We have been coating materials since we first started building structures. From rubbing wax into hides to repel water to modern steel coatings to prevent corrosion, we have been steadily improving the methods and materials used to protect and preserve construction materials. Here are two of the newest ones in development.

Detect Building Damage Using Nanotube-Embedded Coating

First developed at Rice University in 2012, nanotube-embedded coating is now ready for commercial use. This exciting new coating helps alert engineers and building owners of structural threats from wear and tear.

What are carbon nanotubes? A carbon nanotube is a small tube made out of carbon. It is incredibly small; the diameter is only nanometers wide. These unique nanotubes are made by rolling up sheets of single-layer carbon atoms, also known as graphene. Carbon nano tubes are strong and have highly conductive electrical and thermal properties.

One property of carbon nanotubes that is significant to this application, is that it is fluorescent at the near-infrared part of the spectrum. Called “strain paint”, the coating developed by Rice University will “glow” when the structure is deformed by stress.

In the past, the top two methods of monitoring structures for strain were either physical gauges or digital image correlation. With digital image correlation, the structure is painted with speckles. Images of the speckle-covered structure taken overtime are studied for changes.

The method developed at rice University allows for the combination of the nanotube strain tracking and digital image correlation by including the digital image correlation speckles in the coating.

The coating consists of three layers. First is an opaque primer with digital image correlation speckles, next is clear polyurethane to isolate the primer from the nanotubes, and finally the nanotubes suspended in toluene. 

Engineers use a small visible laser and a portable spectrometer to read the strain the nanotubes are under. Bridges, buildings, ships, and airplanes are all future applications for this new coating.

New Marine Anti-Corrosion Coating

Steel is limited, in application and longevity, by low corrosion resistance. Researchers from the Korea National Ocean and Maritime University are looking to change that through a new aluminum-magnesium-silicon (Al-Mg-Si) alloy.

Typically, you would coat steel with something like aluminum to increase steel’s corrosion resistance. This technique doesn’t work well in Marine applications because sea water contains chloride ions which can react with aluminum. This actually leads to more corrosion.

Including other elements in the coating like magnesium and silicon has been a theoretical method to get around the problem. Unfortunately, this has only been theoretical, because magnesium can’t easily adhere to the steel using the typical coating method of dipping the steel.

The researchers from the Korea National Ocean and Maritime University came up with the method to create an aluminum, magnesium, and silicon coating. The method relies on a technique called physical vapor deposition. This technique uses a metal vapor to deposit the magnesium on steel already plated with aluminum and silicon. 

Professor Myeong-Hoon Lee of the Korea National Maritime and Ocean University, who guided the study, told Civil and Structial Engieineer Media, “Our research reveals how a highly corrosion-resistant steel can be produced using a simple change in the surface treatment protocol. This makes it very meaningful for conserving energy and environmental resources.”