Industry Insights · Technology · Sep 27, 2026

Atmospheric Pressure Plasma Surface Treatment — Reducing Pretreatment Chemicals and Wastewater, and Industrial Applications

Atmospheric pressure plasma is a dry pretreatment technology that removes organic contamination from metal surfaces and makes them hydrophilic without vacuum equipment. This article summarizes academic findings on cleaning and activating aluminum and their significance for reducing wet pretreatment chemicals and wastewater.

Anodizing pretreatment is fundamentally a wet process in the sequence degreasing → etching → desmutting (Bonnell Aluminum). Each step consumes acid or alkaline chemicals and rinse water, and the resulting wastewater is subject to wastewater discharge facility management under the Water Environment Conservation Act. Atmospheric pressure plasma is attracting attention as a technology that can replace or supplement the organic contamination removal (degreasing) and surface activation steps with a dry process.

Principle

At atmospheric pressure, partially ionizing gases such as air, nitrogen or oxygen by dielectric barrier discharge (DBD), plasma jets or microwave discharge generates reactive oxygen species and ultraviolet light. These decompose and volatilize the hydrocarbon contamination layer on the surface and introduce hydroxyl groups (OH), lowering the contact angle. No vacuum chamber is required, so the technology is easy to integrate into in-line equipment, and treatment times are short, on the order of seconds.

Academic Findings

Bónová et al. (Applied Surface Science, 2015) treated flat aluminum with air and oxygen plasma using diffuse coplanar surface barrier discharge (DCSBD) and reported a sharp decrease in contact angle and reduced surface carbon contamination.
A follow-up study by the same group (J. Vac. Sci. Technol. A, 2020) cleaned and activated aluminum surfaces with 2.45 GHz atmospheric pressure microwave plasma and emphasized that the method generates no chemical waste.
Cuao Moreu et al. (Materials, 2026) applied an atmospheric pressure plasma jet to 6061 alloy and reported that the resulting passive layer showed higher corrosion resistance than untreated material, with polarization resistance increasing by about three orders of magnitude.
Červený et al. (Int. J. Adv. Manuf. Technol., 2025) compared mechanical methods, chemical degreasing and other aluminum pretreatments before adhesive bonding and summarized the effects of surface cleanliness and wettability on joint strength.

Significance for the Surface Treatment Industry

Chemical reduction: Removing organic contamination with plasma reduces the load on alkaline degreasing baths, lowering replacement frequency and chemical consumption.
Wastewater reduction: Lower water use in the degreasing and rinsing steps is favorable in calculating the maximum daily wastewater volume and reduces the burden of treating oily wastewater.
Quality: In anodizing pretreatment, where passing the water-break test is a prerequisite, the uniform hydrophilic surface after plasma treatment favors coating uniformity.
Limitations: Plasma cannot replace oxide film removal or smut removal, so the etching and desmutting steps remain wet. The treatment effect also decreases over time (aging), so the interval before subsequent processes must be controlled.

Forms of Application

Industrial applications are currently most advanced in activation before bonding and painting, cleaning of electronic components and pretreatment before printing. For anodizing and chemical conversion coating pretreatment, adoption is at the review stage as a degreasing aid or for selective cleaning. EF Technology holds a registered patent related to plasma pretreatment and is reviewing its scope of application with the aim of reducing wet pretreatment chemicals and wastewater.

References

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