If aluminium is corrosion resistant how come it reacts with hydrochloric acid?

Simply because it is not corrosion proof. Just about any common metal will react with hydrochloric acid. This is based on the electronegativity of the metal compared to the electronegativity of Hydrogen. Hydrogen ions will oxidize Aluminum, Zinc, Copper, Iron, Nickel and Chromium. Only "noble" metals like Gold, Platinum and Iridium are almost corrosion proof. Hydrochloric acid has no reaction on these metals, which only dissolve in a mixture of Hydrochloric and Nitric acids. Aluminum resists rusting because it forms a thin layer of oxide on the surface, coating the metal like a thin, transparent film of gl (Aluminum oxide is what rubies are made of. The color comes from Chromium). Both Aluminum and Chromium are very reactive with strong bases, however. This is why lye should never be used to clean chrome or aluminum.