Thanks, I'm pleased with the results. For starters, my tank was in o.k. condition... I've seen worse and I've seen better. There wasn't a lot of scaling; however, the metal was rusty and pretty much brown inside. In fact, it had several tanks of gas through it in recent years in that condition, but that's a good way to ruin carb needles among other things. I regret that I forgot to take a photo of the tank before I did the electrolysis.
First, I would recommend checking out the three links I pasted at the end of this post. They're all different and have something to offer. In fact, the moped one was a site that someone else posted to this site. Second, this process is not nearly as caustic as others and why I decided to use it, but understand the water/washing soda solution is an electrolyte. This process is slower, but from my understanding of how electrolysis works (ion exchange), I like its non-impact result on the good metal. Third, as do most, I learned a few things while studying up and while conducting the process. I'll provide some of my own learning lessons at the end:
The process
1. Close the lines, remove/drain fuel from tank, remove petcock.
2. Plug the tank where the petcock was (I used wine bottle cork).
3. Use a soap/water solution to clean out the tank (I used a few boxes of small nuts/bolts) and to removed scaling and other chunks and rinse.
4. Fill tank half full of fresh water, add the washing soda (1- tbsp per gallon), mix and fill the tank completely.
5. "Securely" fasten your sacrificial anode to the tank so it does not touch any part of the tank inside or out (I followed the recommendation of using a spray-paint cap).
6. Find a part of the tank where you can affix the negative charger lead and obtain a good connection (I used the frame mount). I've read where folks have used the petcock tank threads but I didn't want to mess up the threads (you don't want to do this process with the petcock on the bike (for multiple reasons).
7. Start zapping. I used a 12v, 6A charger, hooking up the negative lead to the tank mount and the positive lead to the sacrificial anode. The anode was a non-coated, 1/4 steel rod.
8. I zapped mine for a total of about 3-days (I dumped out the tank and cleaned and brushed the sacrificial anode three times throughout the process. It gets full of junk and it's good to see how much progress is being made.
9. I used a pressure washer and the nuts/bolts to remove as much of the black residue (a carbon like film after it is done that results from the ionization).
10. After making sure it was thoroughly rinsed, sprayed about 1/3 bottle of STP to immediately protect the bare metal and eventually filled it up with gas and a bit of pre-mix.
Lessons learned:
1. The sacrificial anode will get sucked against the tank by the electrical current if not secured. I used the spray-paint cant cover, EZ-clamps, and tape to secure mine.
2. I'm away from my permanent residence and do not even have a garage right now so... these projects are much more difficult than usual for me.
3. I had my charger sitting close to the tank and when I overfilled it with water the first time around, I gave my charger a shower. Luckily, after taking it apart and cleaning it and the fact that if was off at the time shower, it still works.
4. I've seen conflicting information as to whether you can use baking soda vs. washing soda. I used washing soda to be safe but they are supposedly close to the same thing.
5. I should have prepped my tank better to protect the paint. I haven't noticed any problems yet but I got a lot of STP on my tank paint when I was spraying the inside. Probably a good idea to cover it somehow.
I'm certainly open to your questions/comments but I'm no expert; however, between the below links, and possibly some to my lessons learned, you'll see great results for yourself. Cheers! Orion
http://www.rickswoodshopcreations.com/Miscellaneous/Rust_Removal.htmhttp://www.mopedarmy.com/wiki/Removing_rust_from_a_gas_tankhttp://www.kawasakimotorcycle.org/forum/projects-how-write-ups/49040-help-rusted-gas-tank.html