SOTP Vintage Series
Main Motorcycle: The one between my legs
Join Date: Feb 2009
Location: Upstate NY
Other Motorcycle: A few
Extra Motorcycle: Yes
I'll be needing some cheese and crackers with this whine
Well, it's been two weeks since I filled my S90 tank up with vinegar to remove what little (I thought) rust there was inside. I dumped the vinegar today and was not overly impressed. All the rust spots had turned a blue black color. I went in to a spot I could reach with a dental pic and scratched off the black crud. It revealed pits in the metal that were still black on the bottom of the pits. I thru in a handful of sheet rock nails and did the cha-cha again. I cleaned off all the rust spots and left behine dark pits.
So I threw in the towel and grabbed the phos acid (metal prep) I test an area on the underside of the tank to see if it would hurt the paint and no problem. So I filled the tank about 1/3 full, sloshed it around and let it sit for several hours, sloshing occasionally and propping in different positions to let the acid work on various areas of the tank, even upside down to get the top. Phos acid did a much better job, plus it leaves behind a zinc coating that prevents flash rust from forming.
Now for the whine. What I thought was a very nice original paint tank, turned out to have 5 pin holes along the bottom weld seam, which forms a very nice crevice for moisture or whatever to collect and work on the metal. Since this is not a Triumph tank, I leave it there.
The vinegar did remove rust. And given the low temps in my shop this time of year, it might have done a better job had the temps been higher. Rule of thumb is a chemical reaction doubles in speed for every 10 deg you raise the temp. That's why washing your hands in hot water does a better job.
So, if you are not in a rush and can let the tank sit for a month or two full of vinegar, and you put it in your house or a warmer area than outdoors in the fall/winter months, it might just do the job. But, you have to protect the surface from flash rust when you pour it out. So, for me, phosphoric acid is the best way to go because it cleans out the rust faster and prevents future rusting.