The localised corrosion associated with individual second phase particles in AA7075‐T6: A study by SEM, EDX, AES, SKPFM and FIB‐SEM

Abstract

To investigate the role of intermetallic particles in the localised corrosion of AA7075‐T6, three particles were monitored over 16 h immersion in 3.5 wt% KCl solution. These were examined using Auger electron spectroscopy, energy dispersive X‐ray spectroscopy, scanning Kelvin probe force microscopy and focused ion beam‐scanning electron microscopy. Despite similar Volta potential measurements, the corrosion microchemistry varied significantly with composition. A Al7Cu2Fe intermetallic resulted in trenching while a (Al,Cu)6(Fe,Cu) intermetallic showed crevice corrosion and sub‐surface intergranular corrosion and a Al12Fe3Si intermetallic appeared to be galvanically inactive but showed crevice formation at the matrix interface and sub‐surface intergranular corrosion.

Inhibitory effect of cysteine and lanthanides on AA7075‐T6 in neutral NaCl solution

“…[20][21][22][23][24] The most common cathodic IMPs are Al 7 Cu 2 Fe, (Al, Cu) 6 (Fe, Cu), and Al 3 Fe, while Mg 2 Si is the most common anodic IMP. [25][26][27][28][29] IMPs containing Mg, Zn, and Si are anodic to the aluminum matrix. They dissolve in the initial period of the corrosion process (Figure 2, Spectrum 3) and do not significantly deteriorate the corrosion properties of the tested aluminum alloy.…”

Cerium citrate as ecologically friendly corrosion inhibitor for AA7075 alloy

“…IMCs rich in copper and iron, such as Al 7 Cu 2 Fe, (Al, Cu) 6 (Fe, Cu) and Al 3 Fe have a cathodic character, and IMCs rich in magnesium, such as Mg 2 Si are anodic in relation to the aluminium matrix. [7][8][9][10][11] Cathodic IMCs in AA7075 alloy are the places where the cathodic reaction of oxygen reduction takes place in neutral chloride solutions. Cathodic IMCs are especially harmful because pits form along the perimeter of these IMCs.…”

Effect of preaging temperature on microstructure evolution, mechanical and corrosion behavior of RRA‐treated high‐zinc 7068 alloy

“…Birbilis and Cavanaugh [23,24] investigated the microgalvanic effects of anodic β (MgZn 2 ) and S (Al 2 MgCu) phases and found that increase in their volume fraction can increase the number of microgalvanic couples which is detrimental from the corrosion perspective. [25,26] Heat treatments such as RRA are used to control these microstructural features. Thus, for a specific 7xxx series alloy it is important to optimize the RRA treatment parameters that control all the corrosion-sensitive features like the morphology, distribution, volume fraction, and chemical composition of the second phase precipitates along with the width of PFZ.…”