Investigation of Corrosion Protection of Austenitic Stainless Steel in 5.5 M Polluted Phosphoric Acid Using 5-Azidomethyl-7-morpholinomethyl-8-hydroxyquinoline as an Ecofriendly Inhibitor

Abstract

The use of 5-azidomethyl-7-morpholinomethyl-8-hydroxyquinoline (AMH) as a corrosion inhibitor for AISI 321 stainless steel in 5.5 M polluted phosphoric acid was investigated using the hydrogen evolution technique, linear polarization curves, and impedance spectroscopy. Impedance measurements revealed that the dissolution of AISI 321 in 5.5 M polluted phosphoric acid was controlled by an activation mechanism, unchanged even with the addition of AMH at different concentrations. Polarization results showed that the inhibition ability was enhanced with increasing inhibitor concentration. AMH acted as a mixed-type inhibitor by random adsorption on the alloy surface, whatever the nature of the reaction that is taking place. The adsorption of AMH on the AISI 321 surface was also discussed via the Langmuir adsorption isotherm. The influence of elevating the solution temperature on the corrosion inhibition performance was studied. A quantum chemistry study with the DFT method was also conducted, which supplied a logical and exploitable theoretical explanation of the adsorption and the inhibition action of AMH on AISI 321.

Green inhibitor of carbon steel corrosion in 1 M hydrochloric acid:Eruca sativaseed extract (experimental and theoretical studies)

“…The transition state equation yields the activation entropy Δ S * and the standard enthalpy Δ H *. 93,94 log C.R = Δ S */2.303 R + Δ H */2.303 RT + log( R / Nh )…”

Corrosion inhibition and thermodynamic studies on carbon steel in well water by ethanolic extract of Alpinia officinarum leaves (Lesser galangal)-Zn2+

“…Surface coverage values can be calculated using the WL study (31) . These values are used to identify the nature of the adsorption for combined inhibitor molecules (AO-Zn 2+ ) and a suitable isotherm model to the adsorption process.…”

“…The positive values of E a reveal that a highly adsorption on the CS surface (54) . The values of ∆H indicate that adsorption of AO extract is endothermically on the CS surface (31,53,(55)(56)(57) .…”

“…Therefore, the adsorption behavior of the inhibitor has followed a Langmuir model. All the isotherms are represented by the common form (31,65) .…”

“…Langmuir (29,31,50,53,58) , Flory-Huggins (30,62,63) , EL-Awady (30,63,66) and Temkin (30,61,63) isotherms are expressed by following equations.…”