Corrosion Pit Induced Stresses Prediction from SEM and Finite Element Analysis

Abstract

Corrosion damage due to pitting is commonly observed in a wide range of aluminum alloys and structural steels that are being used for aerospace and naval structural applications. In order to better understand the particle-induced pitting corrosion in aluminum alloys, experimental measurements were conducted on aluminum 5059 specimens with UTS of 360–370 MPa to observe the corrosion degradation and pits. Both optical microscopy and SEM of various corroded and sensitized specimens were carried out to see how the pits grow and progress with time. An analysis procedure is developed using CAD and finite element software to predict stresses due to corrosion pits. The results obtained indicate that as the duration of the specimen sensitization increased from 29 days to 50 days, the highest stress levels have increased by about 56%. However, further increase in the sensitization time from 50 to 100 days has very little effect on the stress level. It is possible that the deformation due to the exfoliation of the specimen surface layers or the tearing of the surface layers in and around the pits is so severe that the surface stress has decreased due to material failure by developing cracks.

Keywords:

• Aluminum Alloys
• Finite Element Analysis
• Pit Induced Corrosion
• SEM
• Stresses

The author (Ramana M. Pidaparti) thanks the National Science Foundation for sponsoring this research through grant DMR-0505039 and the author (Appajoysula S. Rao) would like to thank the Heads of Code 61 and 60 of the Naval Surface Warfare Center for providing funding for this modeling effort.