Making the invisible, visible - addressing corrosion with smart coatings
BP-supported scientists are researching the potential of smart protective coatings that would flag up damage, and even fix it, before it’s visible to the naked eye
Two trillion dollars a year – that is the estimated cost of corrosion globally for all industries. Rust may be unsightly to the eye, whether it is on a ship’s deck or a wind turbine, but it is a much bigger issue than aesthetics. Trying to avoid this common issue can be expensive and time-consuming.
Atmospheric corrosion can occur in any structure made of steel, and starts to happen when oxygen reacts with the iron producing the tell-tale brownish-red rust. The usual mitigation is through the extensive and continual application of protective coatings which provide a barrier to oxygen and water.
Unfortunately, coatings are prone to damage / deterioration, particularly in environments such as offshore or in the desert, and to incidental damage incurred, for example, during pipeline transportation. Damage can be slight, hard to detect with the naked eye and harder still to repair but if the coating is damaged, the barrier is breached and such locations become visible because of active corrosion. Cracks in the coating compromise the coating’s integrity and shorten its lifespan, raising the likelihood of corrosion, leaks and/or structural failure.
Scientists supported by BP may have the answer. Ground-breaking research is underway at the University of Illinois at Urbana-Champaign (UIUC), a partner in the BP International Centre for Advanced Materials (BP-ICAM), into the potential of smart autonomous coatings that would enable engineers in the energy industry to see cracks in the coatings applied to structures, equipment, pipelines and tank walls and signal before overall coating failure occurs. This would drastically improve the ability to identify and manage risk, and significantly reduce maintenance costs.
Healing powers
The secret of these smart coatings is in the damage itself. Nancy Sottos, principal investigator at UIUC, explains what the team has been doing.
“Our team embedded microcapsules, containing an indicating agent in their core, in the polymer coating,” Sottos says. “We then scratched the coating to damage it, causing the capsules to rupture, release their core contents and trigger the damage-indicating reaction in the form of a bright red colour change or, for use in dark environments such as inside tanks, fluorescence visible under ultraviolet light.”
Graphic (above): Microcapsules containing visual indicators are embedded in the coating. Upon mechanical damage, the capsules rupture and the released core materials react with the coating to locally change colour
The next stage of the team’s coatings research involves looking at the self-healing properties in certain materials; not only would the coating indicate its own damage, but its reaction would enable it to self-repair. In fact, the most sophisticated smart coatings would see the environmental factors that contribute to corrosion in situ, such as sun, wind and salt, actually harnessed to indicate and heal the damage that leads to corrosion in the first place. Not only would use of such coatings reduce the possibility of significant corrosion issues, it would also reduce the need for human intervention.
“Inspections will still always be critical, but this self-indicating technology means they will be easier,” Sottos explains.
“Coatings will last longer and need to be reapplied less often, making them safer and more cost effective by highlighting the damage by colour change or fluorescence and letting the inspector know the coating was damaged and healed in a particular spot.”
This autonomous early warning system, coupled with a self-repair mechanism, would give teams a clearer means to assess damage, reduce risk and downtime, and increase the reliability and safety of BP operations.
The BP-ICAM is a collaboration between BP, Imperial College, the University of Cambridge, University of Manchester and Illinois. The work on smart corrosion protection has already won an accolade. The Institute of Chemical Engineers (IChemE) presented this BP-ICAM research project with the Oil & Gas Award at the global awards in Manchester in November 2016, recognising it for ‘innovation in the oil and gas sector, efficient energy use or the development of energy production methods that reduce energy intensity’.
Henna - not just for hair and hands
It’s more common to associate the henna plant with temporary tattoos or hair dyes, but the University of Illinois team selected it for their research into corrosion for another purpose - because it is a naturally ‘green’ inhibitor. The leaves of the plant contain a reddish-orange dye called Lawsone, an agent also known as hennotannic acid, which has been known to inhibit corrosion.
