| The corrosion and protection of metals has become one of the most serious problems which has to face up with during the construction of industrial modernization.Financial loss caused by metallic corrosion in developed centuries has reached up to700 billion dollars every year, which occupied 2~4% of Gross National Product(GNP)and has been six times of that caused by natural disasters, such as earthquake,flood,hurricane and so on. The annual financial loss caused by metallic corrosion in our country is at least 20 billion RMB. So the corrosion of metals has become a major challenge for our country to move forward on the road of industrialization. Most of the anticorrosion pigments used in the anticorrosion coatings contain zinc, chromium, lead and other heavy metal compounds, which have great risks to the environment.Therefore, it has become a hot research topic to study the new anticorrosion coating.As a new kind of functional polymer material, polyaniline(PAn) has attracted much attention among researchers in the world due to its simple synthesis, particular doping-dedoping mechanism, good redox property and environmental stability, high electrical conductivity, as well as distinctive electrical, optical and magnetic properties.However, the big rigid of its chain backbone and strong intermolecular interaction restrict its solubility and melt, which further hinder its applications in many fields.Since in 1985, Deberry reported firstly that conducting polymer can offer corrosion protection, conducting polymer has been extensively researched on corrosion protection, and now some paint coating containing conducting polymers have been developed. Although many researchers found that conducting polymers can reduce thecorrosion rate of metal,but some researchers have different views.Because of the conductive polymer preparation, doping, research methods, as well as the different corrosive media, the results are inconsistent. Yet the mechanistic of corrosion protection of conducting polymers has not been reported exactly.Polyaniliane is selected for their usage in this paper. Firstly, the effects of polymer coating on metal corrosion under different pH and curing agent were studied.Polyaniline was synthesized by in situ polymerization in epoxy resin. By electrochemical methods, it is found that the polyaniline synthesized under the condition of pH=1.0 had better corrosion protection performance on the A45 steel in3.5 wt% NaCl solution. The use of 593 type curing agent of polyaniline film of anticorrosion ability is better than the T31 and polyamide 650; oxidation potential of high conductive polymer on metal corrosion protection performance is excellent.Secondly, the effect of different dosage of organic modified attapulgite(OAT) on the corrosion protection of polyaniline coating was explored. In this paper, the corrosion resistance of polyaniline film doped with different OAT was tested by electrochemical method and salt spray test. Electrochemical corrosion testing methods found in 3.5 wt% NaCl solution with the increase of dosage of OAT the corrosion potential showed first increased and then decreased; when the dosage of OAT by 1 wt%,the corrosion potential of the polyaniline anticorrosive coating reached-0.365 V, which had the best anticorrosion performance. Adhesion tests show that, in the case of less OAT content, polyaniline anticorrosion coating has good adhesion to the substrate.Thirdly, the influence of different preparation methods on the corrosion protection properties of polyaniline coating was studied. Polyaniline anticorrosive coatings were prepared by two different synthetic environments. Adhesion tests show that the use of one step preparation of Polyaniline/organic modified attapulgite coating has better adhesion level; electrochemical corrosion test results show that in 3.5 wt% NaCl solution, the one step preparation of Polyaniline/organic modified attapulgite coating on the A45 steel has better corrosion protection performance and potential has a positive shift of 0.09 V compared to another method.Finally, this paper uses the method of mathematical modeling, with the help of MATLAB software to simulate the effect of polyaniline morphology and corrosionprotection. The results showed that polyaniline powder obtained in this study are in micron level, in this range, unshaped, spherical polyaniline powder decreases with increasing particle size, anticorrosion properties increase, the degree of fitting reaches more than 99%; fibrous polyaniline powder fitting degree is 76.28%. The analysis of the experimental data showed that amorphous polyaniline in nano scale can reach the highest corrosion potential for-0.3233 V; fibrous polyaniline in nano scale can reach the highest corrosion potential for-0.3894 V; spherical polyaniline in nano scale the highest corrosion potential for-0.1859 V. |
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