Tank Cleaning Process
I just cleaned a T140V tank that I got on ebay a couple of months ago.. I've done others before and have tried some of the "green" approaches like washing soda/electrolysis. Forget that process. Here's what I believe to be a provent method.
First, drain the tank and get it dry inside. An air hose will quickly dry any gasoline that is in there. Keep in mind there are still vapors present so no open flames or sparks for now.
Go to the hardware store and in the plumbing dept you can find a rubber stopper used to plug unthreaded pipe. Get the size that fits snug in your tank neck. It will have a bolt running thru it that squeezes the rubber to make it expand and seal. While you are there, you might want to get a big wingnut to replace the hex nut on the stopper, making life a little easier. Also pick up a couple of 1/4" NPT pipe plugs.
Put teflon tape on the pipe plugs and screw them into your petcock bungs. Not to tight because the plugs are tapered and the bungs are straight thread. Just snug them up. The telfon tape will seal things.
As previously mentioned in another post, put a handful of sheet rock screws in the tank. A full handful. I like standard size 1-1/4 inch screws because they can get into all the nooks and crannies. Now shake the daylights out of the tank like a big gourd player in a Latino Band. Develop a method so you make sure all the internal surfaces will get addressed. Don't forget to turn the tank upside down and do the top surfaces. After your arms hurt from shaking the tank, dump the screws into an old t-shirt or similar. All the dry rust and crud will come out with the screws. Separate the screws, clean them in the rag, put them back in and go at it again. When you have most of the dry rust cleaned out, it's not time to clean the tank. I like Mineral Spirits. Won't hurt your paint. Acetone WILL hurt your paint. Fill tank with about a quart of min spirits, put the screws back in and go at it again. I like to use a swirling motion because it cetrifuges the screws to the outside of the tank and all those little sharp threads scour the tank walls. Do this for sometime, like until your arms start getting tired. Then put a t-shirt or other rag into a funnel and dump the min spirits into a jug. If you have paper coffee filters, you can filter the min spirits even better than the t-shirt. It will be red with rust. Keep in mind that the coffee the filters will drain slower. I've had to squeeze them to get the last portion of liquid thru them. Dump the filtered min spirits back in along with the screws and have at it again. Do this until it look pretty good inside.
For inspection, you can get a small inspection mirror from Harbor Freight for a couple of bucks. Then get yourself an old Christmas light socket, the size used in window candles and nightlights. Put a 40W candelabra bulb in it (more light, and dangle the light inside the tank and inspect the corners and upper areas with the mirror. If you still see rust or pits with rust in them, give it another go with the min spirits and screws. When you are sure you've done as good a job as possible, dump the old min spirits and put in a quart of fresh min spirits and flush out the tank one more time. Inspect it again.
Now you can take out the 1/4 NPT plugs, leave the neck open and blow some air thru the tank to dry the min spirits. When it is bone dry inside, go back with your mirror and tank inspection light and give another looking over. If it was just minor rust in your tank, you may not need to seal it. But you are not done yet. It will start to rust again as soon as it is dry.
Now go to your local auto body supply shop and get a gallon of Metal Prep. It is phosphoric acid. Put your plugs back in and dump in a pint of metal prep. Put the rubber bung in the neck and slosh the acid around. Wear goggles, rubber gloves and protective clothes. This is not really dangerous stuff, but can hurt your eyes and irritate your mucous membranes. You also want plenty of air circulation so do this outside. I wear a painting mask when I do it. Keep circulating the acid in the tank. I would say you need to do this for 5 to 10 minutes. When you pour it out, be very careful it does not run down the tank and hurt your paint. Have a wet rag available to mop up any spillage. Now, go back in and take a look with your light. Tank should look very clean inside. If you still see dark spots, go at it with the acid again. Once it looks good inside, and it should be a nice dull gray, let it air dry. It may take awhile. You can put an air hose inside to hurry the process. The metal prep leaves behine what I believe is a thin zinc or phosphoric coating the prevents further rusting. Once it is dry, I like to dump in a quart of denatured alcohol and flush out the tank a couple of times to make sure all the acid is neutralized and any loose stuff left behind gets flushed out. The alcohol dries very quickly once you dump it out.
You will need to do an acid cleaning with the Caswell system. So you might want to call them and ask what they use and tell them you'd like to try the process above first because your tank may not need lining. When you do the process above, you may be halfway thru the Caswell prep process. That's why I say to call them. I've spoken to them and they are very helpful. I have not used their sealant, but researched all the different ones should I have needed on on the T140 tank. When I spoke to them they also confirmed that they have tested their sealer with alcohol based fuels and have not had a problem. It is phenolic based sealant. Empire GP, which paints a lot of racebikes, many of which run on alcohol, uses this sealant exclusively.
I've attached some before and after pictures here of the T140 tank I just cleaned using this method. In one of the after shots the tank is not fully dry yet and that's why it is shiny inside.
Hope this helps.
regards,
Rob
