Bentley rotary. Rust removal.

Hello.

My father is building a Bentley BR2 on and off. Its been a while since he did anything to the engine and has found the main crankcase is rusted due to the embryo crank beside it 'sweating'. The crank is really rusty. The bits were all in a box in the bedroom, all were lightly oiled and wrapped in workshop tissue paper.

The rust covers 1/4 of the front of the crankcase and its not looking good, awful actually considering the hours of work.

The rust is now slightly pitted black scale, can this whole part be recovered? Nickel plating maybe? Fortunately its only the one part affected, the thrust box is ok and so is the cambox and nose. We don't think a skim is worthwhile or safe as the part was finished size.

Cheers,

Simon

Hi Simon,

I too have been building a Bentley off and on for far too long and I know just how your father must feel having discovered the rusting.

If it's badly pitted there is nothing you will be able to do to restore the surface finish without recutting. Nickel plating will just plate what is there and in all probability accentuate the problem besides being totally out of character for the engine.

I have always found the coarser Garryflex abrasive blocks used with paraffin as a lubricant ideal for rust removal but even they can't do anything about any deep pitting effect left other than polish out the 'recesses'. The only way in my experience that that can be overcome is, as said, by recutting the metal but if the pitting is not too deep using wet and dry paper of varying grits stuck with doubled sided tape to small blocks of smooth hardwood (model aircraft engine bearer is ideal) and a bit of patience may help even things out a bit before using the Garryflex.

As a matter of interest I have the various steel parts made (all En1a for the case parts) stored for several years coated with a mixture of paraffin and oil and wrapped in waxed paper stored in card boxes. I began it (much to my chagrin) in 1992 and only once has a small amount of rust been found on the rear thrust box which was easily dealt with as above. It occasionally sees the light of day when a quick inspection and re-oil sees it ok for another few months - this is a timely reminder to perhaps have another check

I haven't worked on it for some time now and am not sure when the opportunity will come when that might be again - shame really as there's a lot of work been done so far but neither the time nor the inclination to do so is there at the moment.

Hope you manage to resurrect it sufficiently to meet your 'eyes approval' - it's a lot of time not to mention swarf to make another!

Hope this helps a little

regards - Ramon

Edited By Ramon Wilson on 02/12/2012 23:18:40

Try electrolysis. I have used this for several rusted parts and it works very well at removing all corrosion but it will obviously not remove pitting.

It is a simple and very safe technique using only a plastic bucket containing very dilute cold washing soda solution, a 12 volt battery charger and a scrap steel cathode plate. Google "rust removal by electrolysis" for full details from mostly American sites as it is a very popular method there.

The beauty of this process is that it does no harm at all to the surface as abrasives would. Try it first and if the surface is still unacceptable then you can always revert to abrasives.

When storing machined steel components be very careful what paper you use for wrapping as many grades contain acid residues. Always oil the surface (not with WD40) I use 3 in 1 and then wrap the parts in proper VCI paper. I can help you with VCI paper .

One of the best oils for rust protection is Camellia oil - used historically by the Japanese to preserve tools and swords (Also for Sumo Wrestlers hair dressing ). It is expensive to buy for this purpose but is also sold for essential oils use more cheaply. eBay is a good source. I use it on my machine surfaces and can only report good results.

Another oil for rust prevention is of course Lanolin which was used extensively in industry for preventing rust on bright Steel and tubing, it is a by product of wool production - sheeps fleece contain it.

Best regards

Terry

Axminster Tools sell Camellia Oil, used it for years, a quick spray on your chucks etc keeps them like new.

Lampton, please note that the electrolytic method of de-rusting can/will cause hydrogen embrittlement of steels.

Lampton, please note that the electrolytic method of de-rusting can/will cause hydrogen embrittlement of steels.

Yes this is a possibility with some high strength steels but the effect can be mitigated by limiting the current used and by heating the component at 100 C + for a while after treatment.

The system is perfectly safe on mild steel and cast iron.

Lots of info on hydrogen embrittlement & its prevention/correction on the Internet

Must be good ...never seen a rusty sheep

There were\are quite a few formulas used by the Japanese to preserve sword blades and the like. One western approximation is a mixture of light mineral oil and clove oil. It's got the advantage of being relatively cheap - but the smell of the cloves might not suit everyone, it's fairly pungent.

A agree with the suggestion of electrolytic rust removal. I was given a 'basket case' half-finished seal, and used it to clean up the very sorry looking crankshaft. The rust was converted to black phosphate.

You would not believe the condition of this before I started:

Don't forget to oil it as soon as it comes out of the bath. I used caustic soda, I understand that even sodium bicarbonate (baking soda) works just as wel as either caustic or washing soda and much better if you spill it!

Neil

I am pleased that Stub Mandrel has used the electrolytic rust removal method successfully..

May I make a few comments?

1. In my earlier contribution I said the scrap steel electrode was the cathode this was a "senior moment" it should be the anode i.e. connected to the positive side of the supply.

2. The black deposit is not phosphate but Fe3 O4 ferric oxide which loosely adheres to the surface. In theory the process should reduce all the complex rust deposit back to metallic iron but in practise this does not happen. The chemistry of rust and its reduction during electrolysis is complex and the subject of academic argument. Don't worry about it just gently clean off the black deposit using fine 3M abrasive pad under running water. Dry the item with a paper towel then oil the surface immediately.

