Author Topic: Why can't you have rusty petrol tank shot or bead blasted ?  (Read 749 times)

Offline Macabethiele

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Why can't you have rusty petrol tank shot or bead blasted ?
« on: September 03, 2020, 06:03:11 PM »
I guess it might be either an access issue or removing the waste but why not the above - I'm tiring of swishing my tank with gravel in it  every time I go in my garage.
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Offline SteveW

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Re: Why can't you have rusty petrol tank shot or bead blasted ?
« Reply #1 on: September 03, 2020, 06:54:22 PM »
I have cleaned the tank on my RD350 with amazing results.

Wash the tank out with water then get a small tub of Bicarbonate of soda from the supermarket. Mix it with water then fill the tank to the brim, I use half the tub with full tank of water.

Connect a DC power supply, battery charger or whatever. Negative to the tank, and the Positive to a steel bar (I used an old Allen key) and put it in the filler neck but don't let it touch the tank.

Turn power on and watch it fizz, keep topping the water up and every now and then clean the steel bar. It will take a good few hours. Also swirl the tank around to removed any trapped pockets of air.

Best to do it outside as the bubbles produced are Hydrogen  ;)

I don't have a before pic but it was so bad I was on the lookout for a new tank.

This is a fairly slow process, it probably took 12 hours or so.
« Last Edit: September 03, 2020, 06:58:09 PM by SteveW »
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Offline Macabethiele

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Re: Why can't you have rusty petrol tank shot or bead blasted ?
« Reply #2 on: September 04, 2020, 12:20:19 AM »
I have cleaned the tank on my RD350 with amazing results.

Wash the tank out with water then get a small tub of Bicarbonate of soda from the supermarket. Mix it with water then fill the tank to the brim, I use half the tub with full tank of water.

Connect a DC power supply, battery charger or whatever. Negative to the tank, and the Positive to a steel bar (I used an old Allen key) and put it in the filler neck but don't let it touch the tank.

Turn power on and watch it fizz, keep topping the water up and every now and then clean the steel bar. It will take a good few hours. Also swirl the tank around to removed any trapped pockets of air.

Best to do it outside as the bubbles produced are Hydrogen  ;)

I don't have a before pic but it was so bad I was on the lookout for a new tank.

This is a fairly slow process, it probably took 12 hours or so.

That sounds interesting I have seen stuff on the internet suggesting the use of  Sodium Carbonate instead of Sodium Bicarbonate. Not sure if my C-Tek would work as the charger though I think I still have my original charger in my loft unless I chucked it. I have nothing to loose I guess so might give it a try.
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Offline Lobo

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Re: Why can't you have rusty petrol tank shot or bead blasted ?
« Reply #3 on: September 04, 2020, 10:12:51 AM »
Yup, I too have had big success with electrolysis and inner rust removal....

Offline AshimotoK0

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Re: Why can't you have rusty petrol tank shot or bead blasted ?
« Reply #4 on: September 04, 2020, 12:54:59 PM »
I guess the reason nobody seems to media blast tanks inside is the problem with removing every trace of media afterwards if it's the grit/glass type. Having said that however, people rattle stones or gravel around and that must shed some abrasive dust which is just as bad although could be dissolved in acid I suppose.
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Offline SumpMagnet

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Re: Why can't you have rusty petrol tank shot or bead blasted ?
« Reply #5 on: September 04, 2020, 07:12:36 PM »
Top tip for people wanting a 12V power supply ..... If I remember rightly...the yellow output leads from PC power supplies are 12V. Black is the common ground.

I used one to make a 12V DC supply for a hobby charger power supply. You bundle together the yellow leads together to form a single output. Mine was a 450W supply. At 12v, it will handle 35A draw. It was sitting in the shed gathering dust. Lots of YouTube vids on how to do it.
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Offline Macabethiele

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Re: Why can't you have rusty petrol tank shot or bead blasted ?
« Reply #6 on: September 04, 2020, 08:46:58 PM »
I've ordered the Sodium Carbonate, I gave my old 4 amp trickle charger to my brother so I will borrow it back from him as I have sold all my old PC's. I will post pics of the froth once I get started! :D
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Offline Rob62

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Re: Why can't you have rusty petrol tank shot or bead blasted ?
« Reply #7 on: September 05, 2020, 11:52:24 AM »
I have used this technique in the past with great success... But watch out, last time I mentioned it on here i had one of the resident “experts” telling me it didn’t work... even though it did 😄

Offline SteveW

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Re: Why can't you have rusty petrol tank shot or bead blasted ?
« Reply #8 on: September 05, 2020, 12:49:04 PM »
I think the trick is to leave it hours to do its thing, keep water topped up.
Think I put a bit more bicarbonate in half way through as well.
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Offline Rob62

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Re: Why can't you have rusty petrol tank shot or bead blasted ?
« Reply #9 on: September 05, 2020, 12:51:44 PM »
Yep.... i left mine overnight, although i must admit i was a bit nervous of leaving it... The amount of crap and rust that came off was amazing though..

Offline SteveW

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Re: Why can't you have rusty petrol tank shot or bead blasted ?
« Reply #10 on: September 05, 2020, 02:32:48 PM »
Be careful though, the bubbles produced are hydrogen.
I did mine outside over a couple of days.
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Offline AshimotoK0

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Re: Why can't you have rusty petrol tank shot or bead blasted ?
« Reply #11 on: September 05, 2020, 02:59:16 PM »
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.
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Offline the-chauffeur

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Re: Why can't you have rusty petrol tank shot or bead blasted ?
« Reply #12 on: September 06, 2020, 12:25:52 AM »
Quote
Why can't you have rusty petrol tank shot or bead blasted?

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 . . .

« Last Edit: September 06, 2020, 12:29:15 AM by the-chauffeur »

Offline Macabethiele

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Re: Why can't you have rusty petrol tank shot or bead blasted ?
« Reply #13 on: September 06, 2020, 09:45:02 AM »
Quote
Why can't you have rusty petrol tank shot or bead blasted?

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 . . .

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.
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Offline mike the bike

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Re: Why can't you have rusty petrol tank shot or bead blasted ?
« Reply #14 on: September 06, 2020, 09:57:10 AM »
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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