Abstract: An aluminum foil to be etched for use as the electrolytic condenser electrodes is composed of a foil body of an aluminum purity of 99.9% or higher, and an oxide layer 20-70 .ANG. thick and formed due to contact of the foil body with an oxidizing atmosphere. At least one etching nuclei-forming element is concentrated in a boundary region and/or in an outermost surface region of the oxide layer, the boundary region being disposed between the foil body and the oxide layer, and both the regions having a thickness of 20 .ANG. or less. The ratio in ion intensity of a maximum concentration of the elements in these regions to a concentration of the elements in the inner layer of the foil body is 1.2-30. There are three patterns in distribution of the elements, so that the maximum concentration is in a predetermined ratio to the concentration in the surface region, the inner layer or a minimum concentration appearing between the regions.

Abstract: An aluminum alloy for heat exchangers, the alloy, comprising a base compostion selected from a group consisting of Al-Mg-Si composition containing 0.1 to 0.8 wt % of Mg, 0.2 to 1.0 wt % of Si and 0.3 to 1.5 wt % of Mn; pure-Al composition; Al-Mg composition containing 0.05 to 1.0 wt % of Mg; and a Al-Zn composition containing 0.05 to 2.0 wt % of Zn. The alloy further comprises 0.01 to 0.3 wt % of Fe and/or 0.01 to 0.3 wt % of Ni, wherein the balance are aluminum of purity of 99.9% or higher and unavoidable impurities contained therein, and content of Cu as one of the impurities is controlled to be 0.05 wt % or less.

Abstract: A heat exchanger comprises tubular elements and fin members. The tubular elements are made of an aluminum alloy containing 0.05 to 1.0 wt % of Mg, 0.2 to 1.2 wt % of Si, 0.2 to 1.5 wt % of Mn, 0.01 to 0.5 wt % of Fe, as necessary components, and further containing at least one of 0.05 to 0.3 wt % of Cr and 0.01 to 0.05 wt % of Ti, as optional auxiliary components, and 0.05 or less wt % of Cu as a controlled impurity, the balance being aluminum and unavoidable impurities. The fin members are made of another aluminum alloy containing 0.05 to 1.0 wt % of Mg, 0.2 to 1.2 wt % of Si, 0.2 to 1.5 wt % of Mn, 0.01 to 0.5 wt % of Fe, and further containing at least one of 0.01 to 0.1 wt % of In and 0.1 to 2.0 wt % of Zn as necessary components, and still further containing at least one or of 0.05 to 0.3 wt % of Cr and 0.01 to 0.05 wt % of Ti as optional auxiliary components, and 0.05 wt % or less of Cu as a controlled impurity, the balance being aluminum and unavoidable impurities.