COATINGS
David A. Hunter, Managing Director Asia Pacific, NRI
How important is surface
preparation?
The quality of the surface preparation is critical. All
other things being equal, the cleaner the surface, the longer the
coating lasts. Coatings stick to surfaces primarily by a covalent
bond, which is a sharing of electrons. The bond strength is
inversely proportional to the distance between them. Any
contaminants that might put distance between the coating and
the surface reduce bond strength, and potentially allow space
for containments that may penetrate through the coating.
Contaminates can be visible or invisible. Good quality control and
quality assurance can help insure that surfaces are prepared per
industry-accepted standards.
Coatings application is the one construction discipline that is
extremely difficult to verify after the fact. Education on industry
standards, and their proper usage, is available through organisations,
Figure 1.
Industry standards, such as the joint standards for
surface preparation by NACE International and SSPC, The
Society for Protective Coatings, highlight the importance of a
clean substrate to a quality coatings project.
Figure 2.
Regardless of how carefully the coating is applied,
if contaminates are left on the surface, the coating will most
likely prematurely fail.
Figure 3.
Whether in the field, or in a factory setting, quality control and third-party inspection help verify that the specifications are
being followed and that the standards are being met.
SEPTEMBER
2014
63
