THE THEORETICAL ANALYSIS OF GALVANIC CORROSION (Zn, Fe and Cu) UNDER ACTIVATION CONTROL

number: 
2276
English
Degree: 
Author: 
Aseel Fadhil Khudair
Supervisor: 
Dr.Basim O. Hasan
year: 
2009

 For the increasing importance of corrosion in all branches of recent life, a study on behavior of widely industrial metals (zinc, iron and copper) in deaerated hydrochloric acid is presented in this thesis. This work was developed to predict the corrosion rate and corrosion potentials of binary and ternary metal system to investigate and discuss the effect of temperature, concentration and area fraction of metals on the corrosion rate and corrosion potential. Metals used were iron, copper and zinc. First the corrosion of these metals was theoretically studied and compared with experimental work and then the same analysis is held down the present study to explain the free corrosion of each metal, galvanic coupling and ternary galvanic system of these metals.The analysis were performed for pH=0.7,temperatures of 30, 45 and 60oC and for area ratios of 0.5, 1 and 2 for comparison with experimental work. The other analyses were for pH range of 1-3, temperature range of 20-60 and various area fractions of the used metals. It was found that the calculated results is close to experimental results, and the galvanic coupling increases the corrosion rate of the anodic (active) metal over that if it was under free corrosion condition, and the ternary system has the highest corrosion current. In all conditions the trend of calculated results is as follows: an increase in temperature increases the corrosion current but decreases the corrosion potential at constant pH value. Increasing pH increases the corrosion potential but decrease the corrosion current when fixing temperature. The area fraction had a noticeable effect on the galvanic corrosion rate and alvanic corrosion potential where as the area fraction of more noble metal increases the corrosion potential increases and the corrosion current increases. In ternary galvanic system, zinc had act as a sacrificial anode and protectiron and copper which act as a cathode.