The importance of ambient cure for high-temperature coatings: AkzoNobel

UPC Refinery iStock 178495335Due to increasing demand for energy around the world, the prevalence of global megaprojects within the oil and gas industry is increasing

Process pipes, valves and vessels may be manufactured and coated in China or Korea before being transported to the final project location, such as the UAE. During the transport and fabrication phase, coated steelwork may spend extended periods exposed to harsh offshore/coastal environments prior to going into service. This means coatings must be able to provide protection throughout an extensive construction phase, in addition to the in-service lifetime of the steel

While standard atmospheric anti-corrosive coatings such as inorganic zinc silicates and epoxies are designed for long periods of exposure in corrosive offshore environments, temperature resistant coatings often rely on some degree of post-cure at elevated temperature to attain full anti-corrosive properties and damage resistance. This is especially the case for inorganic silicone coatings, often collectively termed Inert Multpolymeric Matrix (IMM) coatings, which have widespread use within the oil and gas industry due to their excellent flexibility and resistance to temperatures up to 650°C (1202°F).

The deficiency in ambient cure has led to examples of IMM coatings corroding prior to entering service for their intended end use. Although inorganic zinc silicate primers can be used to protect IMM coatings against ambient cure breakdown, they are difficult to apply correctly and the requirement for an extra coat in the system reduces productivity. Most importantly, they are not recommended for use under insulation due to the rapid consumption of zinc in the harsh environment on the steel surface. A coating is required that combines excellent ambient cure and high heat performance, without the use of an inorganic zinc silicate primer. But how do we demonstrate its suitability for corrosive ambient temperature environments?

ISO12944-9:2018 - A standard for the most aggressive corrosive environments

Traditionally, several internationally recognised standards have been developed to provide an indication of how a coating system will perform in-service, in an accelerated timeframe and to assess the suitability of a coating for a particular environment.

These include ASTM B117 and ISO 9227, which involve continuous exposure to salt fog at 35°C (95°F), and ASTM G85, a modified salt fog test with wet/dry cycling and low pH. One of the concerns with ASTM B117 and ISO 9227 is that continuous exposure to salt solution is unrepresentative of conditions experienced by coatings in the field. Although modified salt spray standards have been developed, this overall problem remains.

The aim of the ISO12944-9:2018 standard is to provide an accelerated test which subjects the coating to conditions more closely related to those seen in the field. This includes UV and condensation exposure at high temperatures to mimic the strong sunlight that the coating experiences in an offshore environment, exposure to hot salt fog which accelerates the corrosive conditions in a CX environment, and a freeze cycle to introduce the stresses associated with diurnal and seasonal temperature variations.

A reliable solution to ambient temperature corrosion

Interbond 1202UPC is a next generation Universal Pipe Coating developed by AkzoNobel; this two pack, aluminium pigmented, silicone coating provides corrosion and heat resistance at temperatures from -196°C to +650°C (-321°F to 1202°F) on insulated and uninsulated steel.

A vital aspect of this product is that unlike traditional IMM coatings, ambient cure anti-corrosive properties are attained prior to post cure during high heat service.

Always consider the journey of the coating prior to service

When specifying coatings for service at elevated temperatures, the ambient temperature conditions which the steelwork may be exposed to prior to going into service must be considered. ISO12944-9:2018 is an internationally approved standard which is designed to provide a reliable indication of how a coating will perform in an offshore CX environment, in an accelerated timeframe. Interbond 1202UPC complies with the requirements of the ISO12944-9:2018 standard and is well equipped to withstand the severe conditions faced between application and entering high heat service.

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