Abstract
Objective:In this study, electrochemical measurements were used to characterize Anhydrous Tricalcium Phosphate (ATP) as a corrosion inhibitor for mild steel in 1.0 M HCl.Method:The potentiodynamic polarization curves indicated that the ATP reacts as an anodic type inhibitor. In addition, it has been found that the electrochemical impedance confirms the inhibitor character of ATP obtained by the potentiodynamic polarization curves where the inhibition efficiency increases by its concentration to reach a maximum of 93.79 % at 10-4M. The temperature solution influence indicated that the corrosion rate increases with temperature while the inhibitor acts actively. Thermodynamic adsorption and activation parameters indicated that the ATP acts by physical adsorption on the metallic surface with an endothermic process of metal dissolution.Result:Additionally, it was found that the adsorption of ATP molecules obeyed to the Langmuir isotherm. Surface analyses via scanning electron microscopy (SEM) was used to investigate the morphology of mild steel before and after immersion in 1.0 M HCl solution without and with 10-4M of ATP. It is revealed that the ATP acted by the formation of a protective layer on the mild steel.
Highlights
Acid solutions are widely used to eliminate unwanted rust in metalworking, cleaning boilers and heat exchangers
With respect to the environment, the Anhydrous Tricalcium Phosphate (ATP) is favorable to be used in place of some toxic organic inhibitors in agreement with the new environmental limits [11, 12]
The same conclusion was found in our previous study, when we studied the interaction between hydroxyapatite molecules and mild steel in 1.0 M HCl [9]
Summary
Acid solutions are widely used to eliminate unwanted rust in metalworking, cleaning boilers and heat exchangers. The best inhibitors which can be adsorbed on the metallic surface contain in their structures heteroatoms such as oxygen, nitrogen, phosphorus and/or triple bonds [5 - 8]. In the literature, many phosphate derivatives have been investigated as corrosion inhibitors and it has been found that they are excellent corrosion inhibitors [9, 10]. The inhibition property of the phosphocalcic compounds is certified to their pairs and planarity of free electrons in oxygen and phosphorus. The anhydrous tricalcium phosphate derivatives are considered as non-toxic substances. With respect to the environment, the Anhydrous Tricalcium Phosphate (ATP) is favorable to be used in place of some toxic organic inhibitors in agreement with the new environmental limits [11, 12]. The force of its adsorbed layer on metallic surface, according to the Langmuir isotherm, was associated to the functional groups of the aromatic ring [13]
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