Environmental Integrity of Coating/Metal Interface.
Abstract
Corrosion of polymer coated steel in neutral media entails the initiation of anodic dissolution of the metal at defects in the coating with the cathodic reduction of oxygen at the adjacent interface. The cathodic reduction of oxygen produces a buildup of NaOH at the interface which enhances adhesion loss which leads to the propagation of corrosion. In-situ acoustic microscopy of a coating undergoing cathodic disbonding at constant potential has allowed evaluation of both the kinetics and microscopic structure of the disbond front with detail not previously attained. Disbonding of a hydroxy-terminated polybutadiene coating from polished and degreased steel in 0.5 M NaCl has been examined in-situ as a function of applied potential. The results show that potentials more negative than -550 mV vs Ag/AgCl accelerate disbonding by the formation of a weak fluid boundary layer at the coating/metal interface just ahead of electroosmotically produced approximately 50 micro m blisters. Concentration of NaOH in the microblister weakens the polymer metal interface while the osmotic pressure in the microblisters provides the mechanical force necessary to rupture the coating/metal bond. Keywords: Organic coating, Corrosion, Cathodic disbonding, Acoustic microscopy, Polynbutadiene, Adhesion, Carbon steel.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1988
- Accession Number
- ADA192184
Entities
People
- M. Kendig
- R. Addison
- S. Jeanjaquet