Relationship between coating properties and their performance on treated wooden decks
M Ahmadinejad, P A Cooper
Preservative treated wood benefits from the application of a surface coating to protect it from weathering (UV and rain). Different preservative formulations may affect surface properties of treated wood differently; therefore compatibility of coatings with different preservative treated wood types should be considered. This paper examines coatings characteristics and their weathering performance when applied on different treated wood surfaces. The performance of a range of semi-transparent stains on chromated copper arsenate (CCA), alkaline copper quaternary (ACQ) and copper azole (CA) treated Southern pine wood was monitored over 18 months of natural weathering in Toronto, Canada. Additionally, the samples were tested under accelerated weathering conditions over a three month period. The ability of these coatings to reduce water uptake and leaching and general appearance of coated wood were measured, and the correlation with coatings properties such as: resin type, solvent base, surface tension, viscosity, density, solid content and pH was tested. The results showed that all coatings significantly reduced water absorption and preservative component leaching and higher viscosity stains had better performance in general. The coatings performed differently on different preservative treatments. Relative leaching performance was similar for accelerated and natural weathering exposure.
Keywords: penetrating stain, leaching, preservative, weathering, CCA, ACQ, CA.