NOVELTY - An apparatus for producing hydrogen gas by mechanical scraping of a surface of an aluminum-containing material, in the presence of an aqueous medium, comprises reaction chamber having discharge port, adapted to sealably contain aqueous medium; an aluminum-containing workpiece (10) having working surface (12); a scraping mechanism (20) having scraping element (22) adapted to contact working surface, and aqueous medium, where the aluminum-containing workpiece, scraping element, and aqueous medium are disposed within the chamber.    USE - As an apparatus for producing hydrogen gas (claimed), used in fuel cell, computing device, toy, cellular phone or other portable electronic equipment.    ADVANTAGE - The apparatus converts a large fraction of the aluminum to reacted aluminum in a controlled, safe manner, thus maximizing the hydrogen output potential of the aluminum. The efficiency of aluminum conversion to reacted product is very important. Unreacted aluminum is less than 50, preferably less than 40, especially less than 30) wt.%. In some cases, greater than 90% or greater than 95% of the original aluminum is reacted (corresponding to less than 10% or less than 5% unreacted aluminum), releasing near the maximum amount of hydrogen possible. The mechanical energy is applied almost totally to the surface of the aluminum, thus requiring less energy than alternative mechanical approaches in which mechanical energy is less well utilized. The oxidized aluminum is relatively easily scraped off so there is little or no attrition to the scraper. The scraper is made of a hard material, so its attenuation (wear) is minimized. The hydrogen production system is highly energy efficient to be economical, requiring a low energy input per energy value (hydrogen gas) produced. Energy losses includes heat losses, mechanical losses including drag forces in aqueous medium, and energy spent in exposing fresh aluminum surface and producing aluminum particles. The apparatus produces hydrogen gas by mechanical scraping of an aluminum surface, other reactive metals such as magnesium, magnesium alloy, or magnesium-containing materials may also be scraped and reacted with water or an aqueous solution to produce the hydrogen gas.    DETAILED DESCRIPTION - An apparatus for producing hydrogen gas by mechanical scraping of a surface of an aluminum-containing material, in the presence of an aqueous medium, comprises reaction chamber having a discharge port, and is adapted to sealably contain the aqueous medium; an aluminum-containing workpiece (10) having a working surface (12); a scraping mechanism (20) having at least one scraping element (22) adapted to contact the working surface, and an aqueous medium; the aluminum-containing workpiece, the scraping element, and the aqueous medium disposed within the chamber. The chamber is adapted to be sealed with respect to an external environment. The chamber is further adapted, for discharging the hydrogen gas evolved through the discharge port, during contacting of the aqueous medium and the particles within the chamber. The surface and the scraping element are adapted to move in a relative motion. The chamber includes a flexible external wall, adapted to be flexed by a force external to the chamber, to achieve the relative motion, where, in a relaxed condition of the external wall, the scraping element is stationary with respect to the working surface, and where, in an operating condition, the scraping element scrapes against the working surface to effect a liberation of aluminum-containing particles from aluminum-containing workpiece.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic, partly cross-sectional view of a portion of sub-arrangement of hydrogen generating system.    Aluminum-containing workpiece (10)    Working surface (12)    Scraping mechanism (20)    Scraping element (22)    Spring assembly (26)    Dive arrangement (50)