Surface Preparation Flashcards

Which method is commonly used to remove rust and old coatings from a metal surface before applying a new protective coating?

Answer: Abrasive blasting

Abrasive blasting, also known as sandblasting, is a highly effective method for surface preparation. It uses a stream of abrasive material propelled at high velocity to remove rust, old coatings, mill scale, and other contaminants from metal surfaces. This process creates a clean and roughened profile, which is essential for proper adhesion of new protective coatings.

Why is surface profile important in protective coatings application?

Answer: Ensures proper coating adhesion

Surface profile refers to the microscopic roughness or texture of a prepared surface. A proper surface profile, typically created by methods like abrasive blasting, provides a mechanical anchor for the coating to grip onto. This significantly enhances its adhesion to the substrate, preventing premature delamination or coating failure.

Which standard is commonly used to classify cleanliness levels for abrasive blasting?

Answer: SSPC/NACE

SSPC (The Society for Protective Coatings) and NACE International (now AMPP) are leading organizations that develop standards for surface preparation and coating application. Their joint standards, such as SSPC-SP and NACE No., define various levels of cleanliness and surface profiles for abrasive blasting. These standards ensure consistent and high-quality preparation for protective coatings.

What is the main purpose of solvent cleaning before coating application?

Answer: Removes contaminants for better adhesion

Solvent cleaning is a crucial step in surface preparation, typically performed after abrasive blasting or as a standalone method for lighter contamination. Its main purpose is to remove soluble contaminants like oils, grease, salts, and other residues. These contaminants could otherwise interfere with coating adhesion and lead to premature coating failure.

Which type of abrasive material is commonly used for blasting in surface preparation?

Answer: Garnet

Garnet is a commonly used abrasive material for blasting in surface preparation due to its hardness, angular shape, and low dust generation. It provides an excellent surface profile for coating adhesion, is environmentally friendly, and can be recycled. These properties make it a popular choice in the protective coatings industry for achieving optimal surface readiness.

Why is humidity control important during surface preparation for coatings?

Answer: Prevents flash rusting

Humidity control is critical during surface preparation, especially after abrasive blasting of ferrous metals. High humidity can cause flash rusting, where the freshly cleaned metal surface rapidly oxidizes and rusts before the coating can be applied. Controlling humidity prevents this immediate corrosion, ensuring a clean and reactive surface for optimal coating adhesion.