Comparative Adhesion of Anaerobic and Cyanoacrylate Adhesives to Hydrophilic Surface on Mild Steel

This study is about laser-induced surface activated DC01 and S235 mild steels, which are bonded with an anaerobic acrylic adhesive (Loctite 270) and a cyanoacrylate adhesive (Loctite 496). A fiber laser was used with 50–100% power, 20–200 kHz pulse frequencies, and scanning speeds were 500–2000 mm/s. Wettability was measured by water contact angle (WCA), and the joint performance was examined through single-lap shear tests. Both untreated steels showed hydrophobic behaviour (DC01: 72.9°, S235: 89.8°), which resulted in low shear strengths: 0.29 kN (DC01, acrylic), 2.03 kN (DC01, cyanoacrylate), 0.57 kN (S235, acrylic), and 0.06 kN (S235, cyanoacrylate). After laser treatment, the WCA was under 5° in most cases, showes complete wetting. This change was reflected in a significant increase in strength. In the case of DC01, the acrylic adhesive achieved 2.9 kN (≈10×) and the cy­anoacrylate achieved 5.6 kN (≈2.5×). In the case of S235, the acrylic adhesive achieved 3.9 kN (≈7×), while the cyanoacrylate increased from 0.06 to 6.1 kN (≈100×). Based ont he results the laser activation can create a clean, high­ly hydrophilic surface. It increases the adhesion of both adhesive systems. Al­though the two steels responded differently to the treatment, in all cases the reduction in the rim angle was closely related to the increased bond strength.