Exploring complex-forming corrosion inhibitors to reduce stiction in non-asbestos organic friction materials

The increasing adoption of electric and hybrid vehicles (BEVs, HEVs, PHEVs) drives significant changes in braking system design, introducing durability challenges related to corrosion. Specifically, stiction between Non-Asbestos Organic (NAO) friction materials and gray cast iron discs represents a critical issue effecting the braking reliability. This study investigates complex-forming organic corrosion inhibitors, 2,5-pyridinedicarboxylic acid and sodium oxalate, as potential additives to mitigate this phenomenon. First, the inhibition mechanisms were examined by evaluating the corrosion behavior of gray cast iron discs in an electrolyte solution simulating the disc–friction material crevice. In the second part of the study, a dedicated stiction test procedure was employed to reproduce stiction phenomena in a simulated brake assembly. After identifying a friction material formulation exhibiting high stiction susceptibility, the influence of the investigated inhibitors on stiction forces and on the morphological characteristics of both disc and pad surfaces was evaluated by introducing the inhibitors into the electrolyte solution. Based on the obtained results, additional friction material formulations containing sodium oxalate as an additive at different concentrations of 4 and 6%w were produced and experimentally characterized.