A NEW APPROACH IN THE MONITORING OF METAL COUPON SUBJECTED AT FATIGUE LOAD IN AGGRESSIVE SOLUTION

Corrosion fatigue (CF) is defined as the sequential stages of metal damage that evolve with accumulated load cycling, in an aggressive environment, and resulting from the interaction of irreversible cyclic plastic deformation with localized chemical or electrochemical reactions. The pitting fatigue corrosion (PFC) is a part of CF that studies the influence of fatigue and aggressive environment on pit creations and crack generation and propagation, up to catastrophic failure. It appears then evident the need to know and understand all phenomena that are involved in pit formation and growth in presence of both an aggressive environment and a cyclic load. Although each single effect of both fatigue and corrosion have been extensively documented for aluminium alloys, their synergic action is not thoroughly understood and it continues to be an area of considerable scientific and industrial interest. Fatigue experiments were conducted on bare AA 2024 T3 aluminium alloy specimens in presence of an aggressive environment consisting of a water aerated solution with 3.5 % of NaCl in weight. The mechanical stress was imposed on simple cantilever beam way in high-cycle fatigue. Strain and Open Circuit Potential (OCP) variations observed as a functions of number of cycles are interpreted as a result, and taking into account, the numerous and complex phenomena occurring as time goes on. The pits birth and their subsequent growth seem to play a significant role as crack initiation and subsequent propagation up to final catastrophic failure.