engleski

Modified Epoxy Coatings on Cast Iron

The application of organic coating on cast iron is one promising strategy for extending its service life by providing a passive physical barrier between the corrosive environment and metal surface. Among these protective properties of organic coating, epoxy coating is the most broadly applied material for industrial and engineering applications due to their advantages of good protection effect, simple method, good adhesion to metals, high corrosion resistance and low cost. However, water, oxygen and corrosive ions can diffuse into the epoxy resin through coating defects derived from improper curing, low cross-link density and local shrinkage resulting in coating delamination and substrate corrosion. Such wear can be seen in lower protective efficiency resulted from blistering, cracking, increase of pore volumes and number as well as from loss of adhesion to the substrate. Therefore, under the influence of aggressive media, epoxy coatings undergo both chemical and mechanical degradation which results in decrease of their operational durability. In this work, we modified an epoxy matrix into which we dispersed different concentrations (0.5%, 0.75%, and 1.0%) of aluminium nanoparticles (Al NPs) in order to extend the life of the coating and prevent the corrosion reaction on cast iron. Finely dispersed gray fluffy powder of aluminium nanoparticles enables a better interaction with the epoxy matrix. The microstructure of the obtained nanocomposite was observed by SEM and EDX analysis and it was determined that the coating shows a homogeneous and uniform distribution of nanoparticles. Anticorrosive properties were tested by measuring EIS in 3.5 wt.% NaCl solution for 24 hours. The sample containing 1.0% Al NPs shows the best resistance to the corrosive medium. All samples showed one semicircle with impedance values of one order (Al-0.5% and Al-0.75%) and two order (Al-1.0%) of magnitude higher than the control samples, indicating significantly improved resistance. By incorporating metal nanopowder into the epoxy matrix, the mechanical properties of the coating are improved, which is reflected in an increase in hardness. This application is also expected to create considerable economic benefits in industry in the future.

corrosion ; epoxy coatings ; aluminium nanoparticles ; electrochemical impedance spectroscopy (EIS)

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