Abstract: Metal surfaces, particularly the zinciferous surfaces of zinc-coated steel, can be given a chromate conversion coating that is superior in terms of blackening resistance and white rust resistance by drying into place on the surfaces a layer of a treatment liquid that contains water, hexavalent chromium atoms, trivalent chromium cations, nitrate ions and one or more types of metal ions selected from the group consisting of Ni, Co, Zn and Al, the molar ratio of the total of these metal ions to nitrate ions being in the range from 0.05 to 1.0, the molar ratio of trivalent chromium ions to hexavalent chromium atoms being in the range of 0.11:1.0 to 1.0:1.0, and the molar ratio of nitrate ions to total chromium atoms being in the range of 2.1 to 5.5. Preferably, the coating formed has a chromium content of 10 to 100 mg/m2.

Abstract: The invention is a method for the accurate control of the conversion film thickness produced on aluminiferous metal materials by fluorine-containing acidic conversion treatment baths; and a simple method for determining the EFC value (Effective Fluorine Concentration). The EFC value is determined by potentiometric titration of a fluorine-containing acidic conversion treatment bath having pH<4 without prior pH adjustment using a fluorine ion electrode as indicator electrode. The titrant is an aqueous solution containing the Al ion, La ion, Y ion, Zr ion, Ga ion, Ce ion, or Be ion, an inflection point in the potential curve is used as an indication of the activity of the conversion treatment bath.

Abstract: A microwave energy source is associated with a heating medium containing a microwave energy absorption material so that the heating medium is heated to a high temperature when it is irradiated with microwave energy and produces infrared heat energy. The heating medium can be incorporated in a cooking dish or on the interior of a heat insulating housing.