Enhanced Long-Term Reliability of Seal DeltaSpot Welded Dissimilar Joint between 6061 Aluminum Alloy and Galvannealed Steel via Excimer Laser Irradiation.

Structural-adhesive-assisted DeltaSpot welding was used to improve the weldability and mechanical properties of dissimilar joints between 6061 aluminum alloy and galvannealed HSLA steel. Evaluation of the spot-weld-bonded surfaces from lap shear tests after long-term exposure to chloride and a humid atmosphere (5% NaCl, 35 °C) indicated that the long-term mechanical reliability of the dissimilar weld in a corrosive environment depends strongly on the adhesive-Al6061 alloy bond strength. Corrosive electrolyte infiltrated the epoxy-based adhesive/Al alloy interface, disrupting the chemical interactions and decreasing the adhesion via anodic undercutting of the Al alloy. Due to localized electrochemical galvanic reactions, the surrounding nugget matrix suffered accelerated anodic dissolution, resulting in an Al6061-T6 alloy plate with degraded adhesive strength and mechanical properties. KrF excimer laser irradiation of the Al alloy before adhesive bonding removed the weakly bonded native oxidic overlayers and altered the substrate topography. This afforded a low electrolyte permeability and prevented adhesive delamination, thereby enhancing the long-term stability of the chemical interactions between the adhesive and Al alloy substrate. The results demonstrate the application of excimer laser irradiation as a simple and environmentally friendly processing technology for robust adhesion and reliable bonding between 6061 aluminum alloy and galvannealed steel.

Randomized controlled pilot study of the preoperative use of brimonidine 0.33% topical gel for hemostasis in Mohs micrographic surgery.

BACKGROUND: Brimonidine topical gel may be useful in cutaneous surgical procedures because of its vasoconstricting properties. OBJECTIVE: Assess the hemostatic effect of topically applied brimonidine in patients being treated with anticoagulants and undergoing Mohs micrographic surgery (MMS). METHODS: Subjects undergoing MMS were randomly assigned to the control (n = 10) or study arm (n = 14). Controls received standard-of-care MMS, whereas the study arm received the same and preoperative application of brimonidine. Evaluations included rate of blood flow, percentage of wound bed surface area needing electrocautery, and changes in skin colorimeter readings. RESULTS: The treatment arm had 68% less blood loss over 30 seconds versus the control arm (P < .05). No patient in the brimonidine arm had more than 50% of the wound bed cauterized versus 80% in the controls. Erythema in the treatment arm was decreased by 3.89 times (P < .01) versus in the control arm. LIMITATIONS: Limitations were small sample size; sites limited to the face; the fact that measurement of bleeding did not account for anesthetic mixed with blood; visual estimation of percentage of wound surface area requiring cauterization; and no measurement of volume of anesthesia, wound depth, or postoperative complications. CONCLUSION: Preoperative application of brimonidine 0.33% gel may help decrease blood loss and the need for electrocautery during MMS for patients taking anticoagulants.