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الثلاثاء، 25 مارس، 2014

Diffusion Controlled Impingement Corrosion of some Metallic Fittings

Title:   Diffusion Controlled Impingement Corrosion of some Metallic Fittings
Author         Mohamed Ahmed Fouad Mohamed
Collection   Ph.D. Chemistry 
Abstract:  
Impingement corrosion of 90 copper elbow has been investigated in relation different parameters. Rate of corrosion was expressed in terms of mass transfer coefficient. The following conclusions Mass transfer coefficient increases as solution velocity increases and decreases as rid increases. The dependence of mass transfer coefficient on Sc varies according to the range of Sc considered. Activation energy calculation reveals a value of 8.96 kCal /mol and 1l.5” kCal/mol for low and high range of Sc respectively. Mass transfer data have been these ocorrelated using dimensionless analysis for different ranges of Sc.  Dimensionless equations may be useful for the 90 copper elbow at different conditions. Flow inside 90 elbows enhances the rate of mass transfer by a factor ranges from 1.65 to 26.2 relative to flow inside straight tube which is a strong function of elbow diameter. Addition of polyethylene oxide as drag- reducing polymer inhibits the impingement corrosion rate in 90 copper elbow by 28% to 62% depending on operating conditions. The presence of suspended solids in the solution increases the impingement corrosion rate in 90 copper elbow by 3 to 13%. Scanning electron microscopy (SEM) study on the corroded copper elbow show that maximum rate of corrosion occurred at the stagnation point. Diffusion controlled impingement corrosion of 90° stainless steel elbow depends to a great extent of surface passivity. Failure analysis of 90 copper elbow shows that fracture started III the stretched portion of the piping elbow wall. In the presence of two phase flow, the increase of mass transfer coefficient depends on the gas velocity. Further study in needed to study the effect of different elbow angles.

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