Vapor and water permeabilities and moisture absorbability of organosilicate coatings

Abstract

A setup was designed for determining the vapor and water permeabilities of coatings and films on porous metal substrates at temperatures of 40°C and higher. The setup was used to determine the vapor and water permeabilities of five organosilicate coatings, namely, OS-51-03 (green), OS-51-03A (green), OS-11-07 (green), OS-11-07A (green), and OS-12-03 (white). The thickness of the coatings was in the range 90–130 μm. The water permeability of all the coatings under investigation was found to be higher than their vapor permeability. The lowest vapor and water permeabilities were observed for the OS-51-03 coating (the vapor permeability was 2.76 × 10−5 mg/m h Pa). The moisture absorption of the green coatings, the OS-12-03 white composite, and the varnish coatings based on the KO-921 varnish and a mixture of the KO-915 and KO-075 varnishes were investigated. No correlation between the moisture absorption and the water permeability was revealed. It was established that the KO-921 varnish coating possesses the lowest water absorbability (0.85%).