Coating Application Techniques Flashcards

When spraying a large flat steel surface by conventional or airless spray, what overlap between passes is generally recommended to achieve uniform film thickness?

Answer: About 50%

A 50% overlap on each pass helps even out the thinner film at the edges of the spray fan and gives uniform DFT.

An airless spray tip is marked 517. What does the '17' indicate?

Answer: Orifice diameter of 0.017 inch

In common airless tip coding the last two digits give the orifice size in thousandths of an inch, so 17 means 0.017 in.

What is the main purpose of applying a stripe coat before the full coat?

Answer: Add extra film build on edges, welds, and corners where spray film tends to be thin

Stripe coating by brush or roller adds film to edges, welds, bolts, and crevices, where film pulls back and goes on thin.

Holding a spray gun at an arc (pivoting the wrist) instead of moving it parallel to the surface usually causes what?

Answer: Thin film at the ends of the stroke and heavy film in the middle

Arcing changes the gun-to-surface distance, so the film goes on heavy where the gun is close and thin at the ends of the stroke.

For airless spray, what gun-to-surface distance is commonly recommended?

Answer: 12 to 18 inches

Airless guns are typically held about 12 to 18 inches from the surface to balance atomization, transfer efficiency, and film build.

A coating has 65% volume solids, and the specification calls for 4 mils DFT. If no thinner is added, what WFT should the applicator aim for?

Answer: About 6.2 mils

WFT = DFT ÷ volume solids = 4 ÷ 0.65 ≈ 6.2 mils.

Which application method usually gives the highest transfer efficiency for liquid coatings in the field?

Answer: Brush application

Brush and roller put almost all of the material on the surface, though they are slower and build less film per coat.