hi pitrack 1
there are a couple of different types of rust converters
one which after application turns the rust black and after its dried should be wiped down with a damp cloth and can be top coated as is , but I would recommend first a under coat in rich zinc paint which is available in a spray can.
other type is phosphoric acid
after applying when dry rub down with a damp cloth, this type of converter some times dries with some white powder on the surface , rub all powder off before painting.
again i a would recommend using a rich zinc under coat before finishing with a top coat.
both types of rust converter can be top coated over after they have dried but the use of the rich zinc is extra insurance against the rust returning and bleeding through the paint
would not recommend using rust converter in a fuel tank, if its a common tank best to get another clean tank
if you really need to use the tank you can buy from auto shops a fuel tank cleaner repairer.
I have used this product myself ,they sell tank repair kits for cars and motor bikes
motor bike kit will repair two or three mower tanks
first it removes , converts rust , then tank is relined with a rock hard ceramic coating, will fill rust pin holes leaks ect no more rust problems, but its not cheap at around $80 for a motor bike fuel tank repair kit .
hope that helps damo
