INHIBITION OF GALVANIC CORROSION BY PHENYLTHIOUREA UNDER FLOWING CONDITIONS IN HYDROCHLORIC ACID SOLUTION

إنجليزية
number: 
1833
Degree: 
Author: 
SHAKER SALEH BAHAR AL-KELABY
Supervisor: 
Prof. Dr. Q. J. M. Sulaiman
year: 
2007

Because of the practical importance of galvanic corrosion arises the need to study the effect of corrosion inhibitors, area ratio of cathode to anode (Ac/A), rotational velocities of specimens on galvanic corrosion of several industrially important metals and also to follow the behavior of corrosion rate. The use of weight loss technique is adopted as indicator for performance efficiency of the inhibition process.a Corrosion cell has been designed to measure current and potential versus time for the coupled metal.The performance of galvanic corrosion process has been tested for four major factors that affect the process.

1- Type of metals, copper, carbon steel, and zinc has been chosen.
2- Four area ratios of more noble to less noble metal (Cu/Fe,Cu/Zn and Fe/Zn) are (0.25, 0.5, 1 and 2).
3- Four rotational velocities, 0, 500, 1000 and 1500 RPM.
4- Five phenylthiourea (PHTU) inhibitor concentrations are selected to be 0, 0.001, 0.05, 0.1 and 0.15g/L in air-saturated 0.1N HCl solution at 40oC.In this study we found that corrosion rate increased in
correspondence to the increasing of rotational velocity, while PHTU leads to very low corrosion rate. Efficiency of PHTU anticorrosion effect may approach to 99%. Galvanic factor (GF), galvanic current, potential difference and dissolution current (I) have been studied in most of the cases.Current and potential have been checked out for copper / carbon steel couple together. We found that the potential of either one of them approach the value of the other, which is in range of their values, when they are separated.Current value has been calculated, in condition of zero ammeter resistance for certain parameters. This value was very small in comparison with practical results.Generally, results showed that corrosion potential is more negative with increasing rotational velocities (U) and area ratio (AR), while it is shifted to less negative with increasing PHTU concentration (C).The occurrence of the galvanic corrosion was efficiently verified during the experiments using the following equation given by West:
 
 

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