Poly(amino-quinone)s: A new class of polymers for anticorrosive applications

Abstract

Metals or steel reinforced concrete structures, that are not by themselves inert to chemical attack (corrosion) from the environment in which they are designed to serve, can very rarely be protected by metallic coatings [1]. The normal protection under such conditions will be provided by a non metal, often by a polymer coating. Each polymer so used has its own limitations— chemical or thermal, which must be considered. Therefore, in any case, a combination of two or more properties in a given polymer is required to provide necessary ultimate protection to the metal or steel present in the concrete. An ideal corrosion-resistant coating would be the one that can adhere to a wet surface, resist moisture and temperature changes, is capable of binding to metals as well as silicaceous materials under wet conditions, and resists autoclaving [2]. The polymers for this application should also be chemically compatible with other known engineering plastics for flexible use. Our own work in this area is concerned with the identification and the development of hydrophobic polymers for corrosion resistance applications. Hitherto, most of the polymers used for this application are directly or indirectly based on acrylic, vinyl, epoxy, polyurethane, etc. We have focussed our attention on two aspects, viz., (i) to explore the use of hydrophobic polymers as precursors to corrosion resistance coatings and (ii) to evaluate them in inhibitor formulations. Among the many polymers presently used in corrosion resistance application, poly(amino-quinone)s (PAQ) is a unique class in the context of protecting metallic surfaces as they readily bind to the metal with sufficient affinity to displace water. This feature of PAQ opens up new vistas in protecting metal surfaces that form the part of ship hulls and steel reinforcement bars from sea water corrosion and fouling. One of the major attractive features of this class of polymers is its preparation from a host of amines and quinones available in plentitude. Hitherto known methods of synthesizing [3–5] this class of polymers by condensation polymerization involve several approaches and usually takes two or three steps [Scheme 1]. However, the above synthesis is not free from problems such as: