The corrosion inhibition properties of 8-hydroxyquinoline (8-HQ) in 0.1 M HCl for copper have been investigated by using experimental (electrochemical impedance spectroscopy (EIS), dynamic electrochemical impedance spectroscopy (DEIS), and potentiodynamic polarization) and theoretical methods complemented by surface morphological examination with the aid of scanning electron microscopy (SEM) and electron dispersive X-ray spectroscopy (EDAX). Results obtained from all of these applied techniques are in agreement and demonstrate that 8-HQ inhibited copper corrosion in 0.1 M HCl solution significantly and the inhibition efficiency varies directly with 8-HQ concentration. Potentiodynamic polarization results show that 8-HQ behaved like a cathodic-type inhibitor in the studied system. EDAX results reveal that 8-HQ is most stable and effective at 10 h of immersion time. Inhibition of Cu corrosion by 8-HQ is due to electrostatic interaction between the Cu surface and salt of 8-HQ according to the ΔG ads 0 value and FTIR results. E HOMO , E LUMO , and ΔE values support the proposed physisorption mechanism. SEM and EDAX results confirm the adsorption of 8-HQ molecules on a Cu surface.

Starvation, flooding, and dry‐out phenomena occur in polymer electrolyte membrane fuel cells (PEMFCs), due to heterogeneous local conditions, material inhomogeneity, and uneven flow distribution across the single cell active area and in between the individual cells. The impact of the load level and air feed conditions on the performance was identified for individual single cells within a 10‐cell stack. Analysis of the current density distribution across the active area at the cell level was correlated with electrochemical impedance spectroscopy to enable operando fault diagnostic without any impact of the applied analytical tools on the single cell behavior. Moreover, the combination of both technologies allows in‐depth analysis of fault mechanisms in fuel cell single cells with improved sensitivity. Current density distribution and the quantitative assessment of the performance homogeneity demonstrated high sensitivity to small humidity changes and allow the detection of critical events, such as dry‐out in single cells. Impedance analysis is more sensitive regarding polarization and diffusion limitations and allows detection of cell flooding. The combination of both techniques is required for reliable identification of air starvation faults.

The corrosion inhibition behavior of sodium nitrite (NaNO2) towards pure copper (99.95%) in simulated cooling water (SCW) was investigated by means of electrochemical impedance spectroscopy (EIS) and dynamic electrochemical impedance spectroscopy (DEIS). NaNO2 interferes with metal dissolution and reduce the corrosion rate through the formation or maintenance of inhibitive film on the metal surface. Surface morphologies illustrated that the surface homogeneity increased on adding sodium nitrite. Sodium nitrite’s adsorption on copper surface followed the modified form of Langmuir, Freundlich and Frumkin isotherms. Physiosorption mode was involved in the corrosion protection. Electrochemical results revealed an corrosion resistance of copper increases on increasing the inhibitor concentration. The DEIS results indicated that copper corrosion mechanism could be hindered by 50% even after interval of 24 h by optimum concentration of sodium nitrite. The maximum inhibition was achieved with 2000 ppm of NaNO2. With this concentration, inhibition efficiency of up to 61.8% was achievable.

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