Electrochemical corrosion of Al-Pd alloys in HCl and NaOH solutions

Abstract

The corrosion performance of as-solidified Al-Pd alloys in HCl and NaOH aqueous solutions is investigated in this work. Four different alloys (Al 88 Pd 12 , Al 77 Pd 23 , Al 72 Pd 28 and Al 67 Pd 33 , element concentrations are given in at.%) were prepared from high purity Al and Pd lumps by arc-melting in Ar. Subsequently, the alloy microstructure and phase occurrence were investigated by a combination of scanning electron microscopy and room-temperature powder X-ray diffraction. The assolidified Al-Pd alloys were found to consist of several single-phase microstructure constituents with various structures and chemical compositions, including structurally complex intermetallic phases. The polished surfaces of the Al-Pd alloys were subjected to electrochemical polarization in aqueous HCl and NaOH solutions (0.01 mol.dm-3) at 21±2°C. The corrosion experiments were conducted in a standard 3-electrode cell controlled by potentiostat. The corrosion potentials and corrosion current densities were determined by Tafel extrapolation of the experimental polarization curves. Phase dissolution has been observed on the alloy surfaces and some of the phases were preferentially corroded. The effects of the alloy microstructure and the phase occurrence are evaluated. The local nobility of individual intermetallic compounds is discussed. Finally, the conclusions for the alloys corrosion performance in acidic and basic solutions are provided.

Influence of Sealing Treatment on the Corrosion Resistance of PEO Coated Al-Zn-Mg-Cu Alloy in Various Environments

“…In addition, due to changes in pH and Cl − ion concentration in the corrosion solution [3,4], the i corr of the siloxane sealing PEO coating increased, and the E corr and R p decreased, as the concentration of the solution increased. The reason for this change is that the corrosion solution passed through the micro defects of the siloxane layer, causing the layer to crack.…”

“…Aluminum alloys are widely used in many engineering applications due to their superior performance. But in corrosive environments such as humid, acidic, and alkaline environments, aluminum alloys are prone to corrosion [1][2][3][4]. To protect or mitigate corrosion processes, protective coatings are typically applied to metal surfaces.…”

Chlorine corrosion of blast furnace gas pipelines: Analysis from thermal perspective

“…Each layer is considered as a uniform material with the thermal conductivities of λ 1 , λ 2 and λ 3 , respectively. Then, the total thermal resistance of the three-layer cylindrical walls is (12) (5) Heat transfer of the BFG pipelines (a) for single-phase heat transfer section The convective heat transfer from the BFG to the inner wall of the pipelines is (13) where l 1 is the length of the single-phase section [m], T and t 1 are the mean temperature of BFG and the inner wall of the single-phase section [K], respectively.…”

“…The conductive heat transfer through the threelayer cylindrical walls is (14) The convective heat transfer from the outer of the pipelines to the surroundings is (15) For simplicity, the whole heat transfer process is considered as a steady-state process, then (16) From Eqs. (13) to (16), the heat transfer is written as (17) (b) for condensation heat transfer section The convective heat transfer from the BFG to the inner wall of the pipeline is (18) where l 1 is the length of the condensation section [m], and the superscript ′ represents the parameter at the condensation heat transfer section. The conductive heat transfer through the threelayer cylindrical walls is (19) The convective heat transfer from the outer of the pipelines to the surroundings is (20) Also, (21) From Eqs.…”

“…According to [12,13], the corrosion of BFG pipelines is mainly caused by chlorine. Three kinds of chloride exist in the BFG, including HCl, NH 4 Cl and NaCl (or KCl, ZnCl, etc.)…”