Characterising inhibitor storage and release from commercial primers
A high solid primer that contains strontium chromate (SrCrO4), a Pr-based and a BaSO4-based primer were coated on a Teflon tape, then stripped off and broken to small pieces. Pieces of the primer coating were immersed into solutions of different Cl− concentration, temperature, time, and pH.
Plentiful reservoir of Cr inhibitor
Results showed that SrCrO4 primer release behaviour follows power law kinetics. Solubility limits played an important role in dictating the release kinetics of the chromate primer when accumulation of Cr ion occurs. The effect of pH and temperature can alter this solubility limit. Chloride seems to promote release of chromate because of greater ionic strength. The Pr-rich primer released a large amount of Ca2+ upon exposure and release kinetics were not time-dependent thereafter. The Ba-rich primer did not release soluble constituents to any significant extent.
The study is published in: Progress in Organic Coatings, Vol. 114, January 2018.