“The Case of… Three (Consultants),” a two-part F-Files column published in the November and December 2010 issues of JPCL,1 described observations and conclusions reached by three different consultants, each looking at the same bridge coating system. The article pointed out that clients sometimes retain consultants to perform very specific and limited examinations of the alleged failing coatings. Clients may also request reports that address specific issues, questions, or requirements.
This month’s column describes a set of circumstances that forces us further down the path, where a difference of opinion exists “before the sun sets.” Sometimes the differences of opinion are legitimate and arise from alternative but reasonable interpretations of data and available information—other times, not so much.
Conducting 200 to 300 investigations over the past ten years has provided me the opportunity to experience situations in which multiple parties investigate the same failures. While many such occasions have been interesting and educational, I have encountered a number of repeat problems in the way that coating failure investigations are performed. When two investigators, knowledgeable in coatings science, perform their respective investigations objectively, there generally should be many aspects of the two investigations that are consistent. There may be minor differences in field data, criticisms in the conduct of certain assessments, or even the identification of some areas that could be expounded upon. Most assuredly, there will be some differences in opinion (often related to the question being answered), but on the whole, the two investigations generally align at least in the actual test results and measurements.
However, there are instances when an opposing technical expert spends little time actually evaluating the condition of the coating and seeking the “root cause” of failure. Rather, his primary responsibility is seeking out [perceived] shortcomings in the work performed by the other investigator(s) to discredit the work product. This “adversarial evaluation” is accomplished primarily by attacking the technical methods/procedures used or not used by others during the collection of information and development of opinions on the cause of failure. These types of adversarial evaluations are all too often performed by inexperienced individuals whose primary knowledge base lies in the industry standards. The individuals may or may not be well trained, and may have many years in the field but are unable to grasp the nuances of objective investigation, something quite different from objective inspection. The critical drawback appears to be little understanding of the applied science behind technical properties (chemical and physical) of coatings and reliance instead on consensus standards or subjective requirements.
The adversarial approach is also a hallmark of investigators who serve as hired gun consultants. These individuals may spin or ignore data and exaggerate findings to support the interest of their client. One investigator went so far as to propose one fee for performing the failure investigation and a different, significantly higher fee for “winning the case.” I have observed that these practices are reckless and often do not hold up in court. In contrast, an objective, well-reasoned, and clear presentation of facts that support all reported conclusions (i.e., the role of an expert witness) contributes to success in almost every instance. Below are examples in which strict reliance on consensus standards or subjective requirements differs from forensic investigation.
Misuse of a Coating Thickness Standard
One of the most commonly used arguments to discount the technical findings of a failure investigation (when the
failure relates to coating thickness) is that the investigator did not perform measurements at the frequencies prescribed by SSPC-PA 2, Measurement of Dry Coating Thickness with Magnetic Gages. The SSPC-PA 2 standard was developed for installation of new or maintenance coatings. It provides frequencies for performing thickness measurements and tolerance of spot and area measurements to help assure that the application is compliant with the coating specification. Its implementation prevents over-inspection of coating thickness.
When a coating or lining system is failing prematurely however, more frequent measurements are warranted in certain areas to identify and isolate problem areas, while no measurements may be needed in other areas. Some investigators attempt to devalue another investigation that included more frequent measurements (in both failing and non-failing areas) by stating that the measurement frequencies identified in SSPC-PA 2 were not followed and the measurements were not random. Other investigators have manipulated the thickness measurement locations to demonstrate compliance with the specified thickness. For example, SSPCPA 2 requires five separate spot measurements (average of three gage readings) spaced arbitrarily over each 10 m2 (100 ft2) area to be measured. (The number of areas depends on the size of the structure being coated.) The standard does not specifically state that the spot measurements must be spaced uniformly across the test area, so some investigators will take the five spot readings within a small area, perhaps where the coating thickness conforms to the specification, rather than acquiring readings across the entire surface. In the end, both of the practices discussed above are usually discounted during mediation or trial, and a logical approach to identifying the problem areas usually wins.
SSPC Committee C.3.2 is revising the dry film thickness standard (PA 2, expected to be published in 2012). Among the proposed revisions are explicit directions that the standard is not intended to require how frequently coating thickness measurements must be taken for coating failure investigations nor where such measurements must be taken.
Further, the frequency of measurement acquisition might be removed from the standard practice, ASTM D7091, in its next revision (also expected to be published in 2012). If the proposed revision is accepted, it will then be appropriate to reference the ASTM D7091 standard for coating failure investigations because it focuses primarily on proper gage use.
