Laser pre-treatment for corrosion protection

An interdisciplinary team of scientists at Oak Ridge State Laboratory (ORNL) in the USA is working on laser interference patterning (LIS) as a pretreatment method. The aim is to provide effective and durable corrosion protection for aluminium alloys used in cars and aircraft.

laser pre-treated primer coating
A primer-coated specimen shows marks from the laser system. Photo: Carlos Jones/ORNL

In addition, the process is intended to be an environmentally friendly and health-friendly alternative to conventional, wet-chemical methods. The research project, which will be completed at the end of 2021, was initiated and funded by the US Department of Defence to optimise corrosion protection for military vehicles. The researchers treated sheets of different aluminium alloys with the innovative technology by splitting the primary beam of a pulsed nanosecond laser into two beams and focusing them on the same point on the sample.

Enhanced roughness

This process increased the roughness of the surface by forming periodic structures, changed the surface chemistry as well as the microstructure beneath the surface. As the surfaces are exposed to a lot of energy during the process, one focus of the project was to optimise the parameters to avoid cracks or microstructural effects.

Using X-ray photoelectron spectroscopy, the team investigated the chemical composition of the upper 5 to 8 nanometres of the surfaces. They found that these could be cleaned gently by LIS and also exhibited reliable corrosion protection in almost all primed and painted sheets. In addition, the adhesion properties were not negatively affected, but corresponded to those of the wet chemical pre-treatment.

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