14This work presents the electrochemical evaluation of protective layers generated in a 15 coating defect from lithium-leaching organic coatings on AA2024-T3 aluminum 16 alloys as a function of neutral salt spray exposure time. Electrochemical impedance 17 spectroscopy was used to study the electrochemical properties on a macroscopic 18scale. An electrochemical model allowed to quantitatively link the electrochemical 19 behavior with the physical model of the layer in the damaged area as studied by 20 scanning electron microscopy. Local potentiodynamic polarization curves obtained 21 from micro-cell measurements showed an increase of the passive range in the defect 22 area due to the formation of a robust protective layer. Scanning vibrating electrode 23 technique measurements confirmed the non-reversible long-term corrosion protection 24 of these generated layers in the coating defect. 25 26

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Efficiency of corrosion inhibitors in aqueous solutions depends on several interfacial parameters, which may vary over time. Therefore, reliable electrochemical techniques are demanded for screening the efficiency of corrosion inhibitors and monitoring their performance over time. Here, we evaluate corrosion inhibition efficiency of imidazole-based compounds on bare Cu surfaces and highlight the importance of electrochemical evaluation of the inhibitor over time, characterized by linear polarization resistance techniques as a reliable, instantaneous and non-invasive method for assessing intrinsic inhibitor performance in lab screening studies.

In this paper, different macroscopic electrochemical techniques are applied to study the corrosion inhibitor efficiency, protection mechanism and stability of a calcium aluminum polyphosphate silicate hydrate inhibitor on hot-dip galvanized steel in the timedomain. Potentiodynamic polarization (PP) measurements are applied to study the anodic and cathodic mechanistic behavior as well as inhibitor efficiencies at discrete and single times of exposure. Open circuit potential (OCP) with superimposed linear polarization resistance (LPR) measurements are applied as a faster, non-invasive alternative to PP, characterizing the overall performance of the system in terms of the polarization resistance. Electrochemical impedance spectroscopy (EIS) measurements are applied to detail both the overall performance of the system as well as the corrosion inhibition mechanism related to the electrochemical system's physicochemical representation over time. Electrochemical noise (EN) measurement are used to evaluate the inhibition efficiency as a function of exposure time, represented by the electrochemical noise resistance. Odd random phase electrochemical impedance spectroscopy (ORP-EIS) is selected as the electrochemical tool to study the system's instability, by evaluation of the non-linearities and non-stationarities over time. The non-stationarities present in the inhibitor-containing electrochemical system are shown to cause the overall instability of the system and should be taken into account when interpreting results from the different techniques over time.

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