Hexavalent chromium compounds are a key ingredient in coatings used to rust-proof steel. They also happen to be carcinogenic. Researchers, therefore, have been looking for non-toxic alternatives that could be used to keep steel items from corroding. Recently, scientists from the University at Buffalo announced that they have developed such a substance. It’s a varnish that incorporates graphene, the one-atom-thick carbon sheeting material that is the thinnest and strongest substance known to exist.

The composite coating was created by a team led by chemists Sarbajit Banerjee and Robert Dennis.

Initially, pieces of steel coated with it lasted for only a few days when placed continuously in brine. Once the dispersion and concentration of graphene within the varnish were tweaked, however, treated steel was able to last for about a month under the same conditions – the brine used in the trials was far saltier than regular seawater, so the steel would reportedly last for much longer in real-world scenarios.

Three versions of the varnish, containing varying amounts of graphene

Although the exact makeup of the coating isn’t being released, Banerjee believes that “the material’s hydrophobic and conductive properties may help prevent corrosion, repelling water and stunting electro-chemical reactions that transform iron into iron oxide, or rust.” Additionally, it is said to be compatible with the existing hardware at facilities that currently perform chrome electroplating.

The university has applied for a patent for the varnish. Tata Steel, which sponsored the research, already reserves some rights to the technology. The scientists are now working on improving its staying power, and the quality of its finish.

This isn’t the first time that the anti-corrosive qualities of graphene have been explored. Earlier this year, scientists from Nashville's Vanderbilt University reported that they had used a process of chemical vapor deposition to grow graphene directly on copper and nickel surfaces. When subjected to corrosive elements, the metals respectively corroded seven and 20 times slower than untreated samples.

Source: University at Buffalo