Two applicators spray painting red ship hull
Two applicators spray painting red ship hull

Spotlight on surface preparation and application

How is the full performance and quality of marine coatings achieved? There is no simple recipe, but proper surface preparation and application is key.

Paint application is usually carried out either at the initial newbuilding stage or during regular dry-dockings, and the owner is reliant upon its classification society and superintendents to ensure the coatings are applied correctly by the painters/contractors. However, incorrect preparation and application does happen and are often the causes for poor coatings performance.

According to Min-Sung Kim, Corporate Technical Support Engineer at Jotun, a thorough work process during the application, including surface preparation and application is crucial to achieving good coating quality and expected performance, but the end result is dependent on several parts.

“Paint is a ‘half-finished’ (read: semi-finished) product and is ready to deliver the intended performance. The remaining ‘half’ is achieved by proper surface preparation and application, and therefore full performance and quality is achieved when there is sufficient focus on both parts,” says Min-Sung Kim.

He continues, “Also, to maintain optimal performance over time, proper maintenance and use by the ship owner is required. So all parties are essential to obtain a good coating quality. Any expectation about good coating quality must be based on the acknowledgment of this three-way responsibility. A single party cannot reconcile all the different interests, for example, the productivity, quality, use in service, maintenance program and guarantee aspects.”

Min-Sung Kim was asked to share his thoughts on the subject of surface preparation and application in a recent Q&A

1. What are the key challenges as you see them?

Achieving good coating quality is not a quick fix and there are many factors that affect coating performance and longevity. Proper surface preparation and paint application is crucial to achieving good performance, as is proper film thickness building and sufficient curing time.

Regarding surface preparation, there are international standards or market recognised surface preparation grades that are reasonably well followed. However, it is an extremely competitive market – both as regards newbuilding and dry-docking projects – and some parties focus on quality, while others are more commercially-oriented.

Coating work, then, is influenced by this business situation. One may focus on the better quality, while another one focuses on the commercial aspect. As a result, unexpected deterioration of the coating system may be seen due to inferior surface preparation and application, and a paint manufacturer (and their technical representative) is very often caught between different interests.

The paint itself is a semi-finished product, so in the end, the coating quality is very much dependent on how well it has been applied. Even with the same product and the same dry film thickness, the end quality will be quite different with variations in surface preparation and application. In practical terms, then, achieving an even grade of surface preparation, including steel dressing, roughening, and cleaning over the huge surface areas to be coated, is often challenging.

2. What are the solutions to meet these challenges?

One key aim, as a paint manufacturer, is to develop a product which performs good even if the ideal surface preparation/application is not feasible in the given situation.

Typically paint manufacturers work to an agreed specification, which is the priority. If any deviation is requested, the maintenance and next major refurbishment plan need to be reviewed, to see whether the maintenance can cover such deviated quality/lifetime. The lower grade of coating work, the shorter lifetime of the coating film, and consequently, the shorter maintenance interval to be arranged.

Occasionally the paint manufacturer may be asked to check the quality of the coating work, for instance, when it does not meet the expectations of the owner or yard. A risk assessment is then arranged, comprising technical and commercial considerations, and even future business potential.

The answer should also be technically reasonable, because the owner may have other projects in other yards using the same paint. The yard may also have other projects with other owners, but using the same product. So the paint manufacturer must recommend solutions considering all aspects of the project, not merely repeating what has been written on paper.

3. How can paint manufacturers work with owners and operators to be part of the solution?

Communication is crucial, especially for cross-border projects. A strong global network should maintain close and effective communication, following global procedures and using local competence to ensure the project’s success.

As an illustrative example, a European shipowner delineates his coating specification and sends this to the site representative, for instance, in a Korean yard. The specification might look good as is, but there may be some hidden challenges from a practical point of view since the building practice and available resources on site tend to differ from region to region.

Normally paint manufacturer representatives in both the owner’s country and the yard’s country communicate closely to provide the best solution to both the ship owner sitting in Europe and its site representative in Korea, and also to the ship yard who is the customer of the paint manufacturer in the yard country. The paint manufacturer utilises the global procedures and local competence.

In short, this means that a paint manufacturer’s corporate unit sets principles and guidelines to support regional/local business, and the regional/local units follow the principles together with their local experience and competence, bringing the solutions together to fit the real situation around the project.

4. Any practical advice regarding proper surface preparation and paint application?

There are industry standards for surface preparation and the ship owner should expect that these will be met. The skill and experience of the contractors, environmental conditions and how the coatings are allowed to cure before use are also important factors that will impact on the coating performance. Training shipyard personnel is also important so that they are updated on preparation and application issues, techniques and developments.

Min-Sung recommends owners and operators to use surface preparation and application guidelines that provide practical support.

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