An Analysis of a premature fatigue failure of an acid bath mixer's shaft under the combined effects of stresses, stress concentrators & corrosion fatigue : Root causes & Solutions

In most of the metal postprocessing industries dedicated to the strip, wire or sheet coating or painting, one uses to exploit degreasing and rinsing baths in order to insure a higher grip quality of the further coating deposition or paintings. Such kind of devices usually works at average temperatures of 150 [°C] with machines components, such as shafts, partially "embedded" within the highly corrosive media and strongly exposed to acidic vapors and condensates.

This presentation aims to develop here the practical case study of a premature fatigue failure of a processing shaft under the combined effect of corrosion fatigue, high bending stresses and local stress concentrators. After a complete overview of the working conditions, the reactive chemical properties of the media, the material characteristics and the stress distribution within this exposed shaft, it will be make emphasis on some potential preventive solutions put in place to avoid further fatigue failure, stress corrosion cracking and in order to increase the shaft lifetime under operations. Materials solutions will be discussed.