The Role of Cavitation in Improving Coating Corrosion Resistance

Cavitation helps give coatings improved corrosion resistance

A recent study led by a researcher from Tokyo Metropolitan University has introduced a novel method for coating magnesium alloys to enhance their corrosion resistance. Unlike traditional vacuum-based coating techniques that are expensive and time-consuming, the team utilized a liquid-based chemical conversion coating process with the incorporation of cavitation bubbles. This innovative approach resulted in the formation of a thick coating that significantly improved corrosion resistance to chlorides and mechanical properties of the magnesium alloys. The research team aims to leverage this new technology to strengthen lightweight materials in electric vehicles.

Driving Innovation in Lightweight Materials for Electric Vehicles

As the automotive industry undergoes a significant transformation towards electric vehicles, advancements in materials science play a crucial role in developing lighter materials that can extend the range of electric cars. Magnesium alloys have emerged as a key player in this transition due to their low density. However, concerns regarding their corrosion resistance to chlorides and mechanical properties have posed challenges. While magnesium-based composites have been proposed as an alternative, their high production costs and complex manufacturing processes hinder widespread adoption.

One alternative approach is to apply coatings to conventional magnesium alloys through various plating methods. However, most plating techniques involve the slow deposition of ceramic particles, leading to poor adhesion between the substrate material and the coated layer. Additionally, many plating processes require vacuum chambers and high temperatures, making them impractical for magnesium alloys with low melting points.

Advancing Coating Technologies for Magnesium Alloys

Assistant Professor Masataka Ijiri and his team at Tokyo Metropolitan University explored the use of chemical conversion coating, which involves exposing surfaces to a liquid for coating application. While liquid-based methods offer cost and efficiency advantages over plating, they often result in thin coating layers with limited corrosion resistance. Through experiments conducted using water and phosphoric acid, the researchers discovered that introducing cavitation at the surface – the formation and collapse of bubbles – facilitated the formation of thick and uniform magnesium phosphate films.

Two cavitation-based methods, water jet peening and multifunction cavitation combining water jets with ultrasound waves, demonstrated superior coating properties compared to liquid treatment alone. The enhanced coatings exhibited significant improvements in corrosion resistance to chlorides, as validated through electrochemical tests.

Future Implications for Electric Vehicle Materials

While utilizing entire magnesium composite parts may yield favorable outcomes, the high cost associated with such parts necessitates a more cost-effective approach. The team’s technology offers a promising solution for selectively and precisely applying coatings to affordable magnesium alloys, paving the way for enhanced materials in the next generation of electric vehicles.

This groundbreaking research was supported by the Light Metal Educational Foundation and the Proterial Materials Science Foundation.