New Green Coating Protects Metals
Academics and commercial manufacturers teamed up to develop a new coating system that is said to be tough on corrosion and kind to the environment.
Paul Zelisko, an organic chemistry instructor at Brock University in St. Catharines, Ontario, and Burlington, Ontario-based Vanchem Performance Chemicals worked together on a technology called Greencoat, which uses silicon rather than heavy metals to bind coatings to metal surfaces and paint.
What makes the Greencoat system “green,” is that it is a water-based system that, “for all intents and purposes, has reactive sand in it,” Zelisko says.
“If the material happens to get flushed out or it leaks, you’re effectively releasing sand and water into the environment,” he adds.
The team received a patent for its Greencoat silane-based pretreatment on Aug. 2 in the United States, with Canadian and European patents pending, the university announced.
A Greener Solution
When it comes to protecting steel and other metals from rust and salt damage, traditional coating systems use heavy metals such as zinc phosphate, iron phosphate or chrome to enable the inorganic substance (metal) and organic substance (paint) to stick to one another, the university reports.
However, phosphates released into the environment can cause algal blooms in lakes and rivers, damaging aquatic plant and animal life, it says, adding that solvents used in the process have the potential to pollute the environment as well.
Zelisko and Vanchem’s system varies from conventional methods by way of its a two-step process.
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, the team says. 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, Vanchem notes. Silicates can be modified to stick to both metals and paints.
The Brock-Vanchem innovation is a sign of the times, says Vanchem vice president Ian McLeod.
“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.’”
Measuring Performance, Expense
When the industry wants to determine whether or not a coating product is effective, the school explains, the treated metal sheets are put into salt-spray chambers.
When it comes into contact with metal, salty water acts as a type of catalyst, enabling oxygen to mix with metal, resulting in corrosion.
In the salt-spray chamber, 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, 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,” he states.
When it comes to overall cost, McLeod notes that the initial expense of a “green” coating may be more than that of a zinc phosphate. But, when environmental disposal, maintenance and other costs associated with non-green coatings are taken into consideration, companies could save money in the long run, he says.