Misuse of Adhesion Data
Another approach used to discount sound investigations is the insistence on performing tensile adhesion tests to assess a coating’s acceptability. Some investigators have argued that tensile adhesion values are frequently listed on the manufacturer’s product data sheet, so the tensile adhesion test is the only adhesion test appropriate to evaluate a coating’s acceptability. What must be recognized is that the values listed under “Performance Testing” on a data sheet are typically generated on a coating system applied in a laboratory under ideal conditions and are primarily listed to improve the marketability of the coating itself. The information is not generally listed as an “acceptance criteria” for minimum performance, and it should not be used as the sole means of determining suitability or assessing risk of failure when conducting an investigation. For example, a coating system can withstand significant tensile forces but may be able to be lifted off of the substrate by slight prying with a knife blade (Fig. 1).
An experienced investigator can learn more about the integrity of a coating system by probing with the blade of a knife than performing tensile adhesion tests. Further, coatings do not typically fail by separation perpendicular to the substrate surface (tensile forces). To the contrary, most failures are initiated by shear forces—peeling forces that are more parallel to the coated surface. Perhaps the undercutting that extends from the leading edge of a coating defect is the best example of this type of shear failure. When there is a leading edge of coating, moisture can penetrate the edge, initiate corrosion of the substrate, and push the coating off of the surface. There are numerous instances where tensile adhesion testing was performed as part of a coating failure investigation that resulted in pull-off values in excess of 2,000 psi. However, when shear adhesion testing2 was performed, poor adhesion properties were revealed. In these instances, one investigator concentrated on the tensile adhesion values and ignored the results of the knife adhesion tests. (He also ignored the fact that both the tensile and knife adhesion tests were conducted adjacent to failed coating where continued failure was expected and predicted by the knife adhesion tests.)
Certainly there is a place for tensile adhesion testing; however, when other adhesion tests predict failure at the same location as “good” tensile adhesion results, complete reliance on the tensile adhesion tests should be avoided.
In addition to the misuse of tensile adhesion data, one investigator discounted all of the tape adhesion test data collected by another based on minimal deviations from the ASTM standard (e.g., length of incisions), despite the fact that the tape adhesion testing clearly identified areas that subsequently failed.
Failure Mechanism Identification without Forensic Evidence
The adversarial evaluation also goes beyond misuse of industry standard test methods and procedures. Some investigators will claim to identify the cause of a coating failure without actually performing any forensic analysis (laboratory testing), despite the fact that laboratory testing is necessary and appropriate, in most cases3, to forming a hypothesis. Can you imagine a crime scene investigator who elects not to use forensic evidence to prove the case? Laboratory forensic analysis is essential for bringing meaning to the investigation by providing (or confirming) facts about the failure. This analysis serves several purposes:
- confirms field testing such as coating thickness measurements and number of coating layers,
- identifies visible and non-visible contaminants (which may or may not be detected in the field),
- verifies the type of coating that was [actually] used,
- can identify problems with mixing (if multi-component coatings were applied), and
- identifies the presence of additives, intentional or otherwise.
Of course, depending on the type of coating failure, the forensic analysis can reveal a multitude of other evidence, and may even eliminate or disprove initial thoughts on the cause of the failure. The laboratory component of failure investigation confirms or refutes opinions on failure mechanisms and can provide a means to recreate the failure mechanism(s). Without laboratory analyses, many opinions regarding the cause of failure are no more than suppositions. In litigation, the facts and an objective, science-based position should be the foundation of the case presented.
Clairvoyant Failure Investigations
An extremely severe case of reckless investigation exists when an opposing investigator has never observed the failure but discounts the findings of others and claims to identify the exact cause of failure and predict future performance. Under these situations, such an investigator relies almost entirely on discrediting the “opposing” report as a substitute for performing an investigation.
We have all heard that a picture is worth a thousand words. Similarly, witnessing and investigating the actual failure is also very important to having credibility. Reliance on another’s data, observations, and reporting requires a very restrained and thoughtful approach. A thorough understanding and unbiased interpretation of the available information is essential, and caution must be taken to assure that the investigator understands all of the facts in the opposing report. If not, significant mis-statements may be made.
While some statements made are a result of a lack of understanding of the coating failure, others may be deliberately deceptive because of a hidden agenda. Here’s an example: A failure investigation report discussed both field- and shop-applied epoxy. The first investigator determined that the shop-applied epoxy was performing well, showed excellent adhesion, and therefore required no remediation. The field-applied epoxy, on the other hand, was undergoing significant delamination and adhesion was poor in all locations investigated. Consequently, the investigator recommended replacement of the field-applied epoxy.
The opposing investigator, hired to rebut the report and never having seen the failure, reported that the findings were contradictory, and there was no justification to remove all of the field-applied coating. The “reviewer” simply extrapolated statements from the shop-applied epoxy evaluation (indication of sound coating adhesion) and transposed them next to the results of the field-applied epoxy evaluation (reported as having poor adhesion), thereby creating the impression of a contradiction. The original investigator pointed out the reviewer’s “mistake,” which ultimately cast doubt on the validity of the entire review.
