NACE - National Association of Corrosion Engineers Surface Preparation and Contaminants Questions and Answers

Question 1

A steel substrate was prepared for a critical immersion service coating.
After abrasive blasting, the inspector notices dark, tightly adherent, bluish-black patches on the surface.
What is this contaminant, and what is the primary risk if it is not removed?

Accepted Answer

Mill scale; it can detach, leading to premature coating failure.

Answer

Weld slag; it will create a brittle layer under the coating.

Answer

Soluble salts; they will cause osmotic blistering.

Answer

Oil and grease; they will prevent proper wetting of the surface.

Question 2

According to the joint NACE/SSPC standards, which of the following surface preparation methods does NOT inherently create a surface profile?

Accepted Answer

NACE No. 5 / SSPC-SP 12, High-Pressure Waterjetting

Answer

SSPC-SP 10 / NACE No. 2, Near-White Metal Blast Cleaning

Answer

SSPC-SP 11, Power Tool Cleaning to Bare Metal

Answer

SSPC-SP 5 / NACE No. 1, White Metal Blast Cleaning

Question 3

An inspector is qualifying a surface prepared to SSPC-SP 6 / NACE No. 3, "Commercial Blast Cleaning." According to the standard, what percentage of each unit area (e.g., 9 sq. in.) is permitted to have tightly adherent, residual staining?

Accepted Answer

Up to 33%

Answer

0%

Answer

Up to 5%

Answer

Up to 10%

Question 4

A coating project in a marine environment is experiencing premature failure in the form of blistering. The surface was abrasive blast cleaned to a near-white metal standard (SSPC-SP 10). Testing of the substrate underneath the blisters reveals a high concentration of chlorides. What is the most likely cause of this failure?

Accepted Answer

Soluble salt contamination was not removed prior to or during blasting.

Answer

The abrasive media was too angular, creating an excessive profile.

Answer

Flash rust occurred between blasting and coating application.

Answer

The coating was applied at too low a temperature.

Question 5

Which of the following is the primary purpose of SSPC-SP 1, Solvent Cleaning?

Accepted Answer

To remove visible oil, grease, soil, and other soluble contaminants.

Answer

To create a specific surface anchor profile for coating adhesion.

Answer

To remove all rust and mill scale from the substrate.

Answer

To remove non-visible contaminants like soluble salts.

Question 6

During surface preparation with power tools, an inspector is assessing if the remaining material is 'tightly adherent' as per SSPC-SP 7 / NACE No. 4, Brush-Off Blast Cleaning. What is the standard method for making this determination?

Accepted Answer

Observing if the material can be lifted with a dull putty knife.

Answer

Using a portable adhesion tester to measure the pull-off strength.

Answer

Striking the surface with a hammer to check for flaking.

Answer

Wiping the surface with a solvent-dampened cloth to check for residue.