Orthophosphoric acid solutions of sodium orthovanadate, sodium tungstate, and sodium molybdate as potential corrosion inhibitors of the Al2Cu intermetallic phase

Abstract

Orthophosphoric acid solutions of sodium orthovanadate, sodium tungstate, and sodium molybdate are tested as potential corrosion inhibitors of the Al 2 Cu intermetallic phase. Corrosion inhibition is observed for 0.2 M solutions of Na 3 VO 4 and Na 2 WO 4 by increasing the pH to > 2. When the pH is < 2, the aforementioned salts increase the corrosion rate of the intermetallic phase. A 0.2 M solution of Na 3 VO 4 causes the precipitation of vanadium phosphate on the surface of the Al 2 Cu phase at pH = 1.

Pentavalent Vanadium Species as Potential Corrosion Inhibitors of Al2Cu Intermetallic Phase in the Sulfuric(VI) Acid Solutions

“…The value obtained is 482 times higher when compared to theoretical value 20 µF•cm −2 [34]. This is characteristic for highly porous electrodes and is related to their enormous surface area [12,27,33,34].…”

“…This occurs due to strong galvanic coupling between Al 2 Cu and the matrix and local dissolution of the latter [2][3][4][5][6][7][8][9][10]. At the same time, Al 2 Cu itself is susceptible to the selective corrosion in acidic and alkaline solutions [2,3,11,12].…”

Corrosion of structural constituents of 2017 aluminium alloy in acidic solutions containing inhibitors

“…Their Al/Cu atomic ratio decreased from 2 to 1.75–1.6, indicating a frequently observed dealloying. [ 13,20,34 ] The corrosion mechanism, however, is more complicated because also oxygen and tungsten were detected on their surface (Figure 10). XPS analysis confirmed the presence of a small amount of W(VI), Cu and O(II).…”

“…[ 9 ] Heteropolyoxovanadates inhibit the corrosion of Al 2 Cu intermetallics due to the precipitation of a protective layer of vanadium phosphate. [ 12,13 ]…”

“…[4][5][6][7]11] Recently, it was shown that heteropolyoxomolybdate species, when adsorbed onto a metallic surface, inhibit anodic reaction in the corrosion cell, whereas heteropoly blue formation is detrimental. [7] The most important heteropolyoxotungstate is [PW 12 O 40 ] 3 13 O 41 ] 7− . [9] Heteropolyoxovanadates inhibit the corrosion of Al 2 Cu intermetallics due to the precipitation of a protective layer of vanadium phosphate.…”