Manufacturers within the protective coatings and linings industry recognize that an unacceptably high percentage of the projects, to which we supply our products, fail prematurely. Generally, the industry is fully aware and agrees that the primary reason for this depressing statistic is that many of these applications are carried out under less than ideal conditions. Projects often suffer from inadequate/incorrect surface preparation and coating application.
Most protective coatings and linings manufacturers would agree it is becoming increasingly unlikely that these failures can be attributed to "bad" product. Due, in part, to the vast experience gained in product formulation, coupled with the extensive product performance data gathered, it would appear that many of these coating failures can be attributed to one thing – the application. (Quality control during the application is discussed in Increasing Coating Performance through Application Process Control.)
Teamwork Begins with Coating Product Testing
Conscientious manufacturers subject their products to rigorous testing protocols before they even think about releasing them to the industry. Once this test regime is completed, most then release the products for field trials.
This first step ensures that, as far as possible, laboratory testing is corroborated by performance testing on real-world equipment. Only then would a new product be released for sale within the relevant market sector.
However, in the interests of impartiality, there are many examples in industry where these protocols have not been adhered to, for one reason or another. In cases of this nature, the product in question has been swiftly withdrawn from sale until the problem has been eliminated.
Further to this, many potential clients have developed their own inventory of stringent "product acceptance test criteria," which must be passed if products are to be included within a client's "Coatings and Linings Specifications." This document details where and when commercially available products can be used.
Figure 1. Laboratory testing of atlas cells.
Taking all of this into consideration, it is fair to assume that the cause of premature in-service failures of modern protective coatings is unlikely to be a product problem. As already agreed by most, it is more likely to be associated with the application method of that product, or a correct application procedure carried out under less than ideal conditions.
For most within the industry, this conclusion is not a revelation. In fact, it is a cause that has been championed by numerous scholarly and technical bodies for many years now – including NACE, SSPC, ISO and ASTM, to name but a few. All of these institutions continue to work tirelessly to promote the principle that the correct application of any coating or lining is fundamental to ensuring an acceptable and economical system service life.
Yet the risks still remain. What needs to be done to minimize the risk of premature coating failure and maximize the performance life of the applied coating? The answer to this question is not an easy one. If it were, then it would probably have already happened!
Maximizing Coating Life and Minimizing Failure Risk
In order to achieve the ultimate goal of minimal risk and maximum life for any coating project, several factors need to be taken into account, and all of them must work in synergy for the desired outcome to be realized. There are five main factors that, in the author's opinion, can have an adverse effect on the quality and longevity of any coating project:
- Equipment design
- Application environment and coatings inspection
- Faulty specifications
- Application contractor experience
- Client expectations and misconceptions
- Coating characteristics
In this article, we cover the first three factors in the list above. (The remaining three factors are discussed in Common Misconceptions That Contribute to Premature Coating Failures.)
How Process Vessel Design Contributes to Coating Failures
Until recently, the experience of most industry professionals was that process vessel designers did not automatically accept that the equipment they design might need to have a protective coating. Either this includes internal linings or external coatings applied when new or at some stage during a tank’s operational life.
Indeed, opinions may even indicate that since most Design Engineer training has its roots firmly embedded in metallurgy, some would dismiss the use of internal linings from the outset. Instead, they would prefer to use ever more complex corrosion and erosion resistant metal alloys and alloy overlays. However, due to availability and economic constraints, alongside in-service experience, this trend is now beginning to decline.
Figure 2. Process vessel shapes can prove difficult to coat and inspect.
Occasionally, manufacturers, and more importantly lining applicators, can be confronted with process vessels that were not designed with lining application in mind. Some common examples of poor design include:
- Baffle plates too close together
- Sumps that are too deep for an applicator’s arm to reach
- Welded internal furniture, making access to sections of the vessel virtually impossible
- Small bore nozzles and nozzles that twist and turn in a multitude of directions
The list goes on. (Be sure to read Best Practices in Installing Process Vessel Lining Systems for more on this topic.) However, clients are now beginning to realize that organic linings are, if correctly installed, a viable alternative to expensive exotic alloys. In fact, they are beginning to instruct design houses, up front, that a lining will be considered as an option for corrosion protection and that any design should take this into consideration.
