The growth mechanism and properties of the oxide films on aluminium and 8090 Al-Li-Cu-Mg alloy were studied in simulated acid rain (pH 4.5) by electrochemical techniques, cyclic voltammetry and electrochemical impedance spectroscopy. The potentiodynamic formation of anodic oxide film on aluminium and 8090 Al-Li-Cu-Mg alloy surfaces were described in terms of high field model. This is justified by the obtained values of kinetic parameters: the electric field strength (~10 6 V cm –1 ), ionic conductivity through the film (~10 –12 S cm –1 and 10 –13 S cm –1 ) and half jump distance (~0.150 nm). The impedance data shows that protective passive oxide film on aluminium and Al-Li-Cu-Mg alloy can be formed spontaneously at the open circuit potential in the studied solution with a high resistance (119 k cm 2 for Al and 144 k cm 2 for Al-Li-Cu-Mg alloy). Both electrochemical techniques revealed that the oxide film on Al-Li-Cu-Mg alloy has better protective properties than pure aluminium. The concentration of the metallic ions released into solution from aluminium and Al-LiCu-Mg alloy and measured by atomic absorption spectroscopy was in accordance with the results obtained from the electrochemical techniques.

Circuit Breakers are one of the most important elements in the transmission and distribution of electrical energy, and assessing their condition is of the upmost importance regarding the health and safety of the transmission and distribution system. Numerous procedures and parameters exist that directly reflect the state of the circuit breaker, but this paper focuses on a relatively new procedure that measures and estimates the states of the arcing contacts of the circuit breaker. The state of the arcing contacts is in a direct correlation with the health of the circuit breaker and it is assessed by applying test called the Dynamic resistance measurement. The important parameters during this Dynamic Resistance test will be explained. The results obtained using developed algorithm are demonstrated in the field on a real circuit breaker, completing thus all necessary steps for the assessment of the arcing contacts.