A study of galvanic corrosion between carbon fibre reinforced PA6 composites and metals under dry sliding conditions

Abstract

In the present work, continuous carbon-fibre reinforced polyamide 6 (CCF/PA6) composites were manufactured by fused deposition modelling technology and their tribological behaviour was studied on a pin-on-disc configuration under room conditions. The results showed that galvanic corrosion could take place between the fiber and steels even under nominally dry contact conditions. The severity of the corrosion process is dependent on fibre orientation, environment humidity and the type of counterpart materials. In particular, the specimens with normal fibre orientation (perpendicular to the sliding direction) showed higher values of galvanic current and wear loss than those with parallel fibre orientation (parallel to sliding), especially under high pressure conditions. For instance, with normal fibre orientation against steel counterparts, the specific wear rate of printed CCF/PA6 increased abruptly from 5.32 × 10⁻⁶ mm³ N⁻¹ m⁻¹ at 1 MPa to 12.33 × 10⁻⁶ mm³ N⁻¹ m⁻¹ at 2 MPa; by contrast, a parallel orientation showed only a modest increase, from 1.98 to 2.45 × 10⁻⁶ mm³ N⁻¹ m⁻¹ over the same pressure span. Further, the galvanic current increased with humidity, nearly doubling from 20 % to 80 % RH. However, such a corrosion effect was not observed against titanium counterparts, which may be due to the inherent stability of titanium. These findings highlight the importance of galvanic corrosion for understanding the wear behaviour of carbon fiber reinforced polymers, as well as the design and selection of tribological materials from a systematic point of view by considering the complexity and interconnectedness of the tribological system.