What is the recommended thickness for applying the topcoat?

• A. 2-4 mils
• B. 4-8 mils
• C. 6-12 mils
• D. 8-10 mils

Answer: (B)

Applying the topcoat in a four-to-eight mils range gives a solid barrier without inviting application defects. This thickness is enough to cover surface imperfections and provide good resistance to moisture and chemicals, while still flowing smoothly to a uniform finish as it cures. If you go thinner, like two to four mils, the film may not fully seal or protect the substrate, leaving gaps in coverage and reducing corrosion resistance. If you go thicker, especially beyond eight mils, the coating is more prone to runs, sagging, and longer cure times, and it may trap solvents or develop an uneven surface. In practice, follow the coating’s data sheet, but four to eight mils is the balance that works well for most topcoats.