Best Practice in Protective Coatings

As infrastructure ages and budgets are tightened, maximising the performance and lifetime of protective coatings has become a high priority to many industries.

No longer seen as child’s play, it is now recognised world-wide that specifying and applying protective coatings is a science that requires the skills and experience of trained competent professionals.

In this feature article, Mick Flounders, Contracts Director at CSC Services examines the key elements of a successful protective coatings programme.

Audit of environmental conditions

All coatings programmes should start with an environmental audit. It is imperative to understand the environment in which the coatings will perform. Humidity levels, temperature ranges and air pressure are some of the factors to be considered so the optimum coating system can be specified.

Correct Specifications

The overall success of a protective coating scheme can be influenced by many factors and starts with a well-prepared specification. The specification is an essential document that is intended to provide clear and precise instructions to the contractor on what is to be done and how it is to be done. It should be drafted by someone with appropriate technical expertise, and it should be clear as to what is required, and what is practical and achievable.

The specification should always consider factors identified in the environment audit and take into account the service environment of the asset or structure. The desired life expectancy should also be factored into any specification.

Proven Materials

With a huge range of specialist coatings on the market and numerous qualification standards for coatings materials used in various industries, specialist advice should always be obtained. Many contractors such as CSC Services will work alongside coatings manufacturers to ensure they are fully up to date with the latest product ranges and application training. A competent contractor should however be able to offer independent advice on the best specification to suit your requirements based on industry knowledge and previous experience.

Trained and Qualified Personnel

The experience and training of the applicator and contract manager are fundamental to the success of the project. Some products have high abrasion resistance, tensile strengths and high elongation properties. Using a high tensile strength coating with no elongation properties on a substrate where movement may occur will result in cracks and failure in the coating. A lack of specialist knowledge may result in incorrect mixing of products. Most industrial products are two pack systems. If they aren’t mixed correctly they will not cure correctly.

Using a specialist contractor will ensure the correct application method of a product at the correct application temperature. Curing time is also a key consideration. Coating products require a certain amount of time to chemically bond as specified in the technical data. Not leaving sufficient time may mean the product fails. After curing, the product should be fully cleaned and inspected for fails.

Correct Surface Preparation

All too often protective coatings will fail due to incorrect substrate surface preparation. Dirt, grease, dust and other surface latents will form a barrier between the substrate and coating to be applied which means there is no mechanical bond present. Surfaces generally need to be grit blasted or hydro blasted to form a mechanical key. Correct substrate surface preparation of concrete for instance involves correct application of pore fillers and fairing coats to address blow holes or honey combing in concrete surfaces. Fairing coats need to be applied correctly to leave the required surface profile.

Quality Control

Inspection ensures that protective coatings systems are installed as they were specified. Quality control should be provided by the contractor and ideally quality assurance performed by a third-party inspector.

Holiday (pinhole) testing for example should be used to ensure a coating is pinhole-free and installed as specified. Atmospheric coatings typically rely on mostly visual testing to verify the continuous film installation.

CSC Services use a certified coating inspector to oversee all coating work. The qualified inspector will discern the difference between degrees of abrasive blasting; take surface profile readings; take dry film thickness (DFT) gauges by applicator and take wet film thickness gauges on completion as per specification such as SSPC-VIS 1,1 VIS 2,2 and PA 2.3.

Maintenance and aftercare schedule

After the coating is installed, maintenance shouldn’t be forgotten. Very often, holidays and missed spots will manifest within the first year. Early maintenance efforts can correct these problems and stem the flow of additional coatings degradation. If early maintenance is practiced, further maintenance efforts will usually decline until the coating starts to reach the end of its designed life. At that point, effective and consistent maintenance efforts may provide many additional years of service.

All of the above elements are essential for a coating program to perform to its full potential. For advice on any protective coatings or repair services call 0191 410 3444.

Mick Flounders is a Coatings Inspector, and NACE certified.