Abstract: The invention relates to a method of manufacturing an outside decorative trim strip of a motor vehicle, such as window surrounds or body shell trim, made of aluminum alloy, by shaping and brightening of a plate or strip made by vertical continuous casting of an alloy slab of series AA5xxx of high purity, homogenization-heating of the slab, hot rolling, cooling, cold rolling with intermediate annealing in a continuous tunnel furnace, or holding between the solvus temperature and the alloy burning temperature typically for 3 seconds to 5 minutes, quenching in air or water, possible annealing at a temperature of 100 to 200° C. The invention also relates to a decorative trim strip of motor vehicle manufactured using such a method.