What is a coating specification?
A coating specification serves several purposes. At its most basic it’s a plan for how a coating will be applied by the applicator company. It may refer to any number of international standards concerning preparation and application of the actual paint or powder coating. A coating specification can even provide guidance on how the customer or client is advised to look after the coating once the parts have been installed. This all assumes that the specification for the coatings is appropriate to meet the expectations of the final owner of the coated parts.
Quite often it is the case that coating specifications are poorly written, with room for ambiguity built in and failing to account for factors that could easily lead to problems in application or longevity of coating service.
There are two common aspects to a coating specification; ‘Performance-Based’ requirements and ‘Specific Named Products’ requirements.
Performance-Based Specifications
As the name suggests, a performance-based specification provides a list of performance requirements of the coating as applied and cured. These are the minimum, not as some might like to think nominal or average, requirements. These types of specifications will often reference other independent specifications such as SSPC (Society for Protective Coatings) or NACE (National Association of Corrosion Engineers) or others.
A well-crafted coating specification will address specific requirements of the project. For example, it may reference ASTM B117 (often referred to as a Salt Fog Test). The coating performance specification will provide far more useful results by going further than simply making reference to the standard, it would be best to detail the extent of the test and the minimum requirements (such as 500 hours salt ascetic, no blistering or corrosion creep more than 5 mm). Any coating system can be tested, but without a specified performance requirement the test is meaningless, worse it adds cost without providing any benefit.
Some Commonly Used Tests
| Performance Requirement | Test Method | Example Performance Requirement |
| Corrosion Resistance by Salt Fog | ASTM B117 | ≤ 5 mm UC after 500 hours |
| Corrosion Resistance by QUV-A | ASTM D5894 | ≤ 5 mm UC after 3000 hours |
| Weathering by QUV-A | ASTM G53 | 75% Gloss Retention after 2000 hours
≤ 2 ∆E Colour shift after 2000 hours |
| Coating Thickness | ISO 2808 | ≥ 355 µm |
| Continuity of Coating Layer | NACE SP0188 | ‘Holiday’ free ≥ 5 v/µm |
Cautionary Words
- Be careful to ensure the performance test reflects how the coating is intended to be used. Avoid wasting resources testing the weathering performance of a primer where a mid and/or top coating layer is to be applied. It is much more efficient to test the full coating system applied.
- When referencing ‘minimum’ requirements make allowances for below minimum or sub-optimal results, especially where the coating is likely to be very close to the minimum requirement. It is almost a certainty that where a coating is close to a minimum specification, say 375 µm measured coating thickness on a requirement of 355 µm, that there will be areas of the coating that might be (just) below the minimum requirement. Where this is reasonably foreseeable, it is advisable to build in a level of tolerance, no more than 10% of readings below minimum, based on 1 reading every 2 m2 and not less than 325 µm.
Specifically Named Products
A huge advantage of specifically naming a product in a coating specification is that the project engineer has already determined that the coating products listed will satisfy the intended application and requirements of the owner. This type of specification will often list comparable products and coating systems from a range of competitive suppliers, each system ‘equal’ to the next. The coating application contractor can then select an appropriate system according to ease of purchase and application.
Applicators that have worked on specifically named coating specifications will be familiar with the requirements listed by SaudiAramco paint standards, KOC (Kuwait Oil Company) paint standards, NORSOK M-501 paint standards or others.
Although the coating systems are ‘equal’ there may be differences in price, speed of delivery, drying times, cure temperatures, the need to use specialist coating application equipment and so on. An expert coating applicator will have the knowledge to choose a coating system that they feel can best meet the performance requirements of the project engineer or owner.
About Northpoint
Northpoint is strategically located in the North West close to Manchester and services a customer network across the UK and internationally. Northpoint is a UK leader in powder coating solutions and is experienced in delivering professional coatings that meet DWI (Drinking Water Inspectorate) coating requirements, NORSOK M-501 coating requirement for use in both on and off-shore applications, SaudiAramco, KOC, Petrofac and more paint specifications typically specified for petro-chemical processing applications.
Northpoint is a specialist provider of FBE (Fusion Bonded Epoxy) coatings and systems that use FBE as a part of the corrosion protection coating system employed. Our collaborative approach to creating bespoke coating solutions for our customers has allowed us to build a strong reputation in the powder coating industry.
About the Author
Philip Dawson has over 30 years’ experience in corrosion protection coatings application, management systems and is an established coach/mentor. Philip’s role at Northpoint has changed over the years from one of shareholder to an internal consultant role, as well as providing the technical support where functional coatings are being specified.
Philip’s experience and qualifications extend to include Lead Auditor of ISO 9001 QMS, ISO 14001 EMS, ISO 45001 OHSMS & ISO 27001 ISMS as well as holding an Executive MBA and PGD’s in Occupational Health & Safety, Management and Executive Coaching & Mentoring.
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