The disclosure relates to a method of coating a high-strength aluminium object with polymer and surface-treating it, for improved corrosion resistance. A polymer composition is coated onto the surface (c) of the aluminium object and is sintered or melted fast, at the same time as solution treatment (f) for precipitation hardening takes place. The polymer composition substantially comprises a fluorine-containing polymer, preferably PTFE. According to one preferred embodiment of the method according to the present invention, the polymer coating is sintered or melted fast on the aluminium surface during approx. 15 minutes at approx. 420 DEG C. After solution treatment and simultaneous surface treatment at elevated temperature, the aluminium object is rapidly cooled to room temperature (g) and precipitation hardened thereafter by means of artificial ageing (j) preferably at approx. 120-150 DEG C during approx. 24 hours.