Synthesis and characterization of functional polymers with controlled architecture and their application as anticorrosion primers

There are over 2900 ballast tanks in the U.S. Navy inventory and their annual maintenance cost amounted to 415 million dollars in 2006, half of which was directly correlated to corrosion. Ballast tanks which form the basic skeleton of a vessel, are subjected to very corrosive conditions. Epoxy based protective coatings are used by the Navy for minimizing corrosion and they currently offer five to seven years of protection. The work described in this thesis is in line with a major program instigated by the U.S. Navy to improve the reliability of tank coatings. This thesis investigates the synthesis and use of carefully designed functional poly(methacrylate) copolymers as a primer coating addressing one of the major failure mechanisms responsible for corrosion: delamination of the coating at the steel-coating interface. Novel polymers were designed and synthesized to improve corrosion protection and adhesion of epoxy coatings to steel. They possess two types of functional groups which are incorporated in the polymer and distributed in blocks or other related structures. One block is designed to bind strongly to the metal substrate and therefore protect that surfaces from corrosion, the other block possesses the ability to interact with the bulk coating. The epoxy coating and the metal surface are therefore linked through a series of strong durable polymeric bonds. Several monomers possessing either a metal chelating group or a group allowing blending with the coating were thus prepared. Block copolymers and other polymer structures were synthesized by nitroxide mediated polymerization, a polymerization technique that allows control of the molecular weight and architecture. An AEMA-GMA block copolymer was synthesized in a two-step process and gradient copolymers were synthesized in a one-pot synthesis. Copolymer anti-corrosion properties were then evaluated through a series of tests (salt spray, hot water immersion, cathodic disbondment, electrochemical impedance spectroscopy, polarization curves and pull-off test). A deposition method was developed to generate the optimal coating system: the steel to protect was dipped in a dilute solution of the copolymer, rinsed with pure solvent to eliminate the excess material and painted by spraying the epoxy mixture. Electrochemical techniques showed a 60% corrosion inhibition for the AEMA-GMA copolymers. An improvement of the epoxy coating corrosion resistance with the addition of the AEMA-GMA gradient copolymer and the AEMA-GMA star-block copolymer was noticed when subjected to hot water immersion and salt spray tests. While the polymeric primers showed to be quite effective in improving the coating\u27s corrosion resistance, the common corrosion resistance tests were found to be inadequate to robustly characterize their full potential. Nonetheless, the functional copolymers polymer with controlled architecture, their formulation and improved testing techniques, present challenging and interesting work to continue for anticorrosion research