(1) In terms of content, aluminum is much larger than gold, and in terms of value, gold is a precious metal; The price of aluminum has decreased because the smelting technology of aluminum has been continuously improved and the cost has been reduced;

(2) Alumina reacts with hydrochloric acid to produce aluminum chloride and water. According to the law of conservation of mass, its chemical equation is: Al2O3+6HCL = 2AlCl3+3H2O; Rust is characterized by being very loose. The way to prevent iron from rusting is to isolate iron from oxygen and water, keep iron products dry, or coat the surface of iron products with oil or paint.

So the answer is: (1) Gold is a precious metal; The smelting technology of aluminum has been continuously improved and the cost has been reduced; (2)al2o 3+6h cl = 2 ALC L3+3H2O； Loose; Keep iron products dry.