Even the smallest of coating failure areas can result in corrosion, weaken a structure, and eventually lead to catastrophic failure. Because coating failures—such as corrosion, deterioration, and loosening adhesive coats—include huge repair costs and lengthy downtime, engineers and chemists strive to examine the causes of failures to circumvent added expenses.
Coating-related failure is a complex subject. As a result, recognizing the underlying causes of a failure isn’t a simple task, especially since these incidents involve a combination of mechanical and environmental determinants. It is essential to evaluate coating failures’ main reasons to measure financial responsibility and understand the fundamental problems. Therefore, it is imperative to have a detailed understanding of the frequently encountered failures, reasons for their occurrence, and potential remedial actions to deal with coating failures efficiently.
What is Coating Failure?
Coating failure can be explained as the loss or reduction of a coating’s bond strength between coats and the substrate. Premature coating failure happens before the expiration of a coating’s potential lifespan, while catastrophic coating failure is extremely abrupt, terribly dramatic, and very severe. When failure occurs, some action is required to revive the coating’s properties to the level necessary for it to function as intended.
How Coating Failure Happens
Coating failure happens when a protective coating fails to protect the substrate, provides an aesthetic look, or serves some other intended purpose. A typical coating system functions in many ways, often acting as a waterproof barrier, providing strong adherence with the substrate, keeping the cohesive and adhesive integrity of film throughout its service life, and resisting atmospheric and chemical deterioration. The period during which the coating can be relied upon to retain its bond strength through all varieties of stress and strain is determined by the strength of the initial adhesion of the coating with the substrate and the conditions to which it is exposed. The initiation of coating failure is often slow, but once started, it propagates swiftly, thereby defeating the very purpose of using an expensive coating system.
There are various forms of coating failure, most of which are marked by coating detachment. Coating failures can also transpire throughout the application, curing stage, or post-application. Statistics suggest that the bulk of coating failures are a result of inadequate surface preparation and application. Typically, the failure takes place for a combination of reasons that need expert examination.
The Consequences of Coating Failure
Coating failures can transpire due to basic formulation design, incorrect system spec, poor surface preparation, improper administration, and environmental stress factors. Coating failure involves various kinds of coating defects with varying levels of impact on the general coating life. One of the real problems with coating failures is that they typically seem relatively innocuous from the surface, while monitoring the substrate beneath can reveal significant corrosion defects.
The guilt for coating failures is often placed on coating materials. The bulk of failures occur in applications wherever specifications for surface preparation, undercoating, or coating application haven’t been developed or are not followed. For example, improper or incomplete cleansing and removal of rust, mildew, abrasive or different surface contamination will result in the poor adhesion of a coating to a metal surface. An inadequate surface profile will also limit the utility of an ordinarily good coating system. Coating failure often occurs when there’s insufficient curing between coats and the improper mixing of multi-component methods. All such potential contributory factors must be analyzed to determine the causes and mechanisms of a coating failure. Background data on the history of coating systems, application methods, service atmosphere, and physical and instrumental characterizations of the failed coating are necessary for identifying the right causes of such failures.
Coating failures might end in serious corrosion and operation issues with financial losses. Also, repairing a damaged coating is often a very hazardous and complicated process. For example, several oil and gas projects have suffered tremendous losses attributed to paints and coatings’ premature failures, including the massive natural-gas explosion that occurred in Sweet Water, Alabama, in December 2011. The expenses to remedy such failures far outweigh the initial cost of coating. The cost of having to shut down can also be high. Of course, in situations such as this one, where a pipeline is transporting dangerous goods, serious liability is also a major concern.
Common Forms of Coating Failure and How to Prevent Them
Several common methods of coating failures and ways to prevent them are indicated below:
A dusty material indicates chalking on the exterior of the coating. Using a coating with better UV resistance can reduce chalking.
Erosion refers to the elimination of a coating by association with environmental components. Reformulation or choice of substitute materials with greater hardness ought to reduce erosional effects.
Blistering is the development of little to large, broken or unbroken bubbles underneath or inside a coating. Greater attention to surface preparation can help eliminate contamination and enhance adhesion between the coating—and therefore the substrate—to reduce blistering.
Orange peeling refers to the development of hills and valleys on the coated layer resembling an orange peel. It can be eliminated by adjusting coating conditions or solvents and removing them by sanding and applying another coating layer.
Pin-holing refers to little holes on a coating surface that provides a path of exposure to the substrate. It often arises due to improper spray atomization and can be reduced by coating the system more than once.
Undercutting occurs when corrosion byproducts from the substrate under the coating cause the coat to rupture. This can be decreased by increasing coating/substrate adhesion and using an inhibitive primer on the substrate before implementing the prime coat.
Cutting Coating Costs
Avoiding coating failures is essential in virtually any engineering application. The most frequent causes of coating failures include inadequate specifications, poorly prepared substrates, inappropriate application, untrained personnel, and dangerous construction methods. Failure, once it has occurred, can be corrected by deploying appropriate remedial measures. However, this method will be cumbersome, time-consuming, and expensive. Prevention is always a better remedy.