Chlorine-containing gases including HCl or Cl2 severely attack many metals. Table 16 shows the applicable temperatures for various materials in dry HCl and Cl2 gases.7,8,10,30,31 Nickel can be used in hydrofluoric acid provided there is no condition of flowing in which its protective fluoride film would be removed. Nickel also can be used at temperatures higher than 500 °C, similar to Alloy 600. Nickel — chromium-iron is better as a structural alloy in this application due to its high strength compared to pure nickel. However, nickel and Alloy 600 severely cor­rode in HCl and Cl2 gas in the presence of water vapor. Aeration or the presence of oxidizing chemi­cals will also increase corrosion rate of nickel in hydrofluoric acid.