This design directive indicates that the use of an organic lining solution must become an integral part of the vessel design and delivery, requiring its own dedicated management and maintenance regimes. Any hope of making this corrosion management solution a successful and economically viable part of the equipment’s life cycle costs is dependent upon this directive.
Despite many asset owners and operators beginning to understand the concept, coatings and linings manufacturers must still impress that successful application and operation of any lining begins with equipment design.
The Role of the Coatings Inspector
Although the mechanisms of environmental cause and effect are fully understood, they still need to be correctly considered and acted upon in order to maximize the service life of the coating or lining. It is now generally understood and accepted that the environment prevailing during any application will have an effect upon the outcome of that application.
Therefore, the responsibility for applying the correct environmental controls is usually allocated to the coatings inspector. In fact, most projects would utilize the services of at least one fully qualified professional.
Coating inspectors are qualified and certified by the industry, for the industry, and are in essence quality control technicians. Unfortunately, if you ask clients, project managers or contractors what the role of the coating inspector is, you would be surprised at the many and varied answers you are given.
Many clients assume that if there is a coating inspector on site, then all will be well – and if it is not, then the inspector must be responsible. Contractors generally look upon the Inspector with suspicion and distrust, convinced he is there to make them do more than is actually required and losing them their profits in the process.
In reality, the responsibilities of the coating inspector are to ensure that, under prevailing circumstances, the application is carried out in accordance with a written and agreed-upon coating specification document. It is their responsibility to carry out specific testing in agreement with a quality control plan (QCP), in order to verify that the conditions itemized within the coating specification have been observed as far as possible. At the very minimum, they are there to observe, measure, document and report. Overall, a good inspector will accomplish this in a completely unbiased fashion.
The coating inspector is a necessary requirement in order to minimize risk as much as is practically and economically possible. It is generally agreed that the coating inspector is a vital cog in the coatings application machine, without which the chances of success are less than optimum. However this latter statement, of course, assumes that the specification, often written by the client, is adequate for the application in hand and is not merely generic in nature. It also assumes that the application contractor can actually undertake the work in accordance with it.
Unfortunately, many coatings and linings specifications do not take into account the specifics of the application at hand, or the site-specific environment in which the application is to be undertaken. Many are written without any knowledge of the project location, the product requirements or the application situation – and this is where conflicts begin to occur. (Learn more about faulty specifications in the article Problems Caused by the Lack of Clarity and Definition in Coating Specifications.)
Discrepancies between reality and the specification document can cause contractors to incorrectly price applications, based upon the specification document, before realizing that they cannot deliver what is required. Coating inspectors adhering to the specification then come into conflict with the contractor, who cannot comply because of additions to the original quotation.
This scenario happens all too often during the lining application phase of a project. But with a small amount of cooperation, application risks can be minimized by organizing a "pre-start meeting."
By involving all parties, the specification and subsequent changes can be agreed, dependent upon the prevailing environmental conditions and location of the work site. Additionally, each party can be apprised, via the pre-start meeting minutes, of their agreed individual roles, authority and responsibilities.
Together, Everyone Achieves More
Clearly, for coatings and linings to become a viable, long-term solution to the damaging effects of erosion and corrosion within the industry, it is vital for everyone involved to work together. (See how the selection of suitable coatings can minimize surface damage in Erosion Corrosion: Coatings and Other Preventive Measures.)
Currently, projects begin with an idea. This idea evolves into a design that, if accepted, will be fabricated and coated, if required. At this point, contractors will be supplied with a specification and asked to bid for the coating work. Often in the case of new build, this means the site is unseen. At no point do all of the parties involved get together to discuss the project.
In the technological world we live in today, shouldn't this be possible? Certainly, it is more possible than it was before the advent of the Internet and its channels of communication.
Ideally the client, lining manufacturer and design authority need to be in communication from the outset so that a suitable and compatible design and lining combination can be agreed upon. As soon as possible, the chosen lining manufacturer should be able to liaise with the fabricators and recommend trained reliable contractors to bid for the application of their product.
Lastly, as soon as it is possible, all parties should meet to discuss the application method statement, quality control plan, and specification. If this comprehensive teamwork is achieved, we truly say that risk has been minimized and that the applied lining has been given the best possible opportunity to give optimum performance.