Materials Selection and Design Challenges Traditional Anticorrosive Coatings

Owners of assets in harsh environments know that corrosion is a perennial adversary and demand the highest quality in protection. Traditionally, inorganic zinc-rich coatings (IOZ) have been the preferred primers for these environments, thanks to their enhanced anticorrosive properties.

However, inorganic primers such as zinc silicates present some disadvantages in their application properties in comparison to the use of organic counterparts. The main reservations include their sensitivity to surface preparation, microcracking due to over application and long curing times influenced by the need for humidity to cure. This means that highly skilled applicators are vital to the successful application of an inorganic zinc silicate coating and that productivity is compromised by their long curing times. Mindful of these challenges, at worldwide paint and coatings specialists Hempel (Lyngby, Denmark), we have invested heavily in research and development (R&D) to develop coatings that reduce the application risk.

The True Challenger

In late 2017 we launched a versatile activated zinc primer—Hempadur Avantguard® 860—that combined best-in-class corrosion protection, at the level of an inorganic zinc silicate, with the application benefits of an epoxy. This truly unique solution challenges traditional anticorrosive coatings.

Hempadur Avantguard 860 not only delivers superior protection, but it also boosts productivity, bringing further efficiencies to asset owners. With a recoating interval of just one hour, it offers at least four times faster drying than coating systems based on zinc silicates. Highly flexible and versatile, Hempadur Avantguard 860 can be applied year-round and at temperatures as low as 14 ˚F (-10 °C), and with no restrictions on minimum relative humidity.

The Technology Behind It

Hempadur Avantguard 860 incorporates Hempel’s ground-breaking, patented Avantguard technology. The secret to this science is that by combining the ingredients used in traditional zinc epoxies with two new elements—hollow glass spheres and a proprietary activator—the zinc becomes much more effective. By enhancing the performance of zinc in this way with the galvanic effect, Avantguard 860 can outperform conventional zinc epoxies and provide corrosion protection approaching that traditionally associated with zinc silicate-based systems.

What sets this coating apart is that the unique formulation also improves the coating’s mechanical strength, which is essential for applications where the steel is exposed to extreme mechanical stress. In a standard zinc epoxy protective system, the zinc primer is the weakest mechanical point and, as a result, cracks can form in the coating as the steel expands and contracts under extreme conditions. Avantguard coatings are different. The glass spheres absorb most of the impact from the initial crack to stop it from developing. Then, the sub-products formed during the zinc activation process occupy the space left by the micro-crack, preventing it from developing, and extending the lifetime of the coating and consequently the protection of steel.

Hempadur Avantguard 860 conforms to the compositional requirements of SSPC Paint 20 2002, Level 1, Type II. Coating systems based on Avantguard 860 meet the toughest anticorrosive test requirements for the most severe environments, including ISO 12944 CX, and are prequalified for NORSOK M-501 Ed.6, System 1.

Hempadur Avantguard 860 at a glance:

• Certified to the highest anticorrosive test requirements including NORSOK M-501 Ed.6 System 1, ISO12944 CX and Level 1 Type II in SSPC Paint 20 Std. (Ed. 2002)

• Based on Hempel’s advanced and proven Avantguard technology

• Fast drying: at least four times faster than zinc silicates—a three-coat system can be applied in a single shift

• High mud cracking resistance of two times better than inorganic zinc silicate coatings

• Flexible application—wide application temperature range, can be applied in temperatures down to 14 ˚F (-10 °C)

• No need for a mist coat as required for inorganic zinc silicates.

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