Improvement of the corrosion behavior of aluminum alloy 6061-T6 with yttrium and lanthanum conversion coatings

Abstract

In this study, yttrium-and lanthanum-based conversion coatings were deposited on a 6061-T6 aluminum alloy with cathodic electrochemical deposition using Y-and La-nitrate precursors. The optimum] ratio was evaluated with cyclic-voltammetry (CV) curves. The influence of the conversion-treatment time was studied by performing the experiment for periods of 10 and 20 minutes. Optical microscopy was used to determine the coating morphology and the anticorrosive properties were studied using linear polarization (LP) and electrochemical impedance spectroscopy (EIS) in a 5-g/L NaCl solution. The electrochemical results revealed an obvious improvement in the corrosion resistance against the aggressive media after an extended imersion test for 48 h, indicating a good efficiency of the Y-and La-conversion coating. Keywords: aluminum alloy, 6061-T6, conversion coating, rare earth elements, lanthanum, yttrium V pri~ujo~em~lanku avtorji opisujejo nanos konverzijske (pretvorbene) prevleke na osnovi itrija in lantana na Al zlitino 6061-T6 s katodno elektrokemijsko depozicijo (nanosom) z uporabo Y in La-nitratnih prekurzorjev (izhodnih surovin). S cikli~nimi voltametri~nimi (CV; angl.: Cyclic Voltammetry) krivuljami so ovrednotili optimalno razmerje[tudirali so vplive~asa na pretvorbo z izvedbo 10 in 20 minutnih preizkusov. S pomo~jo svetlobnega mikroskopa so podali morfologijo prevleke. S pomo~jo linearne polarizacije (LP) in elektrokemi~ne impedan~ne spektroskopije (EIS) v 5 g/L NaCl pa so {tudirali korozijsko odpornost prevleke. Rezultati elektrokemijskih preiskav so pokazali jasno izbolj{anje protikorozijske za{~ite v agresivnem mediju po podalj{anem 48 urnem potopnem preizkusu. To ka`e na dobro u~inkovitost izbrane obdelave za izdelavo Y in La pretvorbenih prevlek. Klju~ne besede: zlitina na osnovi aluminija, 6061-T6, pretvorbena prevleka, redki elementi zemlje, lantan, itrij

Effect of dispersed oxide of cerium, lanthanum and thorium on the corrosion behaviour of tungsten in 3.5 wt-% NaCl solution

“…Anti-corrosive coatings have also been produced with rare-earth elements to protect metals or alloys. Lanthanum, for example, has been used to improve the corrosion resistance of aluminium alloy 6061-T6 [11]. Magnesium alloy AZ91D has increased its corrosion resistance using a cerium coating [12].…”