The Effect Of Polyaniline To Galvanic Anodic Protection On Ferrous Metals

Corrosion is the destructive result of chemical or electrochemical reaction between a metal or metal alloy and its environment, which is a common phenomenon. It occurs in all over the fields in national economy. Where metal or metal alloy is used, corrosion exists absolutely to some extent. It is aware that corrosion has consumed enormous economic cost, brought many disastrous accidents, exhausted the precious resource, contaminated the environment and even prevented the development of high-tech. It is always our aim to find a cheap, effective and secure measure to prevent corrosion. Since Deberry first found the anticorrosion character of polyaniline (short for PANI), PANI has become an important material to prevent corrosion by the means of coating on the surface of metals as followed: depositing directly, dissolving and coating, coating as paint. But the application of all these methods is restricted because of their fatal shortcomings.In this work, we first suggest and study a new anodic protection method called Galvanic Anodic Protection to protect ferrous metals. The results are as follows:(1) PANI was chemically synthesized. The influencing factors, including the kind and concentration of the acid in the synthesized solution, the mol ratio of oxidant to aniline monomer, reaction temperature and reaction time to the synthesized PANI, were examined. The synthesized conditions were optimized as follows: the solution is 0.5M aniline and 2M HClO4, the mol ratio of (NH₄)2S2O8 to aniline is 1:1, the reaction temperature is about 0℃, and the reaction time is 6h.(2) The separate PANI powder electrode has been made by a new and easy method, and its mechanical intensity is very good. It was proved that the PANI powder electrode had good electrochemical properties and could provide initial current and steady current by potentiodynamic polarization and potentiostat polarization.(3) Coupling the PANI powder electrode with lCrl3, the Galvanic Anodic Protection of PANI to stainless steel was studied and the major influencing factors such as theratio of PANI to lCrl3, the concentration of the acid, the temperature and the kind of acid were investigated. The results show that the PANI powder electrode can protect lCrl3 from corrosion in many experimental conditions and the protection efficiency reaches almost 100%.(4) Many results indicate that PANI powder electrode can provide Galvanic Anodic Protection to other metals besides lCrl3, such as carbon steel, 304, 316, 321 and so on. Generally, the Galvanic Anodic Protection effect of PANI is available to any passive ferrous metals.(5) Finally, the feasibility and security of the Galvanic Anodic Protection of PANI as a new applicable technology were discussed. The technology is highly efficient, cheap, easily operating and safe and may be extensively applied to protecting ferrous metals in acid solutions.The main innovations and specialties of this work are as follows:(1) The PANI powder electrode was first successfully made, which had good electrochemical properties, stability and mechanical intensity, and can be used repeatedly.(2) The passivation behavior and mechanism of PANI to metals were measured and studied by coupling PANI with ferrous metals. The experimental method was intuitionistic and reliable.(3) The concept about Galvanic Anodic Protection of PANI was first proposed. The Galvanic Anodic Protection of PANI to ferrous metals and the feasibility of this technology were studied experimentally.