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Tank cleaning / derusting
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Concretecow
Milton Keynes
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April 28, 2019 - 9:51 pm
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I've been trying this over the last few days.  It's working like a charm. I say working, because I'm going to give the acid stage another go (my rust was very thick and very stubborn).  

Firstly, I'd say it's worth taking the time for the caustic soda "gunge removal" stage, as this really allows the Spirit of salts (as it's still rather quaintly referred to - Hydrochloric acid to you and me) to attack the rust.  Aggressive a chemical though it is, it doesn't really touch oil or grease ("gunge"). I left the caustic solution in there for about 5 days in the end, with no ill effects, agitating a couple of times a day.  I would add a caution about disposal.  Hold the tank low down when you tip the solution out.  You don't want it to splash up onto your skin, and it will eat your clothes.  If you're not wearing gloves, and you get it on your hands, wash it off with lots of water.  That soapy feel when you rub your fingers together, that's saponification - the caustic turning the fat in your skin into soap.  This can generally be considered a BAD THING embarassedand no substitute for Imperial Leather.  

I fitted a steel bolt in the petrol tap hole.  I'm certain the fine brass mesh of the filter wouldn't survive.  For the acid stage, I can't stress the warning enough - ALWAYS POUR IN THE WATER FIRST, THEN THE ACID.  The tank gets quite hot with the addition of the Spirit of salts to the pint of water, but don't panic.  Have a large bucket of water handy to rinse out any spillage, and the whole operation is best conducted in a plastic container in case of pinholes or leaks.  Also have a well soaked rag to mop up anything that drips from under the rim of the filler cap as you release the pressure build up.  This is particularly important if you have a half decent paint job that you want to preserve.

The other posts about using vinegar and coke etc., I'm sure work to a degree, but there's no substitute for using the stronger chemical versions - all perfectly safe if you wear an apron/overalls, gloves and safety glasses, and have copious amounts of fresh water to hand to swill down any spillage.  Always wash the chemical off yourself first, and worry about your precious tank afterwards.  

I'm sceptical about using a tank liner, I'm concerned that if it breaks down, it'll be harder to clean the tank in the future but I shan't be etching with phosphoric acid either.  My grandchildren will just have to de-rust it again in another 70 odd years. rofl

The chemicals (caustic and acid (enough for 2 treatments) are available for about £15 from a well know online retailer named after a South American river.  A little more expensive than Asda vinegar or Aldi phosphoric acid, sorry, I mean cola, but they do a better job.  I'd certainly encourage anyone to try it.  As we speak, the tank is undergoing a final drying process at the back of the airing cupboard.  My wife doesn't know, but I'm worried the faint smell of petrol might give it away.  I just need it thoroughly dry to prevent any further corrosion before I attack with acid again next weekend.

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BSAdave
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April 30, 2019 - 8:22 am
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Sounds well dodgy to me , Acute (short-term) inhalation exposure of Hydrochloric acid may cause eye, nose, and respiratory tract irritation and inflammation and pulmonary edema .

Use this method at your own risk. I prefer to use the much safer method of rust removal using Electrolysis, clean and no nasty chemicals involved the waste product can be disposed legally down the drains.

Each to there own.

I could agree with you, but then we would both be wrong

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BASIL
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April 30, 2019 - 9:59 am
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Hi, I use warm caustic soda solution and a battery charger usually derusts a tank in less than an hour without any problems. Regards Basil.

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cocorico
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April 30, 2019 - 12:21 pm
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BSAdave said
... I prefer to use the much safer method of rust removal using Electrolysis, clean and no nasty chemicals involved the waste product can be disposed legally down the drains.

Each to there own.  

BASIL said
Hi, I use warm caustic soda solution and a battery charger usually derusts a tank in less than an hour without any problems. Regards Basil.  

Bear in mind that electrolysis also uses a strong alkali as the electrolyte (though maybe safer than a strong acid).

I've used electrolysis successfully, but also find white vinegar effective. The main thing, whatever you use, is to read the safety instructions, wear appropriate clothing, use lots of water to dilute the residue and TAKE CARE.

1956 D3 in the back of the barn with 6 other bikes ahead of it!

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Concretecow
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April 30, 2019 - 10:41 pm
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BSAdave said
Sounds well dodgy to me , Acute (short-term) inhalation exposure of Hydrochloric acid may cause eye, nose, and respiratory tract irritation and inflammation and pulmonary edema .

Use this method at your own risk. I prefer to use the much safer method of rust removal using Electrolysis, clean and no nasty chemicals involved the waste product can be disposed legally down the drains.

Each to there own.  

Dave, you're absolutely correct about the exposure to hydrogen chloride.  However, a large proportion of my post was about precautions.  I carried it out in the open air, and didn't even smell it since the fuming of the dilute solution of 30% hydrochloric acid is a) minimal, and b) easily dispersed outside without the risk of a plume developing that will necessitate evacuating the neighbourhood.  Don't forget, Hydrochloric acid and Phosphoric acid are sold mail order as common drain unblockers, same as your caustic soda, so can also safely be disposed of down the drain.  I didn't mention it, but I also wore safety glasses, and informed the rest of my family what I was up to, and not to come near.  Although my teenage daughter took a keen scientific interest in the reduction of the ferric oxide by the hydrochloric acid.  I even had to dig out the chemical equation for her.  She was amazed at the result, and fascinated by the practical application of basic chemistry.  One point to Dad.  

From my high school chemistry, doesn't electrolysis of Sodium Hydroxide produce explosive Hydrogen gas at the cathode?  If so, in sufficient quantity, if ignited by a spark from the charger inside the tank, it may well douse the user in highly alkali caustic soda solution.  Oh, and please don't state or imply that caustic soda is safe and is not a nasty chemical.  It is.  Very.  Alkali burns are actually worse than acid burns, particularly splashed in the eye.

Just shows, whatever method is employed, you should know and understand all the risks involved and chemicals should always be treated with respect, and handled with caution.

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swalsh58
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April 30, 2019 - 11:01 pm
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I don’t believe they use caustic soda but soda bicarbonate - washing crystals. It’s the electrolysis that removes the rust. The solution is just the conduit. So I am led to believe....

Current bikes......1958 D5, a 77 Suzuki GT250 and a 77 Honda CB125S. I have a 74 Kawasaki S3 400 and a B175 waiting for restoration. A 1980 Honda CB400N waiting for MOT.  Everyday ride is a 2011 Harley Davidson Sportster. 

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BSAdave
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May 1, 2019 - 8:41 am
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When i do it no nasty chemicals , just washing soda . Just pointing out the dangers of your method.

I could agree with you, but then we would both be wrong

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Concretecow
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May 1, 2019 - 7:12 pm
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BSAdave said
When i do it no nasty chemicals , just washing soda . Just pointing out the dangers of your method.  

Ah, I had read Cocorico's post which had amalgamated both yours and Basil's posts.  It was Basil that was using the caustic.  I thought you were using the same chemicals and method.  Sodium Bicarbonate is an entirely different beast altogether.  It is safer, but as we both agree, there are dangers in using chemicals if the right precautions are not taken.  Although to be honest, the stage of the process trhat I hadn't properly risk assessed was leaving the tank in the airing cupboard to dry......

Cheers

Concretecow

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