If the intercooler is alloy then i would guess that the VHT will not take to it as the cooler will not get hot enough for the VHT to work as it should.
It may also start flake off as it is for exhaust, so what you need to do is rub a scotch bright over it to give it a "key" and then put 2 light coats of this
http://www.halfords.com/webapp/wcs/..._productId_170745_langId_-1_categoryId_165625
Then just wait for it to "tack" off for about 5 or so mins then you can paint over it with the colour of your choice this is called "wet on wet" if you was to leave the primer to dry you would then need to give it a "key" again this way you only need to do it once.
My brother in law has done his Escort turbo rad and cooler in this way with no problems and we have both worked on Aston Martins for well over 12 years and this is the way we prep anything alloy.
Hope this helps anymore info then please pm me.