a multiplex protective mcraly - based coating system for an m - based superalloy base material , where m is at least one of iron , cobalt and nickel , has a surface layer containing aluminides of platinum and the m constituent of the coating . there may be a single surface layer containing platinum modified aluminide , or alternatively a double surface layer in the form of a top layer containing platinum modified aluminide and a sub - surface layer containing aluminides substantially without platinum modification . the surface layer may also have extra chromium in solid solution in the m constituent of the coating , the chromium content in the surface layer of the coating being not more than about 40 wt . %, preferably 35 to 40 wt . %. the process for production of such a system involves deposition of an mcraly coating , optionally chrimizing it , and then aluminising and platinising it using appropriate amounts of platinum and appropriate heat treatments to obtain the desired variant of the coating system . alternatively , to boost aluminium levels near the surface , the coating can be platinised immediately before it is aluminised .