There's a prudent hierarchy of acids for rust stain removal. The least aggressive is oxalic, then phosphoric, and then hydrochloric. The safe approach is to use no ore strength than you need - the stronger the acid the greater its ability to corrode metals.
There are a number of oxalic acid based spray type rust stain removers, such as the Starbrite product. There are also phosphoric acid spray treatments - often called a rust converter - and Naval Jelly is phosphoric acid based. Common muriatic acid is hydrochloric and should be diluted to 10% strength if bought straight at a hardware or pool supply company. Sno Bowl is hydrochloric acid based.