Commercial mild steel was used as a standard material in this study. The high temperature corrosive environments were wet air, water steam and water steam with hydrogen chloride of 0.5 and 10 vol.% as average volume percentages during tests. The two corrosive gases were supplied from the flask as boiling 10 and 20 wt.% hydrochloric acid solutions respectively. The tested temperatures were 673, 773 and 873 K in the corrosion/oxidation tests and 873 K only in the single particle impact tests.