CSLB C-33 Painting & DecoratingSurface PreparationMedium
A painting contractor is preparing an exterior PVC trim board for painting. The trim is new, clean, and appears smooth. What is the most important step to ensure long-term adhesion of the paint to this non-porous surface?
- AWipe the surface with a tack cloth to remove dust.
- BLightly abrade (scuff sand) the surface with fine-grit sandpaper.
- CClean the surface thoroughly with soap and water.
- DApply a solvent-based degreaser to remove manufacturing residues.
Show answer & explanationAnswer & explanation
Correct answer: B. Lightly abrade (scuff sand) the surface with fine-grit sandpaper.
PVC is a very smooth, non-porous plastic. Lightly scuff sanding creates a mechanical profile (tooth) for the primer or paint to adhere to, which is crucial for long-term adhesion on such a slick surface.
Why the other options are wrong
- A. A tack cloth is for dust removal, which is a final step before painting, not a primary adhesion promoter for slick surfaces.
- C. Cleaning is necessary for any surface, but it doesn't create the mechanical bond needed for PVC.
- D. While degreasing is good practice, especially for new materials, it does not create the necessary surface profile for adhesion on slick PVC.
PVC Surface Preparation
The process of treating PVC (polyvinyl chloride) surfaces to ensure proper adhesion of primers and paints, typically involving cleaning and mechanical abrasion.
- PVC is non-porous and requires special preparation.
- Scuff sanding creates a mechanical 'tooth' for adhesion.
- Specific primers (adhesion or bonding) are often recommended.
Memory trick: Smooth PVC needs a scratch to grip, then paint will stick and never slip.