3. There is no need to use caustic soda or other corrosive electrolytes 15g/l (approx. one table spoonful / gallon) of ordinary washing soda in cold water does the job. It is only there to make the water conductive. At this concentration the electrolyte will not cause any harm to either the operator or the environment. The electrolyte becomes very dirty during the process and acquires a brown scum on the top don't worry about this it can be used many times so don't throw it away if you have other bits to clean .

I use a tumbler for small pieces using steel media and burnishing powder. It gets rid of all corrosion even in the pits and shines just like polished steel. If you want a matt finish use ceramic shapes, ideal for deburring as well. For larger items I use a large coffee tin in the lathe. I have been restoring a lathe and have cleaned all the headstock and gearbox items using this method. I also use it to restore bits on my m/c's as well. Just load the drum and leave it all day to tumble and get on with something else. I have used this method for 20 plus years with great results. The great thing about it is you are not restricted to any particular material or media. Even crushed walnut shells do a good job on brass and other soft metals.

lambton is right of course, there is nowhere for the phosphorous in phosphate to come from!

What it is is also known as 'magnetite' and it has amuch more compact form than rust (hydrated ferrous oxide which is MUCH bigger than the original metal due to the incorporated water molecules).

It should adhere strongly to the parent metal and give a result which is dimensionally very close to the original (if the corrosion hasn't been severe). Magnetite can be used as a rustproofing coating for inside steel boiler watertubes. I wouldn't bother trying to remove it unless there is unacceptable surface deterioration.

Neil

Lots of good advice given - no response from OP Simon?

JD

Why not have the crankcase soda blasted? I do this on most of the engine builds I do including cylinder heads. Leaves a beautiful vapour blasted finish, all corrosion is removed and it just hot tank washes away leaving a perfect casting ready for painting or assembly.

Can help if you want me to.

mike

Mike,

I bead blast crankcases too - usually ali though - and agree on the lovely uniform finish it gives and that it will soon remove surface rust on steel too. It won't eliminate average tool marks however so I doubt it would disguise the pitting described by the OP.

I notice you use the word Soda - is this using Bi Carbonate ? I have recently been made aware of this but haven't tried it yet. Are you able to comment on how it compares (surface finish) to bead blasting?

Jeff, I guess we have to assume Simon hasn't returned to see the response to his question - otherwise what else could one think

Regards - Ramon

Its only been 4 days and questions are being asked about my lack of response, so here goes.

I don't go online much as I'm short on time, I can get email at work and have seen the replies as alerts but can't use forums on a work pc. I can only login at home and this is my 1st opportunity.

Most of the replies fail to appreciate the Bentley, it is an engine that demands a high level of appearence as well as its running condition, the part needs to be perfect. A skim would weaken it, blasting may help but it would need further metal removal to clean up the finish from blasting. Can't do any hot work, its completely finished and all mating parts are also finished. Electrolytic cleaning leaves black marks? We're already at the black mark stage, I hoped someone would be able to help with the idea of plating. Plated then emery polish in lathe to simulate finely turned finish? I can't find much info online about plating damaged parts.

From what dad has been saying I think he's simply going to make another crankcase, no one would ever be happy making a Bentley and having a major part flawed in any way. I don't think he ever wanted to make a show winner but I know he has standards and he's not happy.

OK Simon, I appreciate your situation but responses on here to a plea for help usually come by return.

From what you say I don't think you have fully appreciated the attempts to help you.

Firstly as a Bentley builder myself I can well appreciate your fathers feeling and can empathise with his situation.

Having made a similar crankcase I can well appreciate the work involved and as someone with a degree of past experience can only offer the advice given so far. However, for what it's worth plating is like painting - the surface finish will only ever be as good as the substrate underneath. In your case this is damaged and to do as you suggest would require either the ability to plate the area damaged and then reclaim it by abrasive means leveling it to the surrounding area before plating it again to get a uniform finish. A bit like trying to paint a surface and reclaiming areas where the paint has flaked off back to the parent surface only in your case theres not the ability to cover that final surface with an opaque colour. I'm sure you can see that's not something that probably most of us on here would recognise as a reasonable way of going about things given the part.

To that end I think your fathers decision to make another is the only effective way to get over the problem as whatever you do to reclaim it will as you say potentially either weaken the part or change it dimensionally at the expense of visual perfection.

I confess to being someone who does not like 'imperfect' things and in this case I would very much follow in your fathers footsteps and make it again - if it's any consolation I made three cam boxes and, as I'm sure he will agree, theres an awful lot of work in them too.

I do wish him luck with it - I only wish I could find the time to finish my own.

Regards - Ramon

Well the ideas get appreciated by others too so it doesn't matter if the OP can't get back for a while. I must have a go at this electrolysis method.

I'm lucky enough to have significant access to the internet at work. Coming onto the forum is a great relief when on a boring conference call. They even recently removed the block on ebay bidding.

"I can't find much info online about plating damaged parts."

I don't know much about it, but would metal spray work to build up the damaged / pitted sections, it could then be taken back to origional size, and finish, just a thought, may be a bit daft, someone will know if it's practical. Ian S C