Corrosion resistance and passivation behavior of 3004 AlMnMg and 4044AlSi aluminum alloys in acid-chloride electrolytes
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IOP publishing
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Corrosion resistance of 3004 and 4044 aluminium alloys (3004Al and 4044Al) in neutral chloride
(0.5%–4.5% concentration), sulphate (0.00625M-0.1Mconcentration), and chloride-sulphate
(0.00625MH2SO4/0.5%–4.5% chloride concentration) solutions was studied with potentiodynamic
polarization, open circuit potential, cyclic polarization, and optical microscopy. Results show 4044Al
exhibited higher resistance to general corrosion while 3004Al was more resistant to localized
corrosion. Corrosion of 4044Al decreases with increase in chloride concentration while 3004 Al
increases. Corrosion rate values for 3004Al and 4044Al in sulphate solution were generally similar
between 0.061–0.395mmy−1 and 0.168–0.213mmy−1, respectively. In chloride-sulphate solution,
corrosion rate of 3004Al increased from 0.130mmy−1 to 1.563mmy−1 at peak chloride concentration
whereas the corrosion rate of 4044Al is near constant. The passive film on 4044Al is found to
weaken significantly with increase in chloride concentration. Passivation values varied from 0.39 Vat
0.5% chloride concentration to 0.01 Vat 4.5% concentration while the potential at which stable
pitting occurred increased. The passivation range values for 3004Al are relatively stable with respect to
chloride concentration. Results from cyclic polarization experiments show the deterioration rate of
both alloys in NaCl solution is subject to chloride concentration. The results show the alloys corrode at
all NaCl concentrations (0.5%–4.5%) with the lowest pitting corrosion risk in 0.5% and 1.5%NaCl
solutions. The highest pitting corrosion risk of the alloys occurred in 3.5% NaCl solution. Significant
localized morphological deterioration is visible throughout the entirety of 4044Al relative to the
adjacent Al alloy matrix compared to total surface deterioration on 3004Al.
Keywords
TJ Mechanical engineering and machinery, TP Chemical technology