Casting Doubt Using Unsubstantiated Statements
In some cases, the desire to disprove an investigation has been so strong that exaggerated statements were the only means used to cast doubt on the quality of the original investigation. An extreme example dealt with the criticism of a commonly used investigative ASTM laboratory test method. Replicate tests were performed on the same samples resulting in similar values. The reviewer proclaimed that performing the ASTM test procedure never results in repeatable findings. What the reviewer failed to note was that the results of the replicate testing fell well within the precision limits established by the standard test method. The reviewer’s statement (with no explanation), left it to the reader to conclude whether the unfounded proclamation was an error, a misunderstanding, or an intentional act to steer the reader away from the data generated. Regardless, the “opinion” was dispelled by reviewing the precision and bias section in the industry standard and by the fact that the standard is a common reference in many specifications.
Casting Doubt without Supporting Data
In a similar vein, some investigators are willing to make exaggerated statements even though there is no supporting data. One example involves an investigation in which a painter’s insurance policy was terminated 90 days after coating application. At some point after termination of the policy, a coating failure was reported to the insurance company that terminated the policy. Accordingly, it was important to determine if the coating failure occurred before the policy termination date to establish whether there was coverage for the company under the previously held policy. An investigator hired by the insurance company reported that without a doubt, the failure occurred exactly two weeks after the insurance policy termination date. The investigator chose to justify the opinion of the “likely” date of failure by performing accelerated weathering testing in a QUV chamber according to ASTM D4587, Standard Practice for Fluorescent UV-Condensation Exposures of Paint and Related Coatings.4 However, accelerated weathering exposure hours cannot be correlated to natural weathering exposure outcomes. The approach to establishing a date of failure and the statement declaring the time at which the failure occurred were totally inaccurate.
Extrapolating Coating Failures to Multiple Structures
Unfounded extrapolation is another pitfall to be aware of. Such was the case in a coating failure investigation on two small bridges assembled and coated in a shop. Heavy snow at the time of the site investigation limited access to only one of the two structures. The initial investigator found coating issues within certain isolated areas of the bridge (adjacent to main girder welds). These observations were extrapolated not only to the rest of that structure but to the second bridge, which was never examined because of restrictions on access. His recommendation: both bridges needed to be completely repainted. However, a follow-up and more thorough investigation of both structures by another party established that the coating problems were isolated to small areas (adjacent to the main girder welds) on one bridge. Ultimately, when the case went to mediation, the fabricator was required to repair only the areas around the welds on one bridge, not completely repaint both structures.
A fair and proper coating failure investigation requires a scientific approach, not one of preconceptions and deceptions. A qualified expert will carefully review all of the existing information and documentation without bias, conduct a thorough site investigation using appropriate tests and industry standards, engage in forensic laboratory analysis, and look at all of the field and laboratory evidence to formulate an opinion about the cause of the failure and the degree to which rework is necessary. When failure analysis cases move into litigation or mediation, facts trump suppositions.
- Journal of Protective Coatings & Linings, Volume 27 Issue No. 11 & 12.
- ASTM D6677, “Standard Test Method for Evaluating Adhesion by Knife” or Method A of ASTM D3359, “Standard Test Methods for Evaluating Adhesion by Tape.” Both tests are conducted by making an X-scribe in the paint film. The X-scribes are to be 1.5” long; cut using a straight edge and the two scribes are to intersect at a smaller angle between 30o and 45o. When using ASTM D3359, adhesive tape is applied to the scribe and rapidly pulled off of the surface upon itself. Adhesion is rated according to the amount of coating removed by the tape. When using ASTM D6677 the coating is lifted with the knife blade at the intersection of the incisions (without the use of tape). Adhesion is rated according to the difficulty of removal and the amount of coating removed by the knife blade.
- The cause of simple failures related to improper surface preparation or coating dry film thickness can be determined without laboratory testing. However, even in these cases, the laboratory testing can serve as a set of checks and balances on the field work.
- QUV testing is a cyclic condensation/heat-ultraviolet lightweathering procedure that involves intermittent exposure to UV light/heat and condensation. The test is accelerated and the ASTM standard definitively states that the test results cannot be directly correlated to natural weathering.
As Seen in The Journal Of Protective Coatings & Linings ©2012 Technology Publishing Company
Ray Tombaugh- Senior Consultant
Ray Tombaugh is a Senior Consultant for KTA where he has been employed for 10 years. He is a NACE Certified Coatings Inspector Level 3 (Peer Review) and an ASTM D4537 Level III Inspector with over 28 years in the protective coatings industry. In his current position, Ray provides coatings-related services (including coating failure analysis, coating assessments, specification preparation for paint and lead-based paint removal, laboratory and field paint testing, project management, and expert witness testimony) to a variety of clients with special expertise in the Water and Power industries.
Article Courtesy of JPCL “The Journal of Protective Coatings”
Photo by Walt Stoneburner