The Study On Galvanic Corrosion Protection And Its Durability Of Bond-Riveted Joints In AA5083/C_f/Epoxy Laminate

AA5083/C_f/Epoxy(CARALL)fiber metal laminates have great application prospects in offshore engineering structures due to their high modulus and fatigue resistance.However,the tendency of galvanic corrosion at mechanical bonding greatly limits the development of such materials.The use of the bond-riveted structure can effectively improve the safety performance and corrosion resistance at this joint,while the adhesive failure is considered a key issue of the bond-riveted structure exposed to the chlorides.To this scope,polyaniline(PANI)modification of epoxy adhesive was utilized to study the galvanic corrosion resistance and durability of bond-riveted joints of CARALL laminates and AA5083/CFRP in the marine environment.Moreover,the effect and mechanism of polyaniline modification on corrosion of joints were discussed in this paper.Through finite element simulation,it was found that the the corrosion reaction region was migrated by the addition of adhesive,which ensured the inert nature of the metal surface and reduced the electrochemical activity inside the system.Meanwhile,the corrosion tendency caused by the potential difference of the internal component electrode was weakened through the existence of adhesive.In addition,the current concentration at the aluminum rivet/carbon fiber interface was reduced due to the polyaniline modification.Which contributed to the reduction of possibility of corrosion current breakdown and inter-plate interface peeling.Based on the results of finite element simulation,the optimal coating ratio was determined by open circuit potential and water absorption test.The electrochemical test of the optimized parameters showed that the Epoxy/PANI layer had better corrosion resistance and durability in 3.5 wt%NaCl solution.Moreover,the reverse electric field was generated on the polyaniline surface,which canceled part of the polarization current and weakened the adverse effects caused by the alternating current between Al/CFRP.The surface investigation indicated that polyaniline filled the defect generated by the thermal curing process of the resin surface.Besides,the adhesive modification improved the compactness of the adhesive layer structure and significantly enhanced its shielding effect on Cl-in the medium.The results of salt spray and seawater immersion test showed that the Epoxy/PANI adhesive had a reduction of merely 32%in interface strength after prolonged environmental corrosion(1 month).Compared with Epoxy under the same conditions,the durability of the adhesive layer was improved over 50%.Moveover,the aluminum rivet under the action of Epoxy/PANI in the CARALL laminate had a strength retention rate of over 92%after 60 days of seawater corrosion.Even in the AA5083/CFRP joint,which was more sensitive to galvanic corrosion,the strength retention was still as high as 82.2%after 60 days immersion.Combined with the corrosion morphology analysis,the aggregation of corrosion products at the end of AA5083/CFRP was effectively reduced with Epoxy/PANI adhesive.Moreover,the honeycomb pitting corrosion morphology did not appear in rivet under the protection of modified adhesive,which greatly avoided the occurrence of galvanic corrosion at the interface.