Cathodic delamination of polymer coatings from metals. Mechanism and prevention methods. A review
Unknown authors
Abstract
The phenomenon of cathodic delamination of protective polymer coatings from a metal and the development of methods for its prevention are important scientific and technical problems in the operation of underground and underwater metal structures protected from corrosion by insulating polymer coatings.A review of scientific and technical literature on the cathodic delamination of anticorrosive polymer coatings from metals is presented.The possible mechanisms of cathodic delamination are considered, including the cathodic reduction of a metal oxide, electrochemical destruction of a polymer layer adjacent to the surface, destruction of interphase bonds under chemical attack by cathodic reaction products, and mechanical action of gaseous molecular hydrogen formed at the metal-polymer interface due to the cathodic reduction of water.The following factors that determine the rate of this process are identified and discussed: the potential of cathodic protection, thickness of the polymer coating, temperature, ionic composition of the electrolyte, and time of testing or operation of a structure under working cathodic protection.The methods for inhibiting cathodic delamination presented in the literature are briefly described.The mechanism of inhibitive action of surface layers that are formed on a metal upon pretreatment and efficiently slow down the delamination of a polymer coating under cathodic potential is considered.Various methods for the modification of coatings are discussed, namely: incorporation of pigments, adhesion promoters, corrosion inhibitors, conductive polymers, or functionalized particles of graphene oxide or carbon nanotubes into the coating bulk, etc., are considered.The effect of various methods of coating modification on the adhesion in the dry state, water resistance of coating adhesion, liability of the coating to cathodic delamination, and anticorrosion characteristics of the coating are considered.