Chemical Dipping

[maldotcom2]

So i got tired of using degreaser and a toothbrush to clean an entire engine, so i researched chemical dipping. This is generally an industrial process in which iron or steel engine parts are cleaned by lowering them into a solution of hot sodium hydroxide and sodium carbonate.

I've decided to do this at home using a large tub. Is there any reason to avoid this process?

[Kal123]

I'll let Walt answer this one.

YouTube - Breaking Bad - Emilio's Acid Bath

[maldotcom2]

Haha very appropriate. However Caustic Soda is a lot safter than hydroflouric acid.

I gave it a whirl, lots of bubbling ensued and the grease and dirt was quickly stripped away. I now have a manifold which is clean but for some reason coated in a grey residue which i have to scrub off. So i'm not sure whether i gained anything, i'm still having to scrub the damn thing with a brush.

Does anyone know what this grey stuff is? Can i make a second bath that will disolve that? Phosphoric acid maybe?

[jujibelly]

Clearly you didn't learn your lesson the first time.

[maldotcom2]

If the lesson was to give up, hell no. Trial and error, it's all fun and games.

[maldotcom2]

Ok i got some phosphoric acid, works pretty well to get the grey stuff off. The only issue is the price, so i'm hunting around for it cheaper. It's sold as aluminium cleaner or stainless steel cleaner. My plan is to have 3 bath's, first the caustic bath, then the acid bath, then a soak in fresh water.

[Tsunamix]

The grey residue is aluminium salts, specifically aluminium hydroxide or ALUM.

It's soluble in both acids and alkalines, particulary HCL Hydrochloric Acid And H2SO4 Sulphuric acid.

Theoretically, good old battery acid will take it off. So will ammonia solution, or even pool chlorine.

[Matt_vp]

I have used alibright but you have to have the mixture right and if you leave it in to long it changes colour from clean alloy to yellow to grey to black i think.
Bead blasting works well.
Matt

[maldotcom2]

Thankyou so much Tsunamix. It's kind of embarassing but i didnt even realise the manifold was aluminium. Thought it was cast iron like the rest of the engine. Can't believe i didnt check.

Well i guess i'm not going to have this problem when i dip the heads and block in the caustic solution. In theory they should come out clean. So i'm not going to need any more acid baths.