Corrosion control coatings

Architectural coatings are applied on new and existing residential, commercial, institutional, and industrial buildings. Small percentages of these are used as primers and undercoats and may be classified as corrosion control coatings. Architectural coatings are water-based and water-thinned. Some data on architectural coatings sold in 1997 in the United States are as follows in Table 4.2. 

Special-purpose coatings include heavy industry corrosion control coatings as well as marine and automotive refinishing. The distribution of corrosion-related special-purpose coatings is shown in Table 4.4. 

The value of special-purpose corrosion control coatings represents 79% of the 2896 billion special-purpose coatings market in 1997. 

TABLE 4.5 Summary for Corrosion Control Coatings Sold in 1997... 

Total special purpose corrosion control coatings 2298... 

Human actions such as the actions of owner and crew during the operation of the ship are the last element of corrosion control. Coating represents the most important part of corrosion control on a ship and hence maintaining the integrity of the coating during operation is vital to corrosion control. 

All three types of polymers have been and continue to be investigated for use in corrosion control coatings, either directly as a primer coating or surface treatment or as one of the components of conventional coatings. 

FIGURE 15.1 Neutral (undoped) forms of parent-conjugated polymers that have been studied as corrosion control coatings. 

Soluble conducting polymers can be solvent cast to form coatings. The addition of appropriate substituents to the polymer backbone or to the dopant ion can impart the necessary solubility to the polymer. For example, alkyl or alkoxy groups appended to the polymer backbone yield polypyrroles [117,118], polythiophenes [118], polyanilines [119,120], and poly(p-phenylenevinylenes) [97] that are soluble in common organic solvents. Alternatively, the attachment of ionizable functionalities (such as alkyl sulfonates or carboxylates) to the polymer backbone can impart water solubility to the polymer, and this approach has been used to form water-soluble polypyrroles [121], polythiophenes [122], and polyanilines [123]. These latter polymers are often referred to as self-doped polymers as the anionic dopant is covalently attached to the polymer backbone [9]. For use as a corrosion control coating, these water-soluble polymers must be cross-linked [124] or otherwise rendered insoluble. 

An electrically conductive polymer composite of polypyrrole and poly(ethyl methacrylate) has been prepared by an emulsion polymerization procedure [ 142]. In this case, the relation between conductivity and the polypyrrole content of the composite exhibited a percolation behavior, with conductivities as high as 6-7 S/ctn. Such composites might be amenable to melt processing for coating formation. Composite films consisting of polypyrrole or poly(N-ethylaniline) filler dispersed in a polyimide matrix have been described for potential use as corrosion control coatings for the A1 alloy AA 2024-T3 [143]. 

Approved Prefabrication Primers and Corrosion Control Coatings, Lloyds Register of Shipping, London (1983). 

Yan, M.C., TaHman, D.E., Rasmussen, S. C., and Bierwagen, G.P. (2009) Corrosion control coatings for aluminum alloys based on neutral and n-doped conjugated polymers./. Electrochem. Soc., 156, C360-C366. 

Proceedings of the Wear and Corrosion Control Coatings for Automotive Applications Symposium, Society of Manufacturing Engineers, Dearborn, MI, 1996. 

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