Polymer Film Coatings on Metal Electrodes Through Electroinitiated Polymerization and Their Evaluation

Abstract

Adherent films of polymers on different metal surfaces are formed by the electroinitiated polymerization of acrylonitrile alone and of mixtures of acrylonitrile and acrylic acid in aqueous solution. Five different metals—aluminum, nickel, copper, stainless steel and steel—are used as the cathodes for purposes of the coatings while platinum plate is the anode in each case. The electrolysis is carried out under a constant voltage. After the electrolytic runs, the coatings are scraped off the metals for infrared analysis to establish the functional groups. Furthermore, the scanning electron microscope (SEM) is used to examine the structure of the film surfaces. The effects of variable monomer concentrations and polymerization voltages on thickness and appearance of the film are also investigated. Corrosion tests are performed to compare the corrosion resistance of coated and uncoated metals in various corrosive solutions, through both the weight‐loss and the electrochemical methods. It is observed that good and uniform coatings always reduce the corrosion rate of the metals (e.g., coated nickel and copper). However, porous coatings are seen to accelerate the corrosion rate of the support metals (coated aluminum, for example). Also, it is observed that the monomer concentration and voltage for the electroinitiated polymerization process have some influence on the corrosion resistance of coated metals. All of these phenomena are explained through the surface structure and thickness of the coatings,