Influence of the Carrier Gas on Powder Coating Efficiency

Insights from an academic case study on architectural applications

An academic study conducted within the framework of a Master’s thesis in Management Engineering at the University of Rome Tor Vergata investigated the influence of the carrier gas on powder coating performance.The research compares compressed air and nitrogen as carrier gases in electrostatic powder coating, focusing on architectural components such as aluminum profiles and flat steel samples.

The experimental activities were carried out in university laboratories using pre-treated laboratory samples, with industrial validation supported by two Italian coating companies.

Objective of the Study

The primary objective of the research was to evaluate and quantify the benefits of electrostatic deposition using nitrogen as a carrier gas, replacing compressed air, in powder coating applications.

The evaluation focused on the following parameters:

• surface finish and film distension

• penetration and coverage of complex geometries

• coating thickness distribution

• gloss levels

• process stability related to temperature and humidity conditions

Methodology

The study compared two coating processes:

• powder coating with compressed air as carrier gas

• powder coating with nitrogen as carrier gas

Mechanical, tribological, and aesthetic characterizations were performed, including:

• scratch resistance tests

• wear resistance tests

• thickness measurements

• gloss evaluation

• Faraday cage penetration analysis

Key Findings – Mechanical and Tribological Performance

From a mechanical standpoint, the study reports that coatings applied with compressed air showed slightly higher micrometric resistance in scratch and wear tests. In long-distance tribological tests, the volume of material removed from air-applied coatings was approximately 31% lower compared to nitrogen-applied coatings.

This confirms that traditional air-based application can offer advantages when resistance to mechanical stress is the primary requirement.

Key Findings – Aesthetic Profile and Film Behavior

Significant differences emerged in terms of coating behavior and aesthetic profile:

• Thickness distributionNitrogen-based coating showed a higher percentage of samples within the reference thickness range, with the ability to effectively coat substrates using thinner and more uniform films.

• GlossFor glossy finishes, nitrogen-applied samples exhibited a higher absolute gloss value (+2 GU).For matte finishes, this increase in gloss was identified as an undesirable effect.

• Film distension and surface uniformityNitrogen application resulted in improved film distension, contributing to smoother and more uniform surfaces.

Faraday Cage Effect and Complex Geometries

One of the most relevant findings concerns the Faraday cage effect.The study shows that nitrogen as a carrier gas contributes to better penetration and coverage of complex geometries, such as corners and shadow areas typical of architectural profiles.

The analysis of thickness delta (Δ) demonstrated that lower thickness variation (<10 µm) correlates with easier coating of complex shapes, a condition more consistently achieved with nitrogen.

Conclusions

The study concludes that:

• nitrogen as a carrier gas provides tangible benefits within a clearly defined operating range

• traditional compressed air performs better under certain mechanical stress conditions

• nitrogen offers qualitative improvements in:

  • film distension

  • thickness uniformity

  • coverage of complex geometries

  • electrostatic field containment

These results confirm that nitrogen-assisted powder coating can enhance process quality and control, particularly in architectural applications where geometry and aesthetic consistency are critical.

Source

This article is an extract from an academic thesis published in Verniciatura Industriale, Issue 672 (April 2024).

📄 The full article is available for download as a PDF.