A Group IIIA element fluoride-containing coating comprising a Group IIIA element fluoride phase which contains at least 50% of a crystalline phase of the orthorhombic system belonging to space group Pnma is formed on a member for imparting corrosion resistance so that the member may be used in a corrosive halogen species-containing atmosphere. When the state of a crystalline phase is properly controlled, the coating experiences only a little color change by corrosion. A Group IIIA element fluoride-containing coating having a micro-Vickers hardness Hv of at least 100 is minimized in weight loss by-corrosion.