Coatings Selection Methodology
There are thousands of protective coatings on the market today for every type of structure and environment. To determine the correct coating chemistry and application method for each site-specific project, three representatives each play their part:
- The first person faced with this decision should be the specification writer.
- The next person faced with this decision should be the asset owner’s project engineer.
- The last person faced with this decision will be the coating contractor.
The Specification Writer
Step 1: Know the Structure
The first step for the specification writer is to become thoroughly familiar with the structure that will be protected by a coating system. He or she needs to understand all of the complexities of that structure and the level of corrosiveness it is likely to encounter throughout its design life.
Two good examples are the bilge area in a ship and the underside of the main deck on an offshore platform. Besides the corrosiveness of this environment, each of these areas will present challenges to the painting contractor by way of access and difficult-to-paint edges, bolts, angles, valves, flanges, etc. The specification writer must anticipate these difficulties and adjust his or her directions accordingly.
Step 2: Know the Fabrication Site
The second step for the specification writer is to become thoroughly familiar with the site where the fabrication and coatings application are likely to occur. He or she needs to understand the annual weather patterns for that site.
While epoxies are the most common corrosion preventative coating systems throughout the world, there are winter conditions in some of the major shipyards that can cause serious problems in applying other organic coatings, such as polyurethanes or polysiloxanes.
Step 3: Know the Applicator’s Level of Skill
The third step for the specification writer is to become thoroughly familiar with the skill level of the workforce at the proposed fabrication site. Of particular concern should be their skill levels with both conventional and airless spray systems, with special emphasis on plural component airless spray systems. (More on this later in this article.)
Owner’s Project Engineer
Step 1: Know the Specification
The first step for the project engineer is to become thoroughly familiar with the coating specification. Achieving the level of corrosion prevention intended in the specification becomes the project engineer’s responsibility as soon as he or she receives that specification.
The project engineer should know—from previous experience—the particular difficulties inherent in achieving the desired corrosion prevention with the chosen coating systems at the proposed fabrication site. If lacking such experience, the engineer needs to consult with others from the owner’s staff who are intimately familiar with the proposed structure and the proposed fabrication site.
An ounce of prevention is worth a pound of cure at this time. The specification writer may very well have been guided by the owner’s previous experience with coating systems on similar structures fabricated and/or installed in sites with drastically different weather patterns or workforce skill levels.
Step 2: Conduct a Pre-Job Conference
The second step for the project engineer is to arrange a pre-job conference with these representatives:
- The specification writer
- The project manager for the fabricator
- The project manager for the painting contractor
- A coating technical service manager
The purpose of this meeting is to go over the specification paragraph by paragraph, to make sure that the following is clearly understood by all parties. A technical service manager from the coating manufacturer favored by the owner should also attend. The project manager needs to leave this conference with the confidence that the specification for his/her project is truly “site-specific” to avoid unintended consequences, such as in this scenario:
- Inorganic zinc is specified but the workforce in the proposed fabrication site only has experience with organic zinc applied by airless spray. If that is the case, either the specification needs to be changed or a job-training program should be enforced to ensure that the specified coatings can be properly applied at this site.
- The specified organic coating system cannot be applied and cured below 40°F (5°C). If the proposed fabrication site is in an area where temperatures normally fall below this threshold from October to March, alternate coating systems will need to be approved before awarding the contract.
Step 3: Enlist Certified Coating Inspectors
The project engineer must ensure that qualified and experienced certified coating inspectors have been selected and assigned to this project. It is impossible for the project engineer to be on-site at all times during surface preparation and coatings application.
The selected coating inspectors must be completely familiar with the type of structure and the work procedures at the proposed fabrication site. They are the eyes and ears of the project engineer to ensure that the quality of the coating systems meets the owner’s expectations.
The Painting Contractor
Step 1: Know the Specification and Site Specifics
The first responsibility of the painting contractor is to read and understand the coating specification contained in the request for proposal (RFP) for this project at the proposed fabrication site. The contractor needs to be intimately familiar with:
- The proposed structure
- The proposed fabrication site
- The specified coating systems
- The annual weather patterns at this site
This information is necessary to determine what challenges this project will present in the way of equipment and labor skills, in order to meet the requirements of the specification.
Step 2: Select the Coating System
The second step for the painting contractor is to study the type of coating system specified for this project to make an informed decision on which manufacturer’s coating systems are most “user-friendly” at the proposed fabrication site during the proposed construction schedule.
The contractor needs to go into the pre-job conference with any suggestions for changes in the coating specification, based on which of the approved coating systems best fits the structure, the site weather patterns, and the skill of his or her labor force.
A good example is the choice of a 100% volume solids single-coat epoxy system for potable water tanks that will probably be coated during the summer part of the fabrication schedule. While this sounds great from a labor-savings standpoint, the requirement for pinhole-free application of such a system in Singapore or Dubai in the summer months presents a real challenge to applicators. The contractor should consider suggesting a traditional high-solids multicoat system that has a high rate of success at the proposed fabrication site.
The cost of the coatings should be the last factor in determining which of the approved coating systems the painting contractor purchases. The cost of the coatings rarely exceeds 10% of a coatings project, so the focus should be on equipment requirements, labor requirements, and potential production losses caused by tight limits on items such as pot life, induction times, and recoat windows.
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
Condition Survey - The Backbone of a Good Coating Specification
Defining Service Requirements & Environmental Factors for Coating Specification
Defining Client Objectives for Coatings Specification
Methods & Pitfalls in Selecting Coating Systems for 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