Intermetallic particles trigger streaking corrosion in AA7075-T6

Abstract

Streaking corrosion (SC) of AA7075-T6, characterized by the rapid dissolution of an altered surface layer (ASL) formed through mechanical surface treatments, is investigated. Utilizing in situ high-resolution reflected light microscopy, we reveal that SC initiates preferentially on intermetallic particles (IMP) or pre-existing pits. Optical evidence of galvanic interactions between propagating streaks and connected IMPs is observed. Concurrent in situ open circuit potential (OCP) measurements show a characteristic pattern that correlate with SC initiation, progression, and termination. This work demonstrates the effectiveness of a simple in situ optical-electrochemical setup in tracking dynamic local corrosion processes and directly linking OCP transients to specific corrosion events.