SOHC.co.uk Forums > CB350/400
Why can't you have rusty petrol tank shot or bead blasted ?
SteveW:
Be careful though, the bubbles produced are hydrogen.
I did mine outside over a couple of days.
AshimotoK0:
I haven't tried the electrolysis method personally but heard very good reports about it. One thing I considered was covering the electrode with the plastic netting they use to protect new machine tools. That way you could push the electrode deep down in the sides of the tank and not have the danger of the electrode touching the metal of the tank.
the-chauffeur:
--- Quote ---Why can't you have rusty petrol tank shot or bead blasted?
--- End quote ---
You can - nothing stopping you. If you mean why isn't it a good idea that's different - and I can tell you that having had the outside of a tank sandblasted, I'd be very wary of trying to do the insides the same way.
Long story, but I'd decided to get a tank powdercoated (yeah, long story . . . don't ask) and since the frame was going the same way, I just added the tank to the set of bits to get blasted. Saw it halfway through the process and it looked absolutely fine; paint free and no rust either inside or outside. Powdercoating completed and it looked great. Things started to go sideways when I put fuel in it . . .
. . . the grit was sharp enough to put two near microscopic holes in the underside. Poking around confirmed there was no rot; the grit had simply found a couple of very slightly weak spots around weld seams and blown though. Fuel and powdercoat really don't mix, and so I ended up needing to get the tank done again. And then the rebuilt fuel tap leaked . . .
Suffice it to say that unless you're going to use a very soft media type or do something like vapour blasting, it's really not worth risking the cost of a paintjob simply to save a couple of hours work. At the same time, the insides of tanks can incorporate some very odd shapes that aren't easy to blindly work around. The tank I had done is from the mid-60's and has such a high middle section where it straddles the frame that it needs a connector hose to get fuel from one side to the other (hence the number of weld seams). Working around that sort of thing would be a nightmare - and as others have pointed out, getting the media and the ultrafine dust it generates out when you're done would be more trouble than it's worth.
You really don't want any of that getting into the engine . . .
McCabe-Thiele (Ted):
--- Quote from: the-chauffeur on September 06, 2020, 12:25:52 AM ---
--- Quote ---Why can't you have rusty petrol tank shot or bead blasted?
--- End quote ---
You can - nothing stopping you. If you mean why isn't it a good idea that's different - and I can tell you that having had the outside of a tank sandblasted, I'd be very wary of trying to do the insides the same way.
Long story, but I'd decided to get a tank powdercoated (yeah, long story . . . don't ask) and since the frame was going the same way, I just added the tank to the set of bits to get blasted. Saw it halfway through the process and it looked absolutely fine; paint free and no rust either inside or outside. Powdercoating completed and it looked great. Things started to go sideways when I put fuel in it . . .
. . . the grit was sharp enough to put two near microscopic holes in the underside. Poking around confirmed there was no rot; the grit had simply found a couple of very slightly weak spots around weld seams and blown though. Fuel and powdercoat really don't mix, and so I ended up needing to get the tank done again. And then the rebuilt fuel tap leaked . . .
Suffice it to say that unless you're going to use a very soft media type or do something like vapour blasting, it's really not worth risking the cost of a paintjob simply to save a couple of hours work. At the same time, the insides of tanks can incorporate some very odd shapes that aren't easy to blindly work around. The tank I had done is from the mid-60's and has such a high middle section where it straddles the frame that it needs a connector hose to get fuel from one side to the other (hence the number of weld seams). Working around that sort of thing would be a nightmare - and as others have pointed out, getting the media and the ultrafine dust it generates out when you're done would be more trouble than it's worth.
You really don't want any of that getting into the engine . . .
--- End quote ---
Thanks for the explanation and evidence of your experience - i'm definitely not going to go down the blasting route!
Over the next few days when I have finished swishing my gravel about I plan to put some white vinegar I already have in stock to use before I proceed to electrolysis. I plan to use a multi phased approach as necessary to get a good finish.
Reading online reviews on Evaporust they talk about it leaving metal surfaces a dark /blackish colour. I am very aware that surface rust soon returns so the idea of some sort of residual protective coating appeals. Its a shame that a reverse electrolysis cant easily be used at home to coat the tank surface with zinc or nickle.
mike the bike:
It's a pity you can't use the same technique for copper plating the inside of the tank. There was some sound technical reason why not but I can't remember what it was.
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