Methods & Pitfalls in Selecting Coating Systems for Specification
Specifying coating systems for either industrial or marine projects requires a detailed process that results in coating systems that meet the requirements of the owner on each specific project.
Writing an effective coating specification can be relatively simple or quite difficult, depending on the type and size of the structure to which the coating systems will be applied. The coating specifier has several ways to approach this decision-making process. Following are three widely used approaches.
1. The Legacy Approach
Select a coating system that has a long history of success on similar structures. Provided that the legacy coating system has not undergone significant changes in formula due to changes in environmental regulations, this approach has a high degree of potential for success.
2. The Comparative Testing Approach
Select several coating systems that appear to have the performance properties needed on a specific project. Test them side-by-side on laboratory test equipment and test methods designed to duplicate as much as possible the aggressive attack on these coating systems that is expected in the intended service environment for a specific project. (For more on this topic, read Defining Service Requirements & Environmental Factors for Coating Specification.)
This approach can also be quite successful, such as in testing pipeline coatings. However, designing a test procedure—that accurately duplicates actual project conditions for complicated structures that will serve in environments that change significantly with seasons of the year—can be extremely difficult. Comparative testing gives the specifier a degree of confidence that the coating system will work, but changes in site conditions might render the test procedure useless.
3. The Manufacturer’s Coating System Recommendations Approach
This approach is widely used in the marine industry because the coatings used on various areas of a ship can be surveyed periodically during the ship’s life. With this inventory of successful performance, the manufacturers are ever-ready to present the specifying engineer with a basic blueprint for the entire ship along with voluminous case histories of successful usage.
While this approach is very common in the marine industry, it is less common on complicated industrial structures where the site conditions can vary greatly compared to the site conditions of a marine newbuilding project.
Some Common Pitfalls and Considerations to Keep in Mind when Selecting a Coating System
There are many factors and pitfalls that can impact the success of a selected coating system, regardless of the approach used by the specifier. These include several requirements that the specifier must verify or perform on his or her own.
- Requirements vary broadly in different parts of the world.
Just because a coating specifier has succeeded with a refinery project in the USA does not automatically mean success with the same specification on a refinery project in another country. Site conditions vary widely, applicator skills vary widely, and governmental worker health and safety regulations vary widely. (Recommended reading: Writing Safety Into Your Coating Specification.)
- The quality of raw materials can vary depending on where a coating is manufactured.
There is also variance in qualifications of local coatings manufacturing sites. While global-scale manufacturers go to great expense to formulate coatings that are intended to be the same in all plants where a coating is manufactured, some key raw materials may not be available at all these plant sites.
For example, a simple change in the quality of titanium dioxide can render a perfectly good formula useless because the locally available grade of titanium dioxide does not have the same resistance to ultraviolet attack and the finished coating leaves the fabrication site meeting all required tests, yet fails when the coated structure is stored outside in hot, humid weather for several weeks or months before being installed.
- Be totally knowledgeable about the owner’s philosophy towards the project.
Is the asset owner’s decision-making process based predominantly on Acquired Cost, or is the owner willing to consider cost per square foot/meter per years of service? There have been several studies published that have stated clearly that the lowest acquired cost (cheapest) coating systems are often more expensive over the life of a structure.
The coating specifier must know his/her owner’s philosophy before he/she commits to the task of writing a detailed specification for an entire project. One thing is certain: the larger the scope of the project, the more attempts there will be on the part of the fabricators to use local, lower-cost coatings that are presented as “equal to” the coatings in the actual specification.
Unless the specifier is certain that the owner will resist these cost-cutting attempts, his/her work is doomed to achieve less than desired results.
- Beware the contractor’s change order requests.
It is not unusual for fabricators to submit exorbitant change order requests based on having to apply the specified coating systems, rather than what they bid in the first place. Despite the fact that the original bid was requested on the basis of the coating system included in the bid documents, unless the owner is committed to the original specification, either equipment, application or coatings changes will be included to try to justify the change order request.
Bottom line: The most important statement that a specification writer should be able to make about his or her work is this: “I have written this coating specification, for this structure, in this location, in this ambient condition.”
Specifying coating systems for either industrial or marine projects requires a detailed process that results in coating systems that meet the requirements of the owner on each specific project. There is no universal template that can possibly cover the vagaries of each project.
More in the "How to Write a Great Coating Specification" series:
Coatings Specifications, Good, Bad or Ugly: Lou Vincent Q&A
Why it’s a Mistake to Reuse Old Coating Specs: Lou Vincent Q&A
Who Participates in Selecting Equal Coating Products?
Condition Survey - The Backbone of a Good Coating Specification
Defining Service Requirements & Environmental Factors for Coating Specification
Defining Client Objectives for Coatings Specification
Tightrope: Identifying Limiting Conditions for Coatings Specification
Problems Caused by the Lack of Clarity & Definition in Coating Specifications
Writing Safety Into Your Coating Specification
Written by Louis D. Vincent | Owner, L.D. “Lou” Vincent PHD LLC
Renowned corrosion-industry author and teacher, Lou Vincent has 57 years’ experience in the coatings industry. Lou co-authored the third edition of “Corrosion Prevention by Protective Coatings,” by Charles G. Munger, and authored “The Protective Coatings User’s Handbook” and “The Marine Coating User’s Handbook,” reference manuals that have influenced corrosion professionals for decades.