Feature 1 | PAINTS, SEALANTS & COATINGS


Glass flake epoxies - a proven success, but why?


Glass flake epoxies are well established coatings in the offshore industry. International Paint’s Dr Toby Stein and Andrew Clark discuss the merits of different systems and industry experience to date


G


lass flake epoxy technology has been used in the offshore industry for over 30 years to protect the


splash zones of assets and heavy duty areas including heli-decks. Its popularity grew rapidly during the North Sea oil boom in the 1980s, as UK yards began to realise that these new products were easier to apply (by switching from low solids coatings to high solids glass flake epoxies, requiring fewer coats, they could increase their productivity). Oil majors too began to see the


performance benefits of choosing epoxies reinforced with glass flake. Today many projects still rely on these proven products for corrosion protection. Te outstanding reliability of glass flake epoxy coatings continues to be well documented.1


Glass


flake epoxy coatings have been extensively tested to offshore standards including Norsok M-501 (edn. 6) System 4, 7A and 7B, and perform very well against them. As with all technologies, the coatings


must be robust to allow for easy application. Coating failures are oſten attributable to poor application. Surface preparation may be carried out either incorrectly or not as specified. This is one of the key factors explaining the dominance of epoxy products in the heavy duty coatings business. In general, they are easier to apply than alternative thick film, three pack technologies. In the offshore industry, where longevity is critical, standards of surface preparation are higher than in the commercial maritime sector. Owners, whose assets are designed to withstand extended lifetimes, insist on these superior standards, with surface preparation grade. People are keen to discover whether


single pack technologies are an alternative to glass flake epoxy coatings. However, at this moment in time, no such viable technology has come forward that can offer the same build thickness and performance that epoxy technology delivers in the heavy duty


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International Paint’s Interzone 1000 glass flake epoxy served Hutton well for almost 30 years


offshore market. Epoxies also have good compatibility with tie coats, necessary for the application of foul release systems. Foul release systems facilitate the rapid removal of unwanted marine organisms, allowing faster inspection of submerged areas.


Lamellar glass flake One type of glass flake epoxy coating still widely used all over the world is a high solids epoxy with the addition of >30% lamellar glass flake present within the dry film. Tis type of formulation provides outstanding corrosion protection and also boasts benefits for application yards. Such a heavy duty anticorrosive coating can withstand the working procedures during construction, minimising the risk of damage to an asset. Te coating has high impact and abrasion


resistance, enabling the use of heavy liſting equipment during fabrication with minimal need for repair work. Te high film thickness also ensures that, in the event of any damage being sustained, it is unlikely to reach bare steel. Tis is an important point to consider when deciding to choose a glass flake epoxy coating. Such characteristics prevent the application process and coating integrity from interrupting the fabrication process.


Making the right choice Te selection of a glass flake epoxy coating can be challenging due to the wide choice currently available on the market. Broadly speaking, these can be categorised into those with low levels of glass flake within the dry film and those with high levels present. It is those with high levels of glass flake, with a high aspect ratio (or lamellar glass flake), which are used for long-term protection of offshore assets. Te aspect ratio refers to the relationship between surface area and particle thickness. A large surface area with a low thickness provides an increased aspect ratio. A coating will always require careful


formulation to ensure it meets high-end performance needs. Coating manufacturers have many options available to them in formulating epoxies with glass flake. For example they can:


• Optimise use of glass flake to increase a coating’s performance


“glass flake epoxy”.


Tere is a big difference between these two options. Screening of commercial glass flake epoxies can reveal a 30% variance in the levels of glass flake present within the dry film. As such there can be big performance differences between glass flake epoxies. Coating manufacturers may choose


between different types of glass flake. For instance, lamellar glass flake will add a long “tortuous” path for ions to migrate through the dry film, providing excellent barrier protection. It is important to realise that a high aspect ratio lamellar glass flake is expensive, which adds to the cost of ‘the paint in the can’. Many alternative glass flake epoxies use micronised (ground up) glass, but this may not significantly improve anti-corrosion performance. Micronised glass flake has a low aspect ratio and this


Offshore Marine Technology 1st Quarter 2013


• Add the minimum quantity of glass flake to ensure a coating can be classified as a


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