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59 NACE INTERNATIONAL: VOL. 56, NO. 11 MATERIALS PERFORMANCE NOVEMBER 2017 The effects of hydrogen charging on the electrochemical corrosion behavior of vari- ous aging states of 7050 aluminum alloy were investigated by cathodic hydrogen- permeation and electrochemical testing. Experimental Procedures Material and Heat Treatment The composition of the 7050 aluminum alloy used was 6.42 wt% Zn, 2.25 wt% Mg, 2.02 wt% Cu, 0.13 wt% Zr, 0.03 wt% Ti, 0.10 wt% Mn, 0.04 wt% Cr, 0.11 wt% Fe, 0.07 wt% Si, and the balance Al. The 7050 aluminum alloy was supplied by Alcoa Corp. in the form of smooth specimens machined from 55-mm thick wrought aluminum plates. The specimens used for the electrochemi- cal tests were rectangular blocks measur- ing 10 by 10 by 2 mm. All specimens were treated as follows: solution treatment for 2 h at 470 °C; water quench; then artificial aging for 8, 16, or 24 h at 135 °C. Cathodic Hydrogen Charging Hydrogen was introduced into the alu- minum specimens by electrolytic cathodic hydrogen charging. This procedure was p er for m ed at ro om t emp erature in a 1 mol/L sulfuric acid (H 2 SO 4 ) solution with arsenic trioxide (As 2 O 3 ) added as the hydro- gen recombination inhibitor. Prior to elec- trolytic cathodic charging tests, the 7050 aluminum alloy specimens were polished with SiC paper. Specimens were precharged with a current density (CD) of 20 ±1 mA/ cm 2 using platinum anodes. Charging times varied from 6 to 24 h. The hydrogen content in the specimens was analyzed by an EMGA-621 † hydrogen determinator. Electrochemical Testing Electrochemical tests were carried out immediately after charging to minimize the loss of hydrogen . Th e specim ens were mounted with epoxy resin to provide an exposed area of 100 mm 2 and polished with successively finer SiC paper. The specimens were then rinsed with deionized water, † Trade name. FIGURE 1 Hydrogen concentration in 7050 aluminum alloys under various aging states and different charging times. FIGURE 2 Polarization curves of 7050 aluminum alloy: (a) underaged state, (b) peak-aged state, and (c) over-aged state.