Surface Preparation for Various Substrates Flashcards

A painter is preparing weathered cedar siding that has turned gray. What is the primary purpose of using a wood brightener/cleaner on this surface?

Answer: To restore pH balance and open wood fibers for better coating penetration

Wood brighteners (typically oxalic acid-based) restore the wood's pH and open the grain after weathering, improving penetration and adhesion of subsequent coatings.

When preparing a brick masonry surface that has been coated with silicone-based water repellent, what challenge does the painter face?

Answer: Paint will not adhere because silicone repels water-based and most solvent-based coatings

Silicone water repellents create a non-porous, low-surface-energy barrier that prevents most paints from adhering, requiring mechanical removal or a specialized bonding primer.

According to best practices for the C33 license, what is the purpose of 'feathering' edges when spot-sanding a previously painted surface?

Answer: To blend the repair area seamlessly with the surrounding surface to avoid visible edges under the new paint

Feathering tapers the edges of a sanded or filled repair so it blends smoothly with the surrounding surface, preventing ridge lines from showing through the topcoat.

A contractor is repainting a swimming pool deck coated with chlorinated rubber paint. What is a critical compatibility concern during surface preparation?

Answer: Solvent-based cleaners can re-dissolve the existing chlorinated rubber film, causing lifting

Many solvent-based cleaners and coatings will attack and dissolve existing chlorinated rubber films, causing lifting and wrinkling, so compatibility testing is essential.

What does the term 'flash rusting' refer to when preparing steel surfaces, and how is it addressed?

Answer: Rapid rusting that occurs on wet-blasted steel before the primer can be applied, requiring immediate priming or a flash-rust inhibitor

Flash rusting is rapid surface oxidation that forms on wet-blasted or water-washed steel within minutes; it is controlled by priming immediately or using a flash-rust inhibitor in the wash water.

When preparing a fiberglass substrate (such as a door or boat hull) for painting, which surface preparation step is uniquely critical compared to wood or metal?

Answer: Sanding to remove the gel coat's mold-release wax and create mechanical adhesion

Fiberglass gel coat contains mold-release agents that prevent adhesion; the surface must be thoroughly sanded to remove the wax layer and create a mechanical profile for the primer.

Under California's VOC regulations, which surface preparation activity requires the use of compliant low-VOC or exempt solvents when cleaning substrates before coating?

Answer: Solvent wiping of metal to remove oils and contaminants

California Air Resources Board (CARB) regulations restrict the VOC content of surface preparation solvents used to clean substrates before coating, requiring compliant or exempt-solvent products.