Carbon fiber reinforced plastics (CFRP) are promising lightweight materials for vehicle applications.316L is one of the most widely used types of austenite stainless steels and applied in lots of automotive applications.The existence of crevices will result in galvanic corrosion and crevice corrosion when CFRPs and 316L are directly connected.A crevice former for the galvanic system was therefore designed and applied to evaluate the crevice corrosion behaviors and study the mechanism of galvanic crevice corrosion through several electrochemical techniques in this research.The results showed that the crevice corrosion of galvanic systems grew from crevice mouth to the inside crevice and could be divided into four steps,metastable pitting corrosion at the crevice mouth,initiating step of crevice corrosion,propagating step and ending step of crevice corrosion.Because of the influences of the galvanic system,electrode reaction rates were speeded up and the passivation region was shortened at the initiating stage of crevice corrosion.Corrosion rate was observed to be higher in the galvanic system than that in normal crevice systems.