Effect of Storage Conditions on the Corrosion Resistance of Laser-Treated Al Surfaces Discussed in Terms of Adhesive Bond Strength
Authors: Hirakawa Rio , Terasaki Nao , Gundlach Christian , Hartwig Sven 
Published: December 2024

In the automotive industry, structures and components are becoming increasingly multi-material. Materials such as steel, aluminum, and carbon fiber composite materials, among others, are used in a composite manner to improve the mechanical utility and performance of each component.

The most traditional technique for assembling dissimilar materials is mechanical fastening. However, mechanical fastening requires numerous manufacturing processes, affects the inherent mechanical properties of the base material, and increases weight due to extra metal parts. Adhesive bonding is increasingly being used in more and more industrial fields as a method that avoids the above drawbacks.

One disadvantage of adhesive bonding is the long-life durability of the joint when exposed to harsh conditions such as the presence of water or corrosive environments[1]. To ensure this long-life durability of the joint, surface pretreatment of the material is always necessary. Among the many surface pretreatments, laser surface treatment is an efficient method that corrects both the physical and chemical properties of the surface at once, with numerous advantages such as requiring only electrical energy, being easy to integrate into the production process, and not using chemicals.

Laser surface treatment of aluminum alloys has been shown to improve the durability of joints through the formation of passivation oxide films and roughening of the material surface[2,3,4]. The laser-treated aluminum alloy surfaces are expected to undergo physicochemical changes over time due to absorption of moisture and organic compounds in the storage atmosphere as well as storage temperature, and the above anticorrosion effects of laser treatment are expected to change as well. In industry, material surfaces are subjected to a certain storage period after laser treatment before they are joined, but the effects of storage methods on the corrosion of treated surfaces and joint interfaces have not yet been fully investigated.

In this study, laser-treated aluminum alloys were stored in a high-temperature, high-humidity environment, then joined and DCB tests were performed to investigate how the corrosion protection effect on the material surface given by the laser treatment changed during storage and how it affected joint strength. The storage period was varied from none to one month, and the results of indoor storage are also shown for comparison. Through the above, the appropriate storage environment and storage period after laser treatment will be discussed.

This presentation is based on results obtained from a project, JPNP2005, commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

[1] Johannes M. C. Mol, “Interface strength and degradation of adhesively bonded porous aluminum oxides,” npj Materials Degradation, Volume 1, Article number 8, 2017, DOI: 10.1038/s41529-017-0007-0

[2] Elisabeth Stammen, “Surface Modification with Laser: Pretreatment of Aluminium Alloys for Adhesive Bonding,” Tenth International Conference on Plasma Surface Engineering (PSE2006), Volume 4, Issue S1, Pages S39-S43, 2007, DOI: 10.1002/ppap.200730303

[3] Rico Rechner, “Influence on the strength and aging resistance of aluminium joints by laser pre-treatment and surface modification,” International Journal of Adhesion and Adhesives, Volume 30, Issue 7, Pages 595-601, 2010, DOI: 10.1016/j.ijadhadh.2010.05.009

[4] Jianping Lin, Junying Min, “Effect of laser ablation treatment on corrosion resistance of adhesive-bonded Al alloy joints,” Surface and Coatings Technology, Volume 345, Pages 13-21, 2018, DOI: 10.1016/j.surfcoat.2018.03.087