Preparation And Corrosion Resistance Of Polyaniline And Its Oxide Composite Film

Metal corrosion refers to the metal failure caused by chemical or electrochemical reaction between a metal and its surrounding medium (mainly electrochemical reactions). Metal corrosion phenomenon is very common. It not only causes enormous economic losses, but also give rise to many catastrophic accidents, which seriously hampers the development of society. Therefore, finding a cheap, efficient and environmental friendly mean to prevent corrosion has been a research focus in the field of corrosion protection. Due to its superior properties, such as easy to synthesis, high conductivity, easy doping and good corrosion resistance, etc., polyaniline (PANi) has been of great concern.In this paper, phosphoric acid doped PANI film on the surface of stainless steel was prepared by electrochemical oxidation. How proton acid concentration and electrochemical polymerization time influences the morphology and corrosion resistance of the PANI film was also investigated. The study revealed that PANI film can make the corrosion potential stainless steel significantly positively shifted when the phosphoric acid concentration is1.5mol/L and the number of scan cycle is20. The synthesized PANI makes the corrosion current density of stainless steel decrease from289μA·cm-2to7.8μuA·cm-2, and the protective efficiency is calculated to be97.3%.In order to improve the corrosion resistance of PANI, SiO2and TiO2nanoparticles were utilized In the process of synthesis. The PANI/SiO2and PANI/TiO2composite film were synthesized on stainless steel by cyclic voltammetry. And influence of the adding amount of nanoparticles and polymerization time on morphology and electrochemical properties of the composite film was also studied in this paper. Physical characterization showed that the composite film are denser and has a better physical structure. The electrochemical tests showed that, when the SiO2particles concentration is7g/L, the corrosion current density of PANI/SiO2composite film has a minimum value,2.65μA· cm-2. For TiO2, when the scan cycle is30, the charge transfer resistance (Rct) of PANI/TiO2composite film reached12160Ω cm2, which is nearly two orders of magnitude higher than the bare stainless steel increased by, and that is also much higher than that of PANI,4066Ω·cm2. All test results show that the SiO2or TiO2modified PANI composite coatings provide a better corrosion protection for stainless steel substrate. Finally, sulfate reducting bacteria (SRB) are cultured in laboratory. Soaking the synthesized PANI/TiO2composite film in a SRB-contained medium for different days, the microbial corrosion resistance was studied by comparing the biofilm morphology, the corrosion morphology and the electrochemical behavior of stainless steel and PANI/TiO2composite film. The experimental results showed that PANI/TiO2composite film can significantly improve the microbial corrosion resistance of stainless steel in SRB-contained medium.