Research team develops protective coatings using atmospheric-pressure plasma

Illinois Applied Research Institute (ARI) researchers Dr. Dan Krogstad and Dr. Maryam Eslami along with Prof. Mohan Sankaran (PI) in the Nuclear, Plasma, and Radiation Engineering (NPRE) Department have recently completed a successful project on the development of atmospheric-pressure plasma as a chemical waste-free method to deposit protective pretreatment coatings on steel. This two and a half-year project was funded by the US Army Engineer Research and Development Center (ERDC) and managed by Dr. Rebekah Wilson at the Construction Engineering Research Laboratory (CERL).

Corrosion remains a significant problem for the Department of Defense (DoD), costing billions of dollars annually for corrosion-related maintenance, remediation, and prevention. Corrosion prevention is the most cost-effective approach and typically requires the use of a multilayer coating systems consisting of a paint, a primer, and a pretreatment (conversion) layer. However, many of the pretreatment methods are highly hazardous to human health and the environment.

In this work, we developed a method to deposit the conversion coatings without the generation of hazardous chemical waste. Atmospheric pressure plasma is a method that uses microwaves to excite a carrier gas to create a plasma. In our project, we used this plasma to interact with and excite an organometallic precursor to break apart the molecule into individual atoms, ions, and radicals. These species can then deposit on the surface atom-by-atom and create a ceramic conversion coating on the steel surfaces.

In our project, we were able to optimize the plasma processing parameters to create consistent nanoscale zirconia coatings on steel substrates. We were then able to prove the effectiveness of the coatings using electrochemical corrosion testing. Our results showed that the zirconia coatings can provide corrosion protection to the steel through anodic inhibition. Additionally, we showed that when the plasma deposited conversion coatings are painted with representative DoD architectural paints, the rust creep was significantly reduced during accelerated environmental degradation testing.

This project demonstrated that atmospheric pressure plasmas could be a promising processing technology to obtain low toxicity conversion coatings while minimizing chemical waste.