A novel coating technology has been developed in Australia to protect galvanized products from “white rust,” the form of zinc oxide that tarnishes freshly galvanized coatings, making them look dull.
Australian galvanizers now use a chromium-based treatment immediately after galvanizing to maintain a shiny appearance during the early life of the product.
Chromate is widely used as a conversion coating on metals such as zinc, aluminum and magnesium to help protect against short-term corrosion and as a base for additional protective coatings.
But although chromate is an excellent corrosion inhibitor, it is highly toxic.
The Australian government’s Commonwealth Scientific and Industrial Research Organization says in a statement chromate still is widely used in Australia, but the industry is keen to find an alternative.
To that end, CSIRO scientist Scott Furman has created “Quench Coat.”
“Quench Coat is a simple drop-in replacement for chromate in the galvanizing industry,” Furman says in a statement.
“Some alternatives to chromate require the use of hazardous solvents, which have occupational health and safety issues,” he says. “Because Quench Coat is water-based, it has none of these disadvantages.”
In CSIRO’s trials, Quench Coat matched the performance of chromate in accelerated and outdoor exposure tests. It is more readily paintable than chromate, with good adhesion characteristics, and well-suited to applications where the metal product needs other protective coatings, the organization says.
Furman says because this technology eliminates the need to use a toxic chemical during manufacturing, products can be marketed with a “green” label, which may help distinguish them from those still using chromate coatings.
Queen Coat’s developers say the cost and performance of the material are similar to chromate, without the additional costs associated with the disposal of hazardous chromium wastes. Quench Coat will contribute to a safer working environment and reduce health risks to workers, Furman adds.
Quench Coat specifically was designed as a chromate replacement for hot-dip galvanizing, but the coating also works with other types of galvanizing and forms on other metals, including aluminum and magnesium.
CSIRO says it, therefore, has numerous applications beyond hot-dip galvanizing and is capable of providing green solutions to a wide range of industries.
The government research agency has identified a number of potential end-users eager to move away from the use of chromate-based manufacturing methods and is seeking a coatings company to produce and distribute the technology commercially.