A method of diffusion coating a surface of an alloy product containing at least 5 wt.% iron with a chromium-silicon coating uses a dual activator containing a fluoride salt and a chloride salt, at least one of those salts particularly being ammonium chloride or another ammonium halide salt. Upon heating the ammonium salt will form a reducing environment containing molecular hydrogen. The presence of molecular hydrogen speeds up the chemical reactions by an additional reduction reaction that creates the surface coating which enables the coating reactions to occur at lower temperatures and shorter hold times. Alternatively, one can use non-ammonium type fluoride salts and chloride salts in combination with another source of molecular hydrogen. This source could be hydrogen gas injected into the system.
