Getting rid of rust stain

[Boatwayupnorth]

Owning a steelboat means fixing rust. That's just the way of things. This time on the targa. Sun was shining and promised to keep doing so for some days (which is rare, here way up north). In my neverending wisdom I got to it, angle grinder, flapdisc, epoxy primer and two-part urethan. Done it before and will do again. A light breeze blew, halv the dust up my nose and the other halv over my deck (once white). Two days later rust blooms appeared and I can't get it of them.
See pictures. Have tried vinegar without success. A compassionate neighbor suggested Coca Cola. Will try that tomorrow.
Has anybody had the same problem? And solved it? Anybody? PLEASE!