Fighting Corrosion with
Silica-based Coatings
Heavy metal-free corrosion protection for coil, industrial, automotive and marine systems
Corrosion is a multitrillion-dollar problem for property owners and governments worldwide, with the National Association of Corrosion Engineers estimating the global cost of corrosion at $2.5 trillion annually. If left unchecked, corrosion also poses a serious safety concern, as rust and erosion can compromise the strength of structural supports. Everything from bridges to benches needs to be protected.
Coatings are one of the chief tools for fighting corrosion. They create a barrier between the surface and the environment, reducing oxidation. Painting the steel on buildings and equipment is done not only for aesthetic purposes, but also to protect the exposed metal from rusting.
Unfortunately, stopping corrosion is not that simple. “You think of paint as being a waterproof skin—it’s not,” says Charles Myer, senior chemist at Grace. “It definitely slows water transfer down, but it’s not zero.” Over time, moisture will build up on the surface of steel or another metal, causing it to rust. Corrosion cannot be reversed once it starts, so the material must be replaced; otherwise, it will continue to break down and will eventually fail. The key is to protect the surface and keep the corrosion damage from ever starting.
Anti-corrosion Coatings Without Heavy Metals
Hexavalent chromium (or chromium VI), which reacts with the air to create an oxide layer that protects the steel surface, is a common anti-corrosion additive. But chromium VI is categorized as a carcinogenic and environmentally toxic heavy metal, and is already banned or restricted in many parts of the world, leaving coatings chemists struggling to find substitutes.
Safer alternatives, including Grace’s SHIELDEX® silica gel, were developed to fight corrosion without the concern that toxic heavy metals pose. These highly effective anti-corrosive pigments are not classified as toxic and contain only technically unavoidable traces of heavy metals originating from impurities in raw materials. When exposed to water and hydroxide ions, SHIELDEX® will slowly dissolve, releasing calcium ions and silicate. These can then react with iron ions found at the surface of the metal to form iron silicate and calcium silicate, which form oxides to create a coating that protects the surface of the metal. SHIELDEX® anti-corrosive pigments create a thin layer of silicates that shield the metal from corrosion and close pores in the coating, extending the lifespan of steel structures and equipment.
Highly Effective Metal Protection Without Compromise
One of the challenges of working in anti-corrosion coatings is the need for customization – the optimal coating depends on a variety of factors. Considerations when selecting a coating include:
The application
The environment it will be exposed to
The type of steel
The expected lifespan
The thickness of the coating
Several varieties of SHIELDEX® are available to help improve corrosion performance, and they can work synergistically with other anticorrosion pigments, allowing you to optimize protection for your specific use.
Additional benefits of SHIELDEX® include:
Compatible with conventional methods for coating metals, so coating applicators will not need to adjust their metal pretreatment practices
Corrosion protection with minimal effect on coating viscosity, smoothness and flex
Not classified as toxic
Finely controlled particle distribution for smoothness
Lower density, meaning you can use less quantity by weight compared to conventional anti-corrosive pigments to achieve the same protection
If you’re looking to eliminate chromium VI and achieve exceptional corrosion protection, explore the SHIELDEX® silica line of anti-corrosive pigments from Grace.