Alone at Sea: 4 Things to Consider in Coating Applications for Offshore Platforms
Whenever we're traveling to the beach, we always take care to pack additional things and precautions. Even if what we're going to do is to mostly lounge in the sand and under the sun, we still go through this entire routine. Things like sunscreen, a pair of sunglasses and beach towel are a necessity and sometimes, a beach umbrella and a pair of towel might also be necessary to protect yourself from the environment and if you're also going out into the ocean, a life jacket of your own would also be necessary.
The ocean and by extension, the coastal environment carries specific challenges, whether it's for our trip to the beach or for offshore structures and marine vessels, which require a set of additional protection from the environment in the form of coating. Different from the typical anti-corrosion coating, marine coatings are required to have a stronger level of protection because of the challenges posed by the environment it's being used. On the other hand, they also have to be safe enough to not damage the ocean and these considerations is why marine coating applications can be particularly challenging.
Extensive protection and friendly to the environment
The earth's ocean has increasingly become a focus for environmental protections efforts just as how it should be as water is after all the source of all life. And part of that focus is by lessening the chemical spill dumped into our ocean with coating as one of the source of that spill. This increasingly stringent regulation has resulted in the increase in the cost of marine coating applications. As a result, marine coating considerations are even more important now as the list of parameters you have to achieve gets bigger and bigger with each passing day.
Compared to freshwater environment, the ocean is notable for having a high concentration of salt. The salt contained in both the ocean and the ambient air can be particularly damaging compared to freshwater. For offshore platforms, this is especially important as those platforms will have to remain in the middle of the ocean for posterity. The main goal for the coating is to provide enough protection for offshore platforms while being friendly to the ocean and still makes enough economical sense so as not to provide unnecessary financial burden. That is no easy task but it can definitely be achieved by taking into account the 4 following considerations.
Base coating selection
The base layer of coating is the layer that protects the structure against corrosive deterioration and fluid turbulence. It is your main layer of protection, the main driver for costs and should always be the first consideration in marine coating applications. The temperature of the water they're being used on and the accessibility of the platform to the nearest land (which would affect maintenance costs) are factors that would heavily impact your choice of coating.
Certain types of coating, such as chlorinated rubber coating, comes with excellent adhesion that allows them to stick to the substrate easily while others would need the use of a primer coat or adhesives, which also would increase costs. The type of coating used will also impact the thickness level of the coating and the amount of applied coating would also affect application costs. The varying thickness would also require the use of gauges such as Elcometer to ensure you're meeting the recommended thickness level no matter what type of coating you're using.
Environmental considerations on antifouling paints
Fouling is defined as the accumulation of unwanted material on the surface of an object that negatively affect the function or performance of said object. In marine applications, this is manifested in the phenomenon of biofouling, which is the accumulation of living organisms such as algae, plants and other animals on marine structures. Typically, antifouling coatings are used to prevent this, which works by releasing particles of chemical biocide that would impede the growth of such organisms.
The use of such coating is now heavily regulated as excessive accumulation of the biocide use in this type of coating can be particularly harmful to the ecosystems. As of now, new formulations in antifouling coating have emerged in the market, which are capable of fulfilling the same objective but at a much smaller concentration of biocide. The better alternative however is the use of non-toxic anti-sticking coatings, which uses environmentally friendly organic polymers to prevent these organisms from sticking to the substrate instead of impeding their growth.
The environmental effect of VOC
VOC emissions are already heavily regulated in typical coating applications but they're even more problematic in marine applications as some coating requires the use of primer coat, which typically contains solvents. The use of solvent-free adhesives is one solution to this problem and as an alternative, the use of solid coatings as a primer coat can also be considered as solid coatings don't use solvent. It should also be noted that the base coat used should contain the least amount of solvent as possible, which would typically increase the curing time but would be much friendlier to the environment.
As with any other coating applications, surface preparation is important in the application of marine coatings. However, offshore platforms can be especially tricky because unlike with marine vessels that could simply be taken to land for re-coating, it is impossible to do the same to offshore platforms. For underwater surface preparation, it is necessary to use specialized techniques such as underwater hydro-blasting to clean the structure of any scale and grime to ensure strong adhesion of the new layer of coating.