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1 Introduction
In general, a paint coating can be defined as any liquid, liquefiable or mastic composition that is converted to a solid film after application of a thin layer to a substrate. The paint coating protects metallic surfaces by acting as a barrier between the metal and the environment. Primarily, a paint coating consists of pigments and a binder, such as epoxy resin. Epoxy resin is the binder of choice due to its low cost and good physical properties. Paint coatings are typically non-conductive; however, in certain cases, a low cost thin conductive film (coating) with good electrical and physical properties is required, especially for the development of transportation and electronic technologies ([1] Azim et al. , 2006; [4] Leong and Chung, 2006).
In recent years, there have been extensive studies on resin-based conductive coatings. The most common conductive fillers are graphite ([1] Azim et al. , 2006; [9] Zheng and Wong, 2003), carbon black-silver ([4] Leong and Chung, 2006), silica ([8] Zhang et al. , 2007), short carbon fibers ([6] Tsotra and Friedrich, 2004), carbon nanofibers ([3] Johnson et al. , 2003), and silver-coated carbon nanotubes ([7] Wu et al. , 2007).
The work described in this paper is focused on the electrical conductivity and corrosion resistance of a conductive coating composed of epoxy resin and carbon black. Thus, the objective of the work was to study the conductivity and morphology of the coating in order to develop a structure-activity relationship, and to test the conductive epoxy resin carbon black material when applied to a mild steel system in a corrosive environment.
2 Experimental
2.1 Coating preparation
The conductive coating was prepared by mixing epoxy resin (ER, DER113, Dow Chemical Co.) with polyamide (A062, Eastech). The ratio of epoxy resin to polyamide was 1:1, and xylene used as a solvent. Table I [Figure omitted. See Article Image.] shows the materials used in the preparation of the conductive coating. Carbon black, with a particle size of 4.26 μ m, was used as the conductor. The concentration of carbon black required in the conductive coating (CB, N220 Cabot Corporation) was calculated using the following formula: Equation 1 [Figure omitted. See Article Image.]
2.2 Coating characterization
Electrical conductivity tests were conducted on an advance test machine...