الفهرس 
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Abstract
The effect of varying of the surface roughness on pitting, galvanic corrosion and corrosion fatigue of a 316 stainless steel in 3 % Na CI solution at room temperature and at 850C was investigated. The effect of high temperature aging on the fatigue behavior of a 316 stainless steel in air at room temperature and in a 3 % NaCI solution at both room temperature and 850C was investigated.
An apparatus for circulting the aqueous solution was constructed on a pre-existing fatigue testing machine using the Wholer principle for the purpose of corrosion fatigue testing.
The results of the present investigation have indicated that increasing the surface roughness accelerates pitting corrosion. The fatigue resistance of a relatively rough surface is less than the fatigue resistance of smooth surface when tests were carried out in air, but varying the surface roughness did not cause any significant effect on the fatigue life when tests were carried out in 3 % NaCI solution at 350C and at 850C.
It has been shown that a galvanic coupling can be produced when two specimens of the same material but together, having surface roughness are in contact together.
Thus to avoid galvanic corrosion, the two surface must be of the same roughness or separated by using an insulation.
The fatigue resistance of stainless steel in 3 % NAci solution at 350C was found to be significantly lower than in air at room temperature. Raising the temperature of the Asalt solution from 350C t to 85 0C decreased the fatigue life of the steel.
Aging at 6500C for 6.5 hours was found to reduce the fatigue resistance of the steel when tested in the salt solution at 350C and at 850C. The deterioration in fatigue behavior as a result of aging was much less pronounced when tests were carried out in air.
It is proposed that the precipitation of carbides along grain boundaries and formation of chromium depleted regions in the vicinity of the grain boundaries accelerated the process of fatigue crack initiation in the aged specimens.