Experimental Study of 2-Amino-5-( 4-nitrophenyl )-1 , 3 , 4-Thiadiazole for MS in HCl Solution

The present work aims to study the inhibition performance of new organic inhibitor namely ANTD “2-amino-5-(4-nitrophenyl)-1,3,4thiadiazole” on corrosion of mild steel (MS) in HCl environment at the concentration of 1.0 M through using weight loss techniques. Weight lost measurements demonstrates the presence of a film on MS surface in existence of organic substance. The inhibition performance of ANTD at various concentrations for mild steel increases with increasing concentration and with an increased in the immersion time and decreased with raising temperatures degrees. The optimal inhibition efficiency of (ANTD), 82%, was achieved for mild steel when immersed with the highest utilized concentration for 6 hrs. KeywordsMild steel, Corrosion Inhibition, ANTD. How to cite this article: T.K. Abed, Kh.F. Al-Azawi, Sh.H. Jaber, Sh.B. Al-Baghdadi and A.A. Al-Amiery, “Experimental Study of 2-amino-5-(4-nitrophenyl)-1, 3, 4-Thiadiazole for Mild Steel in Hydrochloric Acid Solution,” Engineering and Technology Journal, Vol. 37, Part C, No. 2, pp. 214-218, 2019.


Introduction
Corrosion of mild steel, may cause constitutional damage and produce variations in physical and/or chemical characteristics of the pipes and other manufacturing equipment. These impacts confirm that corrosion could lead to huge loses if an efficient solution is not figured out. Inhibiting corrosion of MS plays a significant role in many products, chiefly in manufacturing industries that deal with chemicals and utilize of MS. Many of investigations have been done to study efficient ways for inhibitive corrosion. Acids are exceedingly utilized in chemical and petrochemical processes, such as pickling, cleaning, descaling, etc. Inhibitors have the ability to reduce the dissolution rate of mild steel [1][2][3][4][5]. Mild steel is widely employed in industry processes and as a result, it is damaged when exposed to different corrosive processes. The usage of inhibitors is the most workable techniques for protection of mild steel and alloys against corrosion, essentially in corrosive solution [6][7][8]. The organic molecules, which are employed as inhibitors, can block the metals from oxidation reaction through a certain mechanism [9]. In continuation of previous studies [10][11][12][13][14][15][16][17][18][19], herein, we investigate the application of inhibitor (ANTD) (Figure 1) as corrosion inhibition of mild steel coupons in an acidic solution by gravimetric analysis.

III. Gravimetric analysis
Gravimetric analysis has been completed utilizing MS specimens in 1 M HCl in the absence and presence of ANTD. The MS specimens were cleaned and weighted and were immersed for 6 h., at temperatures, "303, 313, 323 and 333" K., in presence and absence of ANTD. Then after MS specimens were removed, cleaned the weighted. The losing in weights was calculated via different in weights of MS specimens that exposure and not exposure. The other characters like CR (corrosion rate), θ (MS surface coverage), and η % (corrosion inhibition efficiency) were estimated according to equations 1-3 [21,22].
Where W=loss in weight (mg), A = (cm2), t = time in h, CR=corrosion rate without ANTD and CR(i) with ANTD.

I. Gravimetric techniques
Results of gravimetric for specimen of MS in corrosive media at various concentrations of ANTD starting form 0 mM are presented in Figure 2 that represent the impacts of inhibitor concentrations on CR (A) and θ (B) for MS in 1 M HCl. It is an efficient way to optimize the effects of conc. of ANTD on inhibitive performance [23]. The investigation results indicated such increase of ANTD prevent MS from corrosive and the inhibitive performance increases in parallel with increases of concentration of ANTD, as presented in Figure 3. The inhibitor, 2-amino-5-(4-nitrophenyl)-1,3,4thiadiazole shows inhibition efficiency, (82.0%) at 5x10-1 mM. The excellent corrosion inhibitive performance is imputed to bonding of ANTD molecules with the MS surface, which is confirmed due to heteroatoms "N, O and S" in ANTD molecule and huge molecular structure. In addition, the existence of a benzene group boosts the density of electrons at the efficient center that accelerates the interaction of ANTD with MS [24].

II. Temperature Impacts
Versions of inhibitive effectiveness of (ANTD) on alloy surface in corrosive solution with and without of various ANTD concentrations at temperatures degrees 303K-333K signalize that IE% raise with rising concentration and diminish in parallel with rising temperature degrees (Figure 4). In general, molecules from organic origins have negative absorption and signalize to an exothermic process, so this is why the IE% diminish when the temperature raises.

III. Proposed inhibitive mechanisms
ANTD molecules were adsorbed on alloy and forming a protective layer that bond to the metal surface. The adsorption mechanisms actions of organic molecules as inhibitors for MS could progress through the following ways.

Conclusion
Our work results revealed that ANTD functioned a superior corrosion inhibitor for the surface of mild steel in hydrochloric acid. The superior performance of ANTD at conc. of 5x10-1 mM was 82% but diminished with rising of temp.
Degrees that might propose physio-sorption. ANTD is proved as a superior inhibitor with good inhibitive effects due to havening heteroatoms (S, N and O) atoms.