By Kenneth Tator, PCS, KTA-Tator, Inc.
Presented at SSPC 2014; Session: Coating Failure Investigations; Session chair: Charlie Brown, Greenman-Pedersen, Inc.
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An accurate and comprehensive coating failure analysis often hinges not only on the quality of the field investigation and the laboratory analysis, but also on effective communication between the field analyst and the forensic laboratory.
Several steps can be taken during a field investigation to ensure that samples of coating removed for laboratory analysis fairly represent the condition of the coatings and give the forensic laboratory the best possible chance of discovering the root cause of the coating failure. Sampling techniques vary depending on the nature of coating failure, the physical condition of the coating (i.e. adhesion, thickness, hardness, etc.), the anticipated laboratory analytical technique, and the nature of the coated substrate. The first step involves developing a sampling strategy. Among other considerations, the strategy involves the sampling of coatings in appropriate areas of failure as well as in areas where no failure has occurred coating. A second step involves the physical removal of coating samples to maximize the effectiveness of the subsequent laboratory examination. No single sampling technique is universally effective.
Effective communication between the field analyst and the laboratory analysts is critical. In most cases the decision on which laboratory analytical methods to employ depend on both the observations made during the failure analysis field investigation, and on the preliminary microscopic examination of the coating samples. The observations made in the field and the microscopic observations are generally made by two different people with a differing understanding of the nature of the coating failure. Both the field analyst and a laboratory analyst must communicate their understanding of their observations to each other in order to develop an effective laboratory testing scheme.