Fusion bonded epoxy (FBE) coatings protect the underlying metal from corrosion. The lack of research on the microbial impact of pipeline coating failures leaves a significant knowledge gap. We analyzed two FBE coating samples from buried steel transmission pipelines with unusually rapid external pitting.
In this paper, I will discuss such an example of when the predicted service of the coating determines that a more dynamic method must be utilized. I will discuss testing that was conducted for immersion service where flow of water over the surface was a major consideration. The question of how well the adhesion would hold up in real life service could not be properly answered by the degree of failure in this case. I discovered that the more important consideration was the survivability of the coating if a defect were introduced.
Often when a polymer coating failure occurs, the concrete quality and integrity are questioned. Core samples removed from the concrete slab are examined using petrographic techniques to help determine the cause of the coating failure. The basics of the petrographic examination, the equipment used and what information it can provide are presented.
When establishing the minimum conditions suitable for coating concrete, many coating manufacturers, and hence specifying engineers and contractors, generally rely on unrealistic moisture content and moisture vapor emission rate requirements. These compulsory values are founded on laboratory testing rather than field experience, or worse still, on supposition rooted in unachievable and unrelated requisites.
This paper presents the diagnostic work undertaken to determine the cause of failing coating and spalling block on the exterior of a commercial building in northern Illinois. The field assessment methods used to diagnose the problems including non-destructive and destructive methods for determining moisture content in the masonry, infrared thermography, and visual assessments are described.
Coatings are a composite blend of raw ingredients that are mixed, applied to a prepared substrate, and dried and cured correctly to perform to their maximum capability. Failures and defects can appear themselves at numerous times in the life of a coating. Prior to application, they can take the shape of settlement and skinning, during application as runs and sags, shortly after application as solvent popping and orange peel, and during service as blistering and rust spotting. Therefore, it is not unexpected that those coatings can suffer from premature failure and/or exhibit defects that may or may not result in failure. Coatings nowadays are the most efficient method to shield metals and thus has been widely engaged among various protective techniques 1, 2.
Industrial and marine protective coating systems are most commonly applied without incident and perform as expected over their anticipated service life. However, occasionally, a coating system will fail prematurely, for unexpected reasons, and with expensive consequences. This paper addresses those unexpected failures and provides reasons and remedies for such occurrences.
The United States Army and Marine Corps (USMC) paint their vehicles with the Chemical Agent Resistant Coating (CARC) system. This system consists of a pretreatment, an epoxy primer, and polyurethane topcoat, similar to many other industrial paint systems, but with added functional requirements (e.g., chemical agent resistance, camouflage, and signature reduction) unique to these paints. The systems that utilize these coatings are also designed for specific capabilities, of which corrosion is usually a lower priority. Lastly, the vehicles and equipment of the Army and USMC typically operate in harsh environments, which are highly corrosive.
While commercial painting is often thought to be less rigorous or less technical than industrial painting, the commercial painting industry has its own set of demands on a coating and is not without its share of coating problems. The authors experience demonstrates that there are commonalities in failures of coatings in commercial painting.
Galvanized mast arms support uncounted numbers of traffic signals and signage throughout the United States. The proportion of these that have a “duplex” coating system (both galvanizing and organic coatings) is unknown. However, the number is surely significant, and the number of coating system failures is also significant.
This paper will describe this commonplace corrosion problem associated with protective coating damage at dissimilar metal bolted connections and present a typical case history. The paper will go on to explain why slotted bolt holes are more susceptible to more aggressive corrosion damage than round bolt holes. In addition, the paper will present successful measures that can be taken to prevent this prevalent problem.