Study On The Effect Of Conductive Polyaniline On Metal / Acid Reaction System

Conducting polymer with special structure and properties, it is widely used in the advanced industrial and technical fields. Through nearly 20 years’research, many achievements have been made in the synthesis, doping, conducting mechanism, structure, properties and application of conductive polymer materials. Different from many other conductive polymers, H+ into the main chain of the polyaniline forming radical cation, which makes polyaniline presents high conductivity. This unique doping mechanism makes doping and de-doping of the polyaniline reversible. Due to the high open circuit potential and the large charge capacity of Polyaniline, when polyaniline is connected with the metal in the proton acid, the cathode current provided by polyaniline will promote metal oxidation.Polyaniline was chemically synthesized. Factors affecting the polyaniline conductivity, including the mol ratio of oxidant to ailine monomer, reaction temperature and reaction time to the synthesized polyaniline were exmained. The synthesized conditions were optimized as follows:the solution is aniline and 2 M hydrochloric acid, the mol ratio of ammonium peroxydisulfate to anline is 1.4, the reaction temperature is 0 ℃ and the reaction time is 5 h. In this paper, the electrochemical coupling behavior of polyaniline and aluminum/nickel was studied. Some conclusions are obtained. For some metal that is easy to passivation (such as aluminum, etc.), the oxide film on the surface of the metal, which retard the active dissolution of the metal in the acid solution, was formed by the metal coupling with the polyaniline. For some metal that is difficult to passivation, (such as nickel, etc.), the galvanic effect accelerate the dissolution of metal in the acid solution. The mainly influencing factors, including acidity and temperature of the solution, were also studied. Studies show that the acidity and temperature of the solution has some effect on the dissolution rate of metals, but it can’t change the acceleration or retard dissolution of the metal by coupling.This paper investigates the polyaniline coupled with pure metal in the first. Then, the mixed metal were studied (such as stainless steel). The results show that the electrochemical coupling effect is also applicable to mixed metal. Coupling promotes stainless steel passivity, as a result, the stainless steel were protected effectively. Efficiency of anodic protection was calculated by the weights of loss. The results confirm that polyaniline can promote stainless steel passivation over a long period of time in sulfuric acid, and the efficiency of anodic protection is about 99.82%.In this paper, the conductive mechanism and doped/de-doped processes of polyaniline were discussed. Moreover, this article explores the reaction process of metal. It provides basis of theory for the electrochemical coupling effects.