Reduce marine environment’s costly effects with Polyurea



Polyurea can be used to reduce the negative effects of marine environments.

The marine environment is both abrasive as well as corrosive. It can be very damaging to structures in the maritime industry, such as offshore platforms and drilling rigs, and ocean-going vessels. These are all major investments for companies that operate them. Corrosion can cause damage to marine structures, costing the industry billions each year in prevention, control, and remediation.

Surface coatings can be affected by the harsh environment of offshore structures. The most vulnerable areas are the superstructure, decks, ballast tanks, anchor and chain wells, as well as the superstructure and superstructure. They are vulnerable to salt and chemical agents and can be damaged by people or equipment moving around. The areas where 14-m longs of drill pipe are laid out on an oil production rig are susceptible to damage. These are then dragged across the deck and pulled up for drilling operations. Most of the surface coatings are quickly removed, leaving exposed metal that is susceptible to corrosion.

Flexible surface coatings are resistant to chemical attacks from petroleum products and salts and can be used to reduce or minimize the effects of certain types of corrosion. ArmorThane's special projects engineer Hank Strathman says that a corrosion barrier must be durable and flexible, as well as being resistant to chemical attack from petroleum products and salts.

Preparation of surfaces with polyurea coatings

The platform deck must be blasted with an abrasive blaster to remove existing coatings. This will create a profile that allows for optimal adhesion of the primer or protective coating. The zinc-rich primers can be applied to the metal surface and then a rapid spray of elastomeric polyurethane primer/sealant/primer can be applied. These coatings are easy to apply and have no volatile organic components (VOC). Spray-apply a pure polyurea to the primed area, with a minimum thickness of 3mm on the deck. This will provide maximum protection. This last coating is extremely resistant to extreme weather, has high flexibility, and is strong against impact.

Strathman states that pure polyurea is an extremely modern material, which has seen rapid development over the past 15-years. When a liquid isocyanate and an amine-driven resin solution are mixed under high pressure, pure polyureas form. Reactive isocyanates result from the breaking of the double covalent bond linking the carbon atom to the nitrogen and oxygen atoms. This allows for single bonds to be formed in the stable tetrahedral arrangement around the carbon.

Flexible polyurea coatings

The requirement to minimize downtime is a major consideration when applying any surface treatment to a structure. Spray-coating is faster and less disruptive to client operations. Facilities can also be back online in no time with a spray-applied protective coating. Baker says that the beauty of pure polyurea coatings, Baker says, is their rapid setting. They can be applied quickly to create a solid surface within a matter of seconds and can be walked on with no damage in under a minute. They can be sprayed on in six seconds and cure quickly. These are both important considerations when applying an offshore coating. The coatings can be applied up to 6mm thick on vertical or sloping surfaces without sagging. It is easy to clean and recoat the surface if needed.

Polyurea's environmental impact

It is crucial that liquids don't run off the decks of offshore structures where pipes or other equipment enter. These penetrations are usually covered by a butyl rubber boot that is taped to both the pipe and the deck. The rubber of the boot can be damaged by salt and UV exposure within a few months.

A protective coating can be applied to extend the life of deck penetration boots. The boots can be coated with pure polyurea. This type of coating can be applied to boots at a thickness of 2mm or more and extended 50mm on the pipe and 100mm onto the deck. It creates a flexible, liquid-tight, weather-resistant and flexible interface for all deck penetrations up to 100mm in diameter.

The butyl rubber and adjacent steel surfaces should be scuffed and cleaned. A primer can then be applied. Before applying a flexible membrane, it is essential to remove all oil, dirt, and coatings. To protect against excessive spray, it is important to mask any equipment, piping, or deck surfaces.

Conclusion

Spray application of pure polyureas is typically a two-part mixture that is mixed under high temperature and pressure (20.7 MPa at 65°C) in a specially constructed spray apparatus. The excellent chemical cross-linking results in a flexible, dense surface. Because of its high density, the coating is almost indestructible to water, chemicals, and abrasion.

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