Unsuitable metals

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Unsuitable metals

This topic has 12 replies, 11 voices, and was last updated 13 November 2024 at 20:16 by JasonB.

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13 November 2024 at 13:48 #764209
Dalboy
Participant
@dalboy
I am making a aluminium fuel tank for my Farm Boy engine is there any metal not suitable for fitting to go into the tank
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13 November 2024 at 14:14 #764214
Howard Lewis
Participant
@howardlewis46836
If the tank is Aluminium, there is always the danger of electrolytic corrosion caused by dissimilar metals being in contact when moisture is present. (Atmospheric, or accidently within the fuel)

Copper containg alloys are always suspect where Aluninium is the other constituent

May I suggest making unions and taps from Aluminuium, and using a plastic pipe to carry the fuel.

In this way, there will be electrical connection between the two metals

You can use brass connections elsewhere, but without contact withe Aluminium tank.

HTH

Howard
13 November 2024 at 14:52 #764226
Charles Lamont
Participant
@charleslamont71117
Sorry, Howard, I know we should not take the pee out of other peoples typos, but I am quite taken with ‘Aluninium’, to be defined as “a lightweight metal, used unwisely”.

I am not so sure about ‘Aluminuium’, but I think it may be “a lightweight metal used, perforce, for a rush job when there is nothing more suitable to hand”.
13 November 2024 at 15:13 #764227
noel shelley
Participant
@noelshelley55608
316 Stainless steel, fittings are commercially available. Noel.
13 November 2024 at 15:58 #764247
JasonB
Moderator
@jasonb
Loads of IC engine designs from years gone by that have brass and bronze bearings, tappet guides, venturis and other fittings into the aluminium. Never heard of problems with any of them. The likes of Westbury, Sparey, Stuart, Whittle, Stride and all were happy to use these metals together. Not to mention all those Weber and SU carbs out there that have brass fittings into the ali.

Use what you have.

If you are plumbing between the two with “Plastic” then use Tygon not the usual silicon that is often used for RC glow fuel engines as the silicon swells

A few examles with brass and bronze in contact with aluminium
13 November 2024 at 17:02 #764251
ChrisLH
Participant
@chrislh
The important bit is that the copper bearing alloy and the aluminium should be in contact with an electrolite (e.g. water) to experience electrolytic corrosion. I know because I’ve done it. Used brass cooling water fittings on my Wallaby twin resulting in masses of white fur appearing on the ali. bits.
13 November 2024 at 17:07 #764252
Dave Halford
Participant
@davehalford22513
Might that have been monkey metal rot?
13 November 2024 at 18:14 #764283
File Handle
Participant
@filehandle
When using different metals in contact with water (impure) it is always wise to be aware of the electrochemical series. https://www.chemguide.co.uk/physical/redoxeqia/ecs.html
You are basically creating an electrical cell by using different metals. The further apart they are in the series, the quicker they will react.
13 November 2024 at 18:16 #764284
Nigel Graham 2
Participant
@nigelgraham2
Aluminium and steel can be poor together, even worse with stainless-steel, but that is when the junction is in even slightly impure (so conductive) water.

The aluminium is the one that corrodes.

(A point perhaps to consider when using aluminium-alloy extrusions and steel fishplates and fastenings for miniature-railway rails?)
13 November 2024 at 19:39 #764304
old mart
Participant
@oldmart
Aluminium tanks were common on motorcycles when they were customised as street racers and nobody would have ever thought of making a corrosion proof tap, brass was the commonest with zinc alloys a close second. Same with steel tanks.
13 November 2024 at 19:50 #764311
Georgineer
Participant
@georgineer
On 13 November 2024 at 14:52 Charles Lamont Said:

Sorry, Howard, I know we should not take the pee out of other peoples typos, but I am quite taken with ‘Aluninium’, to be defined as “a lightweight metal, used unwisely”.

I am not so sure about ‘Aluminuium’, but I think it may be “a lightweight metal used, perforce, for a rush job when there is nothing more suitable to hand”.

Not to hijack the thread, but in my days as a secondary school science teacher I collected spellings, partly to try and understand where the difficulties lay. I amassed 47 different spellings of aaiminiummiu. The runaway winner was fmomiter with 112 variations.

George
13 November 2024 at 20:00 #764314
Dalboy
Participant
@dalboy
I probably go with brass from what I have read here. Thinking about it, when building the Farm Boy engine components there is brass in contact with Aluminium parts, so should not be a problem. Today I managed to complete the second support and other end cap. I will get some photos and put them in my build thread.

Thank you all for the feedback on this.

@JasonB not sure but could not see any photos
13 November 2024 at 20:16 #764317
JasonB
Moderator
@jasonb
Sounds like the usual forum problem of photos added during an edit not showing, they may appear tomorrow.
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