maintenance can be reduced and the maintenance plan can be optimized.Up to now, corrosion monitoring techniques have been well used in such fields as cooling-water, petrochemical industry, aviation, steel-reinforced concrete, est. However, in seawater, the corrosion monitoring techniques developed relatively late and the locale ocean corrosion monitoring technique has no report till now. So it is very important to study this kind of technique.The purpose of the study is to establish one or two kinds of electrochemical monitoring techniques for the state of the metal corrosion in seawater and to normalize experiment methods and the data fitting process. Two methods of electrochemicaltechniques-weak polarization technique and galvanostatic charge technique whichcan be applied in monitoring the metal corrosion are advanced in this paper. It performs study of the feasibility of these two electrochemical techniques using for metal corrosion rronitoring in laboratory. The feasibility is studied from the view of corrosion electrochemical theory and application, mathematic model and computer program for fitting data. The study aims directly at two metal materials-T2 and Q235B which are often used in seawater. The main research contents and conclusions are described as follows:(1) The data fitting processes for weak polarization curve and galvanostatic charge curve are programmed by Qbasic language based on least square method. There's no dead circle in the process of data fitting and the electrochemical parameters are obtainedwell.(2) The two metals' steady time in seawater are obtained by recording their change curves of open circuit potential. The steady time for T2 and Q235B are 30min and 60min separately.(3) The weak polarization curves of the two metal polarization were obtained by potentiodynamical scanning measurement in sutra three-polarization system. Combining with the corrosion electrochemical parameter which obtained by strong polarization curve and making the experiment steady, the scan velocity for T2 is 0.5mV/s. The scan velocity for Q235B is 2mV/s considering the situation for change of open circuit potential and the fitting parameter at different scan velocity.(4) Continuous experiment is carried out for about one month with the natural seav\ iiter changed constantly, the weak polarization curve is measured at the same time everyday to obtain the alternation of corrosion electrochemical parameter. Meanwhile the traditional weightless experiment was carried out and the data was contrasted to the above, so the reliability that the weak polarization using for metal corrosion monitoring in seawater can be evaluated. The weak polarization results have a good coherence with the weight-ioss results.(5) The rationality and reliability of galvanostatic charge curve method, fitting process and survey system have been tested by equivalent circuit made of real resistance and capacitance elements. Anode and cathode galvanostatic charge curves for the two kinds of metal have been measured at various identical current. The numberical value of electrochemical parameters has been obtained.(6) Take the metal electrodes into still seawater for about one month, and measure the galvanostatic charge curve on schedule, the charge value of the electrochemical parameters has been obtained. The direction of change curves of the constants is consistent with the real corrosion condition of the metal in seawater.(7) The two kinds of metal...
|
PDF Full Text Request