One of the most difficult things about developing a new coating for metal is getting the (organic) paint to stick to the (non-organic) metal. Up until now, coating specialists have used heavy metals, such as iron phosphate, zinc phosphate or chrome to aid this process, but using these substances adds to cost and, if spilt can have a negative effect on the environment.
But now a new coating has been developed that promises to be both hard-wearing on metal and yet is kind on the environment. It is a system which uses a primer based on water and silica, followed by a layer based on polysilicates.
As the industry journal DurabilityandDesign, writes, “First, a base layer of water mixed with silica is sprayed on to the metal, creating a chemical bond with the metal. This not only cleans the metal but also deposits silica onto the surface. This coating protects the metal while also acting as a primer for the second layer, which was designed to bond well to paint.
The second layer contains polysilicates, the basis of which is silicon, reported to be the second-most abundant element in the Earth’s crust. Silicates can be modified to stick to both metals and paints.”
The breakthrough was made at Brock University in Ontario, Canada in cooperation with the business enterprise Vanchem Performance Chemicals, and was led by organic chemist Paul Zelisko, who described the coating as being based simply on water and reactive sand, so that, “If the material happens to get flushed out or it leaks, you’re effectively releasing sand and water into the environment.”
So far, tests on the new coating have shown it to be extremely effective against corrosion, as the Brock University website explains, “When the industry wants to determine whether or not a coating product is effective, the treated metal sheets are put into salt-spray chambers, where a fine mist of salt water is continually sprayed onto the metal until it starts to show signs of corrosion. The industry standard is around one thousand hours, ‘But,’ says Zelisko, ‘our coatings ranged anywhere from 1,800 to 3,000 hours, in some cases almost three times as good as what the industry requires.’”
Vanchem vice president Ian McLeod is hopeful that there will be high demand for the product, as it is part of a trend towards environmentally friendly coatings.
“The industry has switched over to greener technologies; they want to get rid of the heavy metals,” he explains. “Large corporations and companies want to be environmental stewards. They want to be able to say, ‘look at what we’re doing, we’ve replaced the old zinc phosphate technology with a new silane-based technology that doesn’t have any environmental impacts.’”
As well as being eco-friendly, the new coating is expected to be an aid to coating and paint manufacturers who wish to avoid adding heavy metals to their feedstock supply lists. Unfortunately, despite silica being an overwhelmingly abundant resource, the new process has yet to be proven entirely cost effective.
As McLeod states, “the initial price of a ‘green’ coating may be more expensive than a zinc phosphate one. But, factoring in environmental disposal, maintenance and other costs associated with non-green coatings, companies could save money in the long run.”
So for now it seems the jury is out on the true impact this coating will have on the market, as it will depend greatly on a paint supplier‘s long-term plan and the consumers’ willingness to pay extra for the eco-label. Of course future changes in coating feedstock prices, such as a price increase in heavy metals relative to silica prices, will make all the difference to this coating’s success in the marketplace.
Failing that it would be down to changes in protective coating legislation or paint manufacturing, or a shift in customer attitudes towards saving the planet. And for that you must ask yourself, “Would you pay more to ensure your coating is ‘green’?”