When young professionals enter the corrosion coatings industry, it can be both intimidating and confusing. As they meet more people in the industry, they appreciate the fact that the skill sets for a successful career are varied, and nobody jumps seamlessly between all of them. Some of the more meaningful, and often surprising, things about coatings and the people who use them will follow.
Coatings Failures
When first starting in the industry, one hears a lot of anecdotal information about coating failures, because failures make for a better story than successes. Stating that a coating was “coming off in sheets” conjures up a mental picture of huge slabs falling off the steel.
However, just as all politics are local, a similar situation exists for all coatings failures. Coatings don’t fail by simultaneous massive disbondment; they mostly initiate in local areas of either weakness, such as edges and welds, or in spots where the surface preparation was substandard.
Most of the problems that the industry has with coating performance have little to do with use of substandard products, bad specifications, or applicator apathy. The industry is overwhelmingly using quality products and specifications, along with skilled applicators and inspectors.
This, however, is only part of the implementation of a successful coatings life cycle. Other problems can ruin a coatings program: among the most prevalent are missed inspection points, weather changes, at least one under-trained applicator, failure to prioritize repairs, and cost cutting. The best that can be expected is to start with the best products and personnel to limit problems later—don’t expect zero defects, but give the project the best probability for success.
In addition, most coatings failures have some type of defect as their origin (see Figure 1). These failures are quite often surface preparation or application-related, such as a location that is difficult to coat or repair.
Knowing this, all quality coatings should have some inherent surface preparation and application forgiveness built in, because flawless prep and application is not a reasonable industrial expectation.
Coating Thickness
Too many people maintain the philosophy that when it comes to applied thickness, “more is better.” Another expression is “coat thin to win.” Which is closer to the truth? There are examples (see Figure 2) where under-thickness and over-thickness each pose separate coating integrity problems.
Thicker coatings are usually better barriers. But with thicker coatings, two issues present themselves: 1) the internal stresses within the coating can cause problems as the coating contracts/expands while curing and in service, and 2) the coating is slave to the flexing of the object being coated, whether the flexing occurs during shipping, construction, or in service.
Clearly, the optimum thickness for coating performance is dependent on the coatings system used. One expert postulated, from personal experience, that “a little thicker is a lot better.” The balance between avoiding defects while limiting the internal stress in the coatings system is key to optimizing coating thickness.
FIGURE 2 (a) Under-thickness on a thermal spray aluminum (TSA) coating results in a porous film and lack of corrosion protection, and (b) overly thick abrasion resistant overcoat on a pipeline, resulting in cracking and shear disbondment after slight bending.
Life Prediction and Testing
The first request a young coating specialist might hear from a customer is to provide some assurance that the coating they are recommending will meet the design life of the facility.
Given the multiple corrosion models and predictive tests within NACE/Association for Materials Protection and Performance (AMPP) publications, it seems reasonable to expect similar testing to be available for protective coatings. Despite what the “experts” may say, there is currently no accurate life prediction testing for coatings, just tools for relative rankings.
How were these tools developed? Extrapolations of common quality control (QC) tests for application, with the assistance of industry expert opinions to set pass/fail criteria. Examples are salt fog and ultraviolet (UV) chamber exposures, cathodic disbondment tests, atlas cells for internal linings, and miscellaneous retained property tests after an exposure.
A number of experts have shown data about the performance of atmospheric coatings in the standard qualification tests vs. field site natural weathering vs. actual facility performance. There is usually very little correlation among these three data sets.
Some of is related to the difference in surface preparation and application among these three cases. Another is that the actual destructive forces against the coating in qualification testing is controlled, in natural weathering is measured but not controlled, and in service is dependent on the local microclimate within the facility.
So are these coatings formulated for short-term, medium-term, or long-term performance? The answer is, sadly, for short-term performance, for the simple reason that the coatings must pass the QC-type tests to gain any industry acceptance.
While formulators hope there is a correlation between these tests and long-term performance, anecdotal evidence suggests that this is not possible to quantify.
Generally speaking, the end user must select coatings that perform well in any tests that they deem relevant and assume that their odds for long-term success have improved.
Coating Product Numbering
A daunting task for a young coatings specialist is to make sense of the myriad of seemingly identical products available from any given coatings supplier. How can one company sell five different epoxy phenolic tank linings, all of which say essentially the same thing on the product data sheet? And when one hears about a product name and number, is there an industry convention that could provide info on that coating just by how it is named?
The truth is, while there may be some intra-company conventions used by some coatings manufacturers, those conventions are limited to that individual company.
There are some consistencies across names—for instance, the “-thane” suffix is always a polyurethane product, and “-zinc” is used by many for various zinc-based products. But as for the numbers, good luck. One cannot determine the characteristics of a product by the name and number alone.
Why do coatings suppliers offer multiple versions of the same product? The answer: Simple branding. Once a product is on an approved list, to discontinue the product simply because of a “new and improved” version would likely mean a decrease in sales. Some user coating specifications and acceptable product lists live on for 20-plus years without revision.
Therefore, keeping a product alive makes economic sense, even if the product is only produced for one or two customers. Just dig up the formulation and batch a few gallons to keep the customer satisfied. This results in product catalogs that look like a dictionary, but really, only a handful of products in the catalog will be of use to a particular customer (see Figure 3).
FIGURE 3 The total product catalog vs. one containing only products of interest to the user.
Lawyers and Contracts
Coatings specialists and legal experts often see the world a bit differently, but they both have a role in coatings projects.
When a normally rational, logical coating expert takes an action that is technically incorrect and defies logic, there is a likely legal/contractual reason behind it. Examples include adhering to a nonsensical clause in a specification or rejecting a win-win compromise. It is difficult, as a young specialist, to sense that something else is going on besides normal technical reviews.
The primary responsibility of lawyers and contract managers is to protect their company, not to understand the implications of their work on the progress of a technical project.
This is sometimes difficult to accept as a coatings specialist. The best that one can hope for is that these people will use some logic and understand when taking a hard line on a legal position is not necessary.
Coatings Experts
At what stage of a coatings career can people consider themselves coatings “experts”? Some get overconfident after a few “wins,” while others spend their whole career in fear of being discovered as a fraud.
The truth is one should never think of themselves as an expert in all things related to coatings. Several vastly different perspectives are required for execution of successful coatings programs. People working coating projects can be divided into at least three groups:
- Those who think about polymer chains in the coating, corrosion mechanisms, lab tests, and results interpretation.
- Those who thoroughly know the specifications, codes, and referenced standards, data collection needs, and pass/fail criteria.
- The construction and execution people on a coating project who consider scaffolding challenges, compressor sizes, weather windows, safety policies, and scheduling.
For the question of when a coatings specialist becomes a coatings expert, there is no magical transition. When senior coatings experts stop disagreeing or correcting them on coating matters, that means a specialist is on track to becoming an expert.
Coatings Decision-Making
While some spirited discussions and arguments will occur at AMPP technical conferences, true technical experts rarely disagree on the fundamentals of coatings. While some differences in personal experiences may exist, coating experts will carry the flag of their employer and defend their own company practices.
Most serious coatings service problems are the result of decisions to “optimize” application and maintenance. Common sources of problems include lack of inspection, rushing facilities back into service, and continually deferring coating repair and maintenance.
Planners may use risk-based work selection practices to set budgets and schedules, and often coatings maintenance is deferred since a “just wait another year” philosophy is hard to resist when something has to be sacrificed.
Figure 4 is an example of an offshore structure that continuously deferred coating maintenance until major repairs were required.
FIGURE 4 Offshore (a) deck plating, showing through-hole corrosion due to failed non-skid product, and (b) structural beams with severe metal loss after 15 years of service and inadequate coating repairs.
Technical Stockholm Syndrome
Stockholm syndrome is a psychological phenomenon that occurs in situations in which a hostage begins to feel sympathetic toward their captor’s cause, or a kidnapping victim falls in love with their kidnapper. Technical Stockholm syndrome is the belief that the technical field in which one works is superior to competitive technologies. One falls in love with their own work and loses objectivity.
Coatings are not always the best solution for corrosion control. Other options exist, such as chemical treatment, cathodic protection, corrosion-resistant alloys (CRA), and plastics/composite. None of these options are always best, but Technical Stockholm syndrome exists in all of these technical areas. The alloy metallurgist will believe that CRA is the superior solution, the chemical treatment specialist jumps to the chemical answer, and so on.
A young coatings specialist will feel frustrated when a room full of diverse experts does not concur that coatings are the solution for the problem. How does one make the case for coatings when faced with other experts? The others may not acknowledge their own prejudices, their own case of Technical Stockholm syndrome.
The best a coatings specialist can do is have answers and data at the ready for discussion and fully acknowledge the risks that come with the use of coatings.
When looking at any technical corrosion challenge, one must realize that all engineering decisions, at some level, come down to money. The solution with the lowest life-cycle cost, with acceptable risk, is usually the correct decision. Multiple factors play a role in these decisions—price, delivery time, supply chain logistics, contracts, even public relations (e.g., “local content” laws).
One example of a technology that is not as widely used as logic might dictate is thermal spray aluminum (TSA). Properly applied TSA is impervious to water permeation, ultraviolet radiation, and disbondment, offering durable corrosion protection. However, TSA is costlier than organic coating, is a slower process, requires skilled applicators, and uses specialty equipment that doesn’t lend itself to all projects.
A young specialist must recognize where certain coating solutions truly make sense and pick their spots to champion these coating technologies.
Final Thoughts
As the Greek philosopher Socrates once said, “Wisdom comes with the gradual discovery of our own ignorance.” Good coatings specialists constantly discover things they didn’t know previously. One never stops learning.
Eventually, specialists gain experience and might be surprised that they can teach things to senior experts. When an “expert” states a “fact” that clearly is wrong, the observer will see that the expert may not follow the teachings of Socrates. To which we apply a corollary to that quote: “Confidence is the discovery of everyone else’s ignorance!”
Editor’s note: This article first appeared in the January 2025 print issue of Materials Performance (MP) Magazine. Reprinted with permission.
