CoatingsPro Magazine

NOV 2017

CoatingsPro offers an in-depth look at coatings based on case studies, successful business operation, new products, industry news, and the safe and profitable use of coatings and equipment.

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Page 49 of 60

COATINGSPRO NOVEMBER 2017 49 To call a failure a failure, the performance requirements for the paint or coating system must be defined before application. is may include life duration and maximum limits for defects of the coating systems. is information should be contained in the protective coating work contract and specification. Any warranty associ- ated with the protective coating work should also contain the definition of "protective coating failure" related to the particular project. For example, if a coating system applied to the steel support beams of a bridge has a warranty to last 15 years, it should last at least that long. If the coating starts to flake off of the steel after only one year in service, this is what we would consider a premature coating failure. W hen an analysis is completed, there are generally about nine steps that the investigator should follow to get to the bottom of the failure. It is normal practice in the coating and lining contracting industry, when a problem occurs, to dump the failure analysis onto the inspector, owner, coating manufacturer, or some combi- nation thereof. I recommend that the coating/lining contractor also conduct its own organized failure analysis following the nine steps that I have identified in this article to develop an informed opinion as to what actually went wrong and thus be in an informed position to expeditiously and econom- ically resolve the problem without protracted arguments and/or litigation. 1. Define the Failure e key to this step is to succinctly characterize the failure of the coating system. e failure must be correctly and accurately described using ASTM standards, jobsite photos, etc. Of particular value in this effort is the training afforded to the inspectors, such as the NACE Coating Inspector Programs CIP-1 and CIP-2. ese two courses in particular train people in clear and accurate documentation of protective coating failures. 2. Complete Interviews and Records Examination To understand a coating failure, it is necessary to review all available records and, if possible, interview personnel who were originally involved with the selection and application of the coating system. Often, little or no documentation is available related to protective coatings that have failed, so interviews with personnel involved can be invaluable. Information that should be assem- bled includes: 1. Product data sheets for coating materials (Note: Make sure that you have the edition of the product data sheets that were in effect when the products were mixed and applied; product data sheets can be signifi- cantly revised over time!); 2. Coating work records; 3. Nonconformance reports; 4. Start and end dates of coating work; 5. Temperature, humidity, and weather data; and 6. Information from coating manufac- turers concerning coating material formulation changes made since the coating application was performed. 3. Specification Review Job coating application specifi- cations for the protective coating system involved should be reviewed. e surface prep, coatings, and atmosphere conditions specified should all be recorded. Note: e dates of documentation reviewed should align with actual protective coating work whenever possible! Remember that protective coating application specifica- tions are revised over time, and a recent revision to a specification may not accurately represent the requirements in place when the failed protective coatings were applied in the past. 4. Field Observations After review of available documen- tation and personnel interviews, the contractor's failure analyst should perform close-up examination of the protective coating failure — both general environment and close-up observations. First, he or she should carefully analyze the environment of the failure site and identify any poten- tial effects on the failure. en, he or she should perform nondestructive and destructive examinations of the failed and intact coating system as appropri- ate. is would include destructive and nondestructive tests, such as micro- scopic examination, adhesion tests, solvent rub tests, "tap tests," etc. Subsequent laboratory examina- tions of the failed coatings may be required, so the inspector and contrac- tor should be prepared for there to be samples sent to a lab. 5. Laboratory Examinations If the inspector determines that labora- tory tests are necessary to support the protective coating failure analysis effort, the following are tests that can be performed by knowledgeable coatings laboratories to contribute to and support the failure analysis effort. A. Optical and Digital Microscopy • 30X–200X works well in most cases • Can be used to determine number of coats comprising a system and relative thicknesses of each coat • Often contaminants are visible (such as mill scale, dirt, overspray, and salts) • Small cracks, voids, inclusions, etc., can be observed B. Gas Chromatography (GC) • Used to examine relatively volatile A "failure" is defined as a deterioration occurring before the anticipated time frame. Failure Analysis 101

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