NICET - Highway Construction Inspection Practice Exam

What should be applied to steel after it is cleaned but before painting?

1. Varnish

2. Sealant

3. Primer

4. Final coat

The correct answer is: Primer

Applying a primer to cleaned steel before painting is an essential step to ensure proper adhesion and durability of the paint. The primer acts as a preparatory coat that creates a bond between the clean steel surface and the subsequent paint layers. It helps to prevent rust and corrosion, especially when the steel is exposed to harsh environmental conditions. Primers often contain ingredients designed to promote adhesion and may include rust-inhibiting properties. This step is critical; if primer is not used, the paint may not adhere effectively to the surface, leading to chipping, peeling, or early degradation of the painted finish. Other elements like varnish or a final coat are not suitable for this initial stage, as they serve different purposes in the finishing process. Sealants typically apply afterwards for added protection but do not replace the function of a primer.