chemistry question

I've just cleaned a bunch of pieces of new black pipe by soaking them in 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 that giving steel items a light etch in phosphoric acid will leave a thin plating of iron phosphate which is a good strike coat for painting. Since there are phosphate ions aplenty in TSP, might I have just gotten the desirable iron phosphate coating without having to find a bunch 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 of items fabricated from black pipe because of the coating they get - that's the reason for the TSP dip in the first place. I'm considering a 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 solution is 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 for the 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's bad news to dump TSP into the sewer, is there any easy cheap way to neutralize the TSP and make it less environmentally harmful? My neighbor, no dummy, suggests using it as fertilizer. Does that make any sense?

Grant Erwin Kirkland, Washington

Reply to
Grant Erwin
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Hi Grant,

I can't answer the first part of your post, far too long since I had chemistry classes as well.

TSP alone is just fine as a fertilizer. It's the same stuff that used to be in laundry detergents. It was banned in that application because of the algae blooms it caused once the treated waste hit the rivers and lakes. Remeber "Phosphate Free" stickers? It's just the "P" of the KNP rating for fertilizer.

The only concern is what else is in the solution. I cook down the TSP solution used for stripping old tools (likely lead based paint) and put the sludge in a sealed can with kitty litter. It can then be turned in at the local landfill just like old lead based paints, in the hazardous waste disposal area for home owners. If the solution has a fair bit of oil in it you may want to do the same thing, sort of hard to grow grass over an oil spill :-(

Cheers, Stan

Reply to
Stan Stocker

Disclaimer: I am a chemistry ignoramus.

That being said, the reason they took TSP out of laundry detergent is that the phosphate is a fertilizer that caused some spectacular algae blooms in wastewater treatment plants. The little bit you're going to add won't do squat.

I toss a couple of tablespoons of the stuff into the washer, along with the regular detergent, to wash my son's filthy sports uniforms. Now, if I could only get back the enzymes that were in there until around 1970 or whatever, we could be as clean as we were in 1968!

Ed Huntress

Reply to
Ed Huntress

It's very caustic. However, you should see it get the sweat and grime out of my baseball caps. Normally, I can hardly touch them with boiling lye.

Suggestion for marital harmony: don't put your baseball caps in the dishwasher while your wife if looking.

Reply to
Ed Huntress

Ed I know some of the dishwasher soap has enzymes in it, my wife swears by it. Wonder how it would work on clothes. Lane

Reply to
lane

I"m no chemistry wizard, but my years of precious metal refining taught me a few things about hydrochloric acid and metals. I think I'd use a dilute solution of hydrochloric to clean the steel parts you want to galvanize, then neutralize the parts with sodium hydroxide (lye). That will prevent the instantaneous rusting you would otherwise get. I used to run a small ball mill. So long as I kept the interior basic (9 pH or higher), there was no rusting.

If I'm not mistaken, when you take parts to be galvanized, they are subjected to an acid wash prior to receiving the zinc dip.

Harold

Reply to
Harold & Susan Vordos

And if you put motorbike transmissions in the oven, be sure to use those Reynolds "roast-in" bags to keep the

90 wt fumes from escaping.

Jim

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Reply to
jim rozen

I think this is pretty good advice. The base will neutralize any acidity. The TSP is not really a base, IIRC it's like most detergents, being a large molecule that is polar at one end, and non-polar at the other end. So the polar end grabs onto the water, and the non-polar end grabs the oil or grease.

I also suspect that simply rinsing the parts well, and using a mild base like baking soda will be enough, so he would not have to deal with caustic NaOH solutions.

Jim

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Reply to
jim rozen

I'm afraid I'd have to strongly agree, Jim.

One of the negative experiences I had when refining was to get a drop of nitric acid directly in one eye. Immediately the surface of my eye peeled off. I had done something EXTREMELY stupid in that I had gone from the machine shop, where I always wore safety glasses, to the lab, where I removed them (??) while I tended to a large beaker of silver, to which I added some acid. One drop, and only one drop, popped out of the beaker, right into my left eye.

When an ophthalmologist looked at my eye, he told me how "lucky" I was. I was told that the human body can quickly neutralize acid, which prevented the acid from doing permanent injury to my eye. On the other hand, he said that had the drop been lye instead, I would have been blinded because the lye continues to destroy tissue. We can't neutralize base solutions nearly as well.

I endorse the baking soda, and would encourage anyone facing this situation to use it in place of lye.

Oh, yeah. Just as I was promised, the eye healed up with no lasting effects, although I've often wondered if that's the reason my arms are too short now. :-)

Harold

Reply to
Harold & Susan Vordos

AAAAAAghhhh!!!

I'm sure glad I already ate. This story is was only

*slightly* less less horrifying than Roy's fire extinguisher tale.

Because I see folks work with chemicals all the time at work, and see how they do so under fume hoods, and with goggles and whatnot all the time, I tend to have about one reaction when I hear about things like this, to pass out on the floor.

Yep, a lot of this stuff is pure habit. I see the researchers do stuff with machinery, using no eye protection at all - and they're the same folks who won't work under a hood unless the sash is pulled most of the way down, and they've got eye protection on all the time.

Jim

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Reply to
jim rozen

I am a chemist so I will try to clear up a few comments here. (Though I know little about treating metal for galvanizing.) First TSP is not a soap with a polar end and a non-polar end. It is just tri-sodium phosphate, Na3PO4. This is the basic form of phosphoric acid, H3PO4. So TSP is a base and can consume three equivalents of HCL, which would produce H3PO4 and 3NaCl. This resulting solution would be quite acidic. The key to neutralizing the HCl would be to use excess TSP so the solution always remains somewhat basic. Sodium hydroxide, NaOH, will do the same thing, but it is more basic and dangerous than the TSP. In any case expect the solution to give off heat as you neutralize the acid. So add the acid slowly to the base, while stirring the basic solution. This should minimize any heat build-up.

Good-luck,

John

Reply to
Me Mine

YO, John!....

This is a little like asking a doctor for medical advice over lunch, but...

When we use HCL to clean rusted steel, or to strip the galvanizing off of electrical steel tubing, how should we neutralize it to prevent further (accelerated) rusting? We've heard that dipping it in a lye solution will leave NaCl in the pores of the cleaned metal and will lead to further rusting, but we (I) wouldn't know the facts if our (my) life depended on it.

What's the story? Thanks, doc...

Ed Huntress

Reply to
Ed Huntress

Well that clears that up.

I guess as a crank turner I'm not that good a chemist! Sorry for the confusion, guess I should have payed more attention in class way back when. My last chemistry class was in 1977.

But I suppose TSP was the same then as it is now...

Jim

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Reply to
jim rozen

What you get is salt, NaCl. This salt residue will hide in every pore, crack, and crevice of the part, promoting corrosion. You get the same thing if you try to neutralize with lye or baking soda. So do *not* try to neutralize the HCl. Just rinse the part off with plenty of hot water (chlorides are soluble in hot water). The hotter the water, the better, because solubility increases with temperature, and the hot water will evