Winning the fight against corrosion

Corrocoat are renowned for their expertise in the manufacture of specialist performance coating systems, which provide long-term protection in aggressive immersed and non-immersed service: providing coating solutions for process vessels and storage tanks in diverse applications such as oil storage, aviation fuel, sewage treatment, activated carbon filtration, chemical and hydrocarbon storage, and many more. Corrocoat also advises on, and implements, unique and robust methods for the repair of roofs, walls and floors on storage tanks. Advanced composite materials can be used as an alternative to welding and replating, ensuring repairs can often be carried out without hot work.

Polyglass is a high-performance range of protective coatings developed by Corrocoat. Often applied by airless spray, and with no primer required, these products offer excellent application properties and are highly-effective in extremely corrosive environments. They are ideally suited for the protection of tanks and vessels.

Specially formulated to give optimum application properties and short cure cycles, Polyglass materials offers a remarkably low permeation rate, combined with excellent resistance to abrasion and cathodic disbondment. The inherent durability and undercutting resistance of this high performance coating enables it to remain intact, even when damaged through to the metal substrate, with negligible under-film creep.

Whilst proprietary holding primers with extended over-coating times are available for ease of surface preparation if required, Polyglass products require no primer, are easy to apply, cure quickly and can be applied in single or multi-coat applications. They provide an extremely tough, long life, highly corrosion and chemical resistant lining for tanks and vessels. Quick cure times mean that Polyglass can be walked on and over-coated within a few hours of application, which is ideal for tank floors.

The coatings in this range are specially manufactured using ECR (extra corrosion resistant) glass. ECR glass flake imparts better qualities to Polyglass than standard glass flakes, and in conjunction with highly modified resin systems, provides a very low permeation, mechanically strong, tough and abrasion resistant coating with outstanding long-term performance.

Polyglass VEF is a cold cured glass flake vinyl ester acrylic co-polymer, thixotroped with polyethylene fibre and is ideally suited to aggressive immersed environments, where superior resistance to chemical attack is required. It can also be used in aggressive atmospheric or spillage conditions. Corrocoat also supply high performance glassflake epoxy materials for immersed service applications.

The two case studies below showcase just how durable these materials are in the protection of tanks.

Repair and corrosion protection for surge tanks

Corrocoat was asked to protect and refurbish an oil storage tank at a UK oil terminal. The oil was delivered semi-processed to the terminal and fed directly into processing. The surge tanks allowed the oil to be diverted and stored in the event of production problems.

The oil container (both seawater and H₂S), and the large storage tank had suffered from sulfur reducing bacteria (SRB) attack. Corrocoat was contracted to line the floor and 1 m of the wall. Glassfibre laminate was used on the wall floor interface and damaged areas, in addition to specially formulated vinylester filler materials.

The sulfate reducing bacteria was neutralised using a biocide during surface preparation, use of the vinylester technology helped to prevent the reoccurrence of this problem within the tank.

Following successful trials to demonstrate the flexibility of the coating to the oil company, Polyglass VE was selected as the most suitable for this application and was applied in two coats to achieve a D.F.T of 1.25 mm.

The fist tank was lined in March 1990 and following the success of this project, a second tank was lined in July 1993. At the time of writing this article, in April 2022, both tanks remain in service.

Coating approved for aviation fuel tanks

Based on the proven track record of lining tanks and vessels, Corrocoat Caspian was asked to tender for lining aviation fuel tanks. Due to a change in the composition of the aviation fuel within Kazakhstan, the existing tanks linings were no longer satisfactory and Corrocoat Caspian won the tender to reline four large storage tanks.

Corrocoat Zip-E has full aviation fuel approval as per EI 1541 standards, which provides performance requirements for protective coating systems used in aviation fuel handling systems. Corrocoat Zip-E is an epoxy spray applied glassflake lining which has been used in many diverse applications, including the lining of over 300 railcars in South Africa, used for the transport of aviation fuel.

Summer in Kazakhstan can be very short; cold weather in September can be expected. With this time constraint, the work had to be carried out when ambient temperatures would be suitable for application curing. In total, a surface area of 14 130 m² was coated to a dry film thickness of 500 – 700 µm.

As a further test of integrity of the coating, 21 days after the tanks had been re-filled with fuel, samples had to be sent to an Aviation Institute to attest that the coating had not tainted the fuel and affected its quality. The results were excellent and Zip E was shown to have no effect on the stored aviation fuel. The project was completed in good time before the onset of cold weather, another satisfied Corrocoat customer.

Protection against corrosion is a vital issue in extending the working life of any tank or vessel and reducing total life cycle costs. Polyglass materials alongside other protective coatings specially formulated by Corrocoat, have a proven capability of extending the service life of tanks and vessels, with expected service lives of over 20 years in many aggressive service applications.

www.corrocoat.com

Read the article online at: https://www.tanksterminals.com/special-reports/09052022/winning-the-fight-against-corrosion/