Surface Preparation for Various Substrates Flashcards

What is the most critical first step when preparing a previously painted exterior wood surface that exhibits extensive peeling and flaking?

Answer: Scrape, sand, and feather all loose and peeling paint to a sound substrate.

Before any cleaning, priming, or painting can occur, the loose, failing paint must be physically removed. This creates a sound, stable substrate to which the new coating system can properly adhere, preventing premature failure of the new paint job.

What is the primary reason for cleaning new galvanized metal with a solvent or specialized cleaner before priming?

Answer: To remove the oily factory film that hinders adhesion.

New galvanized metal is often coated with a factory-applied oily film or passivation treatment to prevent white rust during storage and transport. This film must be completely removed because it will prevent paint and primers from adhering properly.

How should efflorescence, a white, powdery deposit on a masonry wall, be treated before painting?

Answer: Remove with a wire brush and wash with a specialized cleaner or dilute acid, then rinse thoroughly.

Efflorescence is caused by water-soluble salts migrating to the surface of masonry. It must be physically removed, typically with a stiff wire brush, and then washed. A dilute acid solution can help dissolve stubborn deposits, but thorough rinsing is crucial before painting.

What is the standard preparation sequence for new, un-textured drywall after taping and joint compound are fully cured?

Answer: Sand smooth, remove all dust, and apply a PVA or drywall primer/sealer.

The standard process ensures a smooth, uniform surface ready for paint. The joint compound must be sanded smooth, the resulting dust must be completely removed, and a PVA (polyvinyl acetate) primer is then applied to seal the porous surfaces of both the paper and the mud, ensuring the topcoat has a uniform sheen.

Before painting new, unpainted exterior wood, its moisture content should ideally be below what percentage?

Answer: 15%

Painting wood with high moisture content can trap water, leading to blistering, peeling, and rot. Most paint manufacturers and industry standards recommend that the wood's moisture content be 15% or lower to ensure proper paint adhesion and long-term durability.

Which SSPC standard for surface preparation of steel involves abrasive blast cleaning to remove all visible oil, grease, dirt, rust, and paint, but allows for slight stains to remain?

Answer: SSPC-SP 6 (Commercial Blast Cleaning)

SSPC-SP 6, or Commercial Blast Cleaning, is a common standard for industrial coatings. It provides a surface clean enough for most high-performance systems without the expense of a near-white (SP-10) or white metal (SP-5) blast.