Protecting steel structures in hostile environments is a perennial problem. Oriol Osso, group product manager, and Antoni Prieto, R&D manager (protective) at Hempel, describe a new coating technology that enhances the anti-corrosive capacity of zinc.
Corrosion in steel structures is a challenge that manufacturers and industrial asset owners face daily. Corrosion creates specific difficulties for those wanting to protect industrial structures and equipment.
In highly corrosive environments, such as for offshore oil and gas platforms, power plants and wind turbines, failing to guard adequately against corrosion costs dearly in shortened asset life, increased maintenance costs and potential downtime. This is where the right choice in protective coating is vital.
Innovative technology
Organic zinc-rich primers have been an established technology since the 1960s, but an important discovery was made by worldwide coatings specialist Hempel in 2007. Hempel found that only around one-third of the zinc in a standard zinc epoxy coating has an anti-corrosive effect, and set out to find a better solution. Hempel also found that only products with above 80% of zinc by weight had a galvanic protection effect.
After years of development an innovative technology – Avantguard – was introduced. It has redefined protection, durability and productivity. This zinc-rich epoxy coating exhibits the strength of traditional epoxies alongside improved anti-corrosion properties with easy application.
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 in altering the electrochemical reaction between salt, water and oxygen, allowing the zinc particles to protect the steel surface more effectively.
The enhancement in the performance of zinc in this way – the improved galvanic effect – is achieved by the effect of the proprietary activator. This increases the zinc’s ability to provide galvanic protection to the steel and means that Avantguard is able to outperform conventional zinc epoxies and provide corrosion protection approaching that traditionally associated with zinc silicate-based systems.
Galvanic protection is just one of three types of protection provided by Avantguard. The second is the barrier effect. The activated zinc in Avantguard has a high tendency to form insoluble salts throughout the film, which makes it less permeable to water penetration. This is a significant advantage when compared with traditional zinc epoxies that generally exhibit a low level of water resistance.
At the same time, the insoluble salts act as scavengers for corrosive elements from the environment. This delays the corrosion process because those elements are prevented from reaching the steel surface. This inhibitor effect is the third type of protection offered by Avantguard.
Reinforced mechanical strength
Micro-cracks in the paint can appear if an asset is continuously exposed to a hostile environment, which lead to real cracks and corrosion. The hollow glass spheres in Avantguard absorb most of the stress from the initial cracks and prevent them from worsening. The sub-products formed during the zinc activation process then occupy the micro-crack, restoring the corrosion protection and thereby helping to ensure the coating retains its anti-corrosive properties for much longer.
Pushing boundaries
A coating is often damaged during active service, causing rust creep to develop. The robust technology of Avantguard is very resilient to this creep, significantly reducing repair requirements.
Avantguard provides reliable protection for steel structures in the toughest environments. Production and construction move faster while at the same time the service life of structures is extended, and maintenance costs reduced.