Environmental effects in fatigue crack initiation and propagation
The aim of this project is to examine the effect of environment (seawater with or without cathodic protection) on crack initiation and incipient slow growth. The steel used is BS 4360 - 50D. Results show that cathodic protection can increase the number of cycles to initiation, compared to air values. This is explained by the plugging effect of deposition of Ca and Mg. After initiation, the same deposition products can retard or even stop crack growth. EDAX-analysis of the deposition products shows that at potentials higher than -900 mV SCE the deposition products are rich in Ca, while the products are rich in Mg at potential at -1000 mV SCE or lower. The change in the composition of the deposition products together with the increasing hydrogen uptake at decreasing potentials explains why the longest lives are found at potentials of -1000 mV SCE. When tests are performed at 1.0 Hz instead of 0.1 Hz, differences are observed due to the fact that the precipitation rate of CaCo(3) and Mg OH(2) is governed by the cathodic current density and is therefore strongly dependent on the potential.
Bibliographic Reference: EUR 12205 EN (1990) 70 pp., MF, ECU 4
Record Number: 199010382 / Last updated on: 1994-12-01
Original language: en
Available languages: en