Chapter 20 - Coating Defects

Question 1

Some of the problem that can be caused by amine blush are?

Answer 1

Surface tacking or greasiness
Incomplete curing
Poor adhesion
Coating discolouration 
Poor gloss retention

Question 2

Runs, sags, and wrinkles may be caused by?

Answer 2

Applying the coating too thick
Too much or the wrong thinner used
Surface too hot to apply the coating
Application of the coating at the end of its pot life
Wrong thixotope used in manufacturing

Question 3

_________is a powdery, friable layer on the surface of a coating that is most common with epoxy coatings.

Answer 3

Chalking

Question 4

Cratering may be caused by?

Answer 4

Air trapped in the coating and forming a bubble which then bursts
Air trapped in the coating during mixing if the proper procedures are not following

Question 5

Vacules or voids are typically caused by?

Answer 5

Running the mixer to fast

Question 6

Pinholes are?

Answer 6

Very small holes in a coating typically caused by air or solvent trapped in porous film and escaping

Question 7

A common cause of blistering is?

Answer 7

Surface contamination under the applied coating

Question 8

Cracking of a coating is noted?

Answer 8

When the crack extends to the substrate

Question 9

Checking can be described as?

Answer 9

Fine cracks in the surface of a coating that don’t extend through to the substrate

Question 10

Adhesion failures may be caused by

Answer 10

Contamination on the surface
Wrong surface preparation specified
Failure to inspect surface preparation 
Insufficient surface profile
Exceeding the topcoat window
Application if incompatible coating

Question 11

Failure of coating to cure may be caused by?

Answer 11

Not adding curing agent, wrong curing agent or incorrect amount of it

Problem with material from the manufacturer

Environmental issues ( too cold, hot, or humid)
Wrong or contaminated thinner (solvent)