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Hot tank Solution

 

I was wondering if anyone could help me out. I have a small home shop where I rebuild engines, mostly for the local race circuit. I am in the process of fabricating my own hot tank as the machine shop tanks only use a mild caustic (lye) solution and they do a very poor job of cleaning/descaling blocks and heads. I would like to use a cost effective acid solution such as the 30% muriatic solution which can be purchased at the local Home Depot, however I am concerned about hydrogen embrittlement in the cast iron especially the main cap/web areas of the block. Would this be a problem?

The last question is if this is a suitable solution to use how would you neutralize it for disposal when it is spent and no longer effective?

Any help would be greatly appreciated as I am tired of spending $60.00 for a hot tank only to bring the block home and have to spend several hours of manual cleaning to remove the remaining rust/scale.

Jeff Monell
- Riverview, Florida

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Hi Jeff,

Firstly, please have a look in the archives at # 12044 because this mentions muriatic, sic. HCl and discusses neutralization.

A 'hot' tank with HCl. Ugh. Firstly, you'll have a fuming problem. In other words you'd need good ventilation. Secondly, HCl will attack stainless with impunity, let alone mild steel and the attack increases with temperature. So how 'hot' is your tank? If max. l40 degrees F (some mfgs say l50, others max l70), you could use a Polyethlene MOULDED tank ... but for the higher temperatures it would have to be reinforced OR sitting inside a water filled m.s. tank ... with, obviously, enough liquid in it to prevent it from floating !

Re hydrogen embrittlement in the cast iron, I'm not a chemist but would have thought that this would be very inconsequential IF you neutralized the block with an alkaline afterwards.

Moulded Poly tanks are inexpensive. They range from 2 gal. to l50 gal. rectangular and up to 500 gal (in Canada, anyway) round with an open top.

I hope that this is of some help to you.

Freeman Newton [deceased]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).