Special Report: Delaying offshore maintenance
Lasse Isaksen, global concept director for offshore, Jotun, says engineered solutions provide offshore corrosion control
When it comes to corrosion protection of offshore installations it is worth keeping in mind that the environment is working decidedly against them. In essence, you have steel behemoths placed in the most corrosive environments imaginable, and all that keeps them from corroding to the point of failure is a paper-thin layer of coating.
This coating will eventually fail and give rise to the need for maintenance, and the problem is that offshore maintenance is complex and costly. It is estimated that applying coatings offshore is approximately 10-15 times costlier, on average, than it would have been in a yard. It naturally follows therefore that the name of the game is to extend the period between each time maintenance becomes necessary.
Challenges to protection offshore
On a live offshore installation one does not have the luxury of easy access to the areas to be maintained, nor is it guaranteed that the best tools for the job can be employed.
At new construction stage, one can easily make use of abrasive blast cleaning to achieve an ideal surface, and one can apply paint by airless spray under highly controlled conditions. During maintenance everything is generally turned upside down: mechanical surface preparation, or ultra high-pressure water jetting, becomes the norm and paint application is predominately done by brush and roller.
Without ideal surface preparation and without the ideal application method, it is a big ask to get ideal corrosion protection. This is exacerbated further if the paint system chosen is not designed to overcome these challenges.
Existing paint solutions
To overcome the challenges posed by power tool prepared surfaces, paint manufacturers will typically recommend surface tolerant primers to be used.
Many such products exist on the market, but they tend to be limited to a select few technology types, epoxy being the most prevalent. Zinc rich primers are widely accepted as offering superior protection and lifetime for atmospheric areas, but very few are suitable on power-tooled surfaces on larger areas, and fewer still also offer sufficient build and finish when applied by brush or roller.
Furthermore, whereas brush and roller is the dominant application method for maintenance most coatings utilised are actually designed for application by airless spray since they often have to comply with international test methods. This is significant because products optimised for airless spray generally offer lower and/or uneven film build when applied with brush and roller.
Unless correct film thickness is achieved one will lose out on the barrier effect it is supposed to offer, and an uneven film will have weak points for corrosion to take hold. In practice one can compensate for lower film build by applying multiple coats, but this in turn is wasteful as it slows down the process significantly.
When Jotun set out a few years ago to develop a new range of products for offshore maintenance it was with a simple idea in mind: that they should be made with the actual usage situation in mind. There were two key considerations – one, they should give good adhesion to the kind of surface preparation methods that are prevalent in this environment; and secondly they should be designed primarily with brush and roller application in mind. This meant that correct and even film thickness should be achieved in only one coat, and that they should be easy to mix and apply.
As a performance criterion Jotun believed that any new system should perform just as well in a maintenance situation, as comparable systems would when applied in a yard. To measure success, it was decided to test efficacy according to demanding new construction standards. However, whereas these standards call for application by airless spray on well-prepared substrate, Jotun would instead go further and test on samples applied by brush or roller on far less ideal substrates.
Jotun’s offshore system
As a world first, Jotun has successfully launched a system compliant to NORSOK and ISO 20340 (now ISO 12944-9) by testing on a wide range of surface preparation methods, and applied by either brush or roller. In fact, Jotun has ten third party certificates tested on various substrates and application methods.
By being specially designed for brush and roller application on power tooled and water jetted surfaces, one can achieve maintenance intervals up to 50% longer when compared to traditional solutions in the market.
Through having products that can achieve required film thickness in one coat, rather than multiple coats, timesavings on paint maintenance can at the same time be reduced by 40%.
This solution has, in short time, gained approval for more than 20 different specifications with major asset owners and it all comes back to one very simple idea: that products should be fit for the realities of the maintenance situation.