chemistry question

Grant Erwin · 2003-10-31T18:33:47+00:00

I've just cleaned a bunch of pieces of new black pipe by soaking themin a hot TSP solution. They don't feel oily, and the lettering is gone,but they are still vaguely black in color. I have read many times thatgiving steel items a light etch in phosphoric acid will leave a thinplating of iron phosphate which is a good strike coat for painting.Since there are phosphate ions aplenty in TSP, might I have justgotten the desirable iron phosphate coating without having to find abunch of phosphoric acid?Second question: unfortunately, these parts aren't going to be painted,they're going to be galvanized. The galvanizing shop is real leery ofitems fabricated from black pipe because of the coating they get -that's the reason for the TSP dip in the first place. I'm consideringa light etch in some dilute HCl (muriatic i.e. hydrochloric acid)which should completely remove any doubt on the galvanizing shop's mind.Question: can I neutralize HCl with TSP? I know that TSP in solutionis basic. I'm just wondering what happens when you mix TSP with HCl -obviously, you'd get Na+ ions, H+ ions, PO3-- ions, and Cl- ions.Sort of like a mix of phosphoric and hydrochloric acids, except forthe sodium. I can't figure it out, my college chem days are long over.Final question: assuming #2 does NOT work, and further assuming it'sbad news to dump TSP into the sewer, is there any easy cheap way toneutralize the TSP and make it less environmentally harmful? Myneighbor, no dummy, suggests using it as fertilizer. Does that makeany sense?Grant ErwinKirkland, Washington

Oct 31, 2003 40 Replies

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George E. Cawthon 22 years ago

True. But TSP/90 sounds like 90% TSP, so I would think this is a near case of labeling fraud.

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