Electrolysis method to clean up an old exhaust manifold?

[petergarth]

Hi All

I'm busy doing a complete overhaul of a 30 year old Volvo Penta 2002 and have been posting questions over the last few weeks with lots of help from the forum.

While waiting for parts I'm doing a clean up of all components.
The exhaust manifold was particularly rusty internally and full of carbon build up.
I suppose that's not surprising on an old raw water cooled engine despite regular anode replacements.

I've got a lot of it off by using vinegar and then getting bolder using hydrauchloric acid (cautiously) and elbow grease.
But I can't really get to the inner water channels that takes water down the two tubes which join the exhaust gas.

I just had a thought, in the past I've used a battery charger and electrolyte bath (Washing soda or Bicarbonate of soda) to clear up rusty tools.

Has anyone tried this method to clean up things like an exhaust manifold????

It seems like a good idea and less drastic than my hydraulic acid bath!

 

[Mister E]

I haven't used this method but if you do could you please post an update.

 

[penfold]

Electrolysis isn't much good for internal derusting as there is a 'line of sight' aspect to it(presumably the ions get lost en-route or something) and for interiors you need an electrode that goes into the space that needs treatment. Pickling is a lot easier for this job.

 

[rotrax]

Caustic soda is used for carbon removal in motorcycle two stroke exhaust systems.

Fine with cast iron or steel. Mix the crystals, leave the part immersed. WEAR GOGGLES!

Not for aluminium it is'nt there after a while.............................

The other way is to burn it out using oxy acetylene.

Get the carbon glowing, turn off the acetylene. The oxygen soons burns the glowing carbon away.

 

[vyv_cox]

Hydrochloric acid in the typical strengths the public can buy it will not attack steel or cast iron on immersion. I would not advocate leaving it for hours but a few minutes is normally sufficient for the mixture of carbonates and carbon that accumulate in sea water passageways. The bubbling of CO2 gas that you see is from the deposits, not the metal.

 

[petergarth]

Thanks everyone for the thoughts.
I did try the electrolysis for a few hours checking all the time. I take the point about line of sight but it seems to have done some good in the places I can see. It's now about as good as gets for an old manifold and I''m going to repaint it tomorrow.
The manifold is something I can replace in-situ later so I'm not stressing too much. It should last a good few years more.
Should have my parts by the end of the week. It seems the Southern tip of Africa really is a long haul for DHL. But they are on the way.