Protective Coatings for Marine Structures

Operators face the costly and ongoing challenge of protecting offshore structures from corrosion and damage by abrasion.

Both abrasive and corrosive, the marine environment is unforgiving of maritime structures such as offshore platforms and rigs and ocean-going vessels - all of which are major investments for the companies operating them. Corrosion can affect all structures and activities in the marine environment.

The most vulnerable areas are the superstructure, decks, ballast tanks, and anchor or chain wells. These areas are subject to extreme saltwater, chemical agents, and abrasion. The marine environment is also harsh on surface coatings, both in terms of how they wear and applied.

One way to minimize and mitigate the effect of some types of corrosion is by using flexible surface coatings that are resistant to chemical attacks from petroleum products and salts. A corrosion barrier must-have durability and flexibility and be impervious to the wide range of agents that affect maritime structures.

Spray-applied anti-slip surface coatings provide walkways and decking that are safe for people moving about offshore structures or vessels.

Protecting a Platform Deck From Abrasion

Coatings specifically designed for marine structures in the oil-and-gas industry can reduce the drilling operation's abrasive impact.

A deck on an oil rig with 14-meter lengths drill pipes is susceptible to large amounts of abrasive damage. Most surface coatings are quickly abraded away, exposing the bare metal substrate to corrosion.

The deck surface must be blasted with abrasive to remove any coatings. Profile the surface to ensure optimal adhesion to the primer and protective coating.

A zinc-rich primer is first applied to the prepared metal surface, over which a second spray primer is rapidly sprayed. The best primer choices for this application contain no volatile organic component (VOC) properties and can be quickly spray applied.

A thick coat of polyurea is applied over the primed area to a nominal thickness of 3000 microns (3 mm) for maximum protection. The final coating is chosen because it has excellent resistance to weather extremes and flexibility. It also offers high impact strength. Polyurea can cure rapidly, allowing the crew to walk on the surface in a matter of minutes, which means a facility can be back online sooner.

Minimizing downtime is an important consideration when applying any surface treatment. Spray coating is faster and causes less disruption to your operations. Spray coatings can be set in just 6 seconds. Pure polyureas do not react to temperature or ambient moisture, making them ideal for offshore operations.

Decking Protrusions: Coating Protrusions

Liquids mustn't run off the decks of offshore structures where pipes or other equipment enter. These penetrations are usually covered by a butyl rubber "boot" taped to both the pipe and the deck. The rubber boot and adhesive can be damaged by salt and ultraviolet light in just a few months.

The butyl rubber and adjacent steel surfaces can be scuffed and cleaned to extend the life of deck penetration boots. Before applying the flexible membrane, it is essential to remove all oil, dirt, and coatings. Similarly, the surrounding equipment, piping, and deck surfaces must be masked off to protect against overspray.

A polyurea coating applied to deck penetrations up to 50 mm above the pipe and 100 meters onto the deck creates a waterproof, weather-resistant, flexible interface that is liquid-tight and durable.

Polyurea Coating Characteristics

Pure polyureas are formed when a liquid isocyanate is mixed under high pressure with an amine-driven resin solution. Because the double covalent bond linking the carbon atom with nitrogen and oxygen is easily broken, it is possible to create single bonds in the stable tetrahedral arrangement around the carbon. Isocyanates can be reactive.

Some polyureas come as a two-part solution that 4is mixed under high temperature and pressure (3000 psi at 65oC) in a specially designed spray apparatus. The excellent chemical cross-linking results in a flexible, dense surface. This coating is almost indestructible to water, chemicals, and abrasion.

The solid surface can be walked on in under one minute because of the speed at which pure polyurea coatings dry. Polyurea can be sprayed on any surface, even vertical surfaces up to 6000 microns thick. This is a great advantage. A thick coating of polyurea is easy to maintain.

While epoxies and paints form a solid, rigid shell, the flexibility of pure polyurea coatings allows them to move with the expansion and contraction of the underlying structure as temperatures change.

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Protective Coatings for Marine Structures

Operators face the costly and ongoing challenge of protecting offshore structures from corrosion and damage by abrasion. Both abrasive and ...

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