The underwater coating industry is a tiny niche, proof of this is that only a few paint manufacturers formulate underwater epoxy coatings due to a limited market. Compared to the overall industrial coatings industry, marine or underwater applications comprise only a small fraction of manufacturers´ sales in epoxy coatings. The reason for the slow acceptance of underwater epoxies is that underwater facility owners often prefer to replace rather than repair their underwater facilities. That view has changed, however, with the growing awareness of advances in underwater epoxy coatings and their potential to cut on costs, by eliminating the old practice of replacement with in-situ underwater repairs and maintenance.
Underwater Epoxy Coatings Applications
The two-part epoxy coatings imbued with the characteristic to perform well under water provides great value to the repairs and maintenance of piers, swimming pools, and containment tanks, wherein the surfaces to be coated are submerged in water most of the time. Underwater epoxies are easy to apply in such environments, and painting applicators trained in underwater applications can perform surface coating quite effectively.
Underwater epoxy coatings are also used in areas that are not directly submerged in water, but rather exposed to certain amounts of dampness and water saturation most of the time. Some of these structures include loading docks, marine vessels and sweating pipes, which are not inundated with water but acquire moisture due to their locations and functions.
Underwater epoxies also work well in certain locations that have high humidity levels. Ordinary paints fail in such elevated moisture environments, while underwater epoxies can handle the humidity problem effectively.
How Underwater Epoxies Work
The presence of water is the primary reason why standard coatings fail under water. When moisture seeps between the coatings and the surface, it results in blistering and cracking, and leads to eventual coating failure. Underwater epoxy coatings are designed to address this problem. Underwater epoxy coatings displace water and seal the surface completely.
Underwater epoxy coatings are impervious to water. This means that the presence or absence of water does not affect their chemical composition in any way. Underwater epoxies are derived from a special formulation of polyamines that are not moisture-attractive. Other coatings cannot work on water because the water acts as a solvent to them, causing them to thin out or react in some way when water is present. In most cases, water also reacts with one or more parts of the formulation, interfering with their curing process, which leads to coating application failure.
Generations of Underwater Epoxies
There are three generations of underwater epoxy coatings that evolved through the years from continuous research.
First generation epoxies are bubble-gum-like in texture and have a short pot life. They are kneaded the old-fashioned way and applied on the surface like bubble gum. Although they are known to contain hazardous materials, many existing underwater structures still use them until today.
Second generation coatings have better adhesion under water, replacing the bubble-gum stick-on application method. But they still store poorly and tend to powderize after some time, and retain hazardous and toxic materials. They also fail when bonded with cathode-protected substrates.
Third generation underwater coatings have better storing and pot life, and are more environment-friendly with zero-VOC formulations. The problem of cathodic surfaces has also been addressed by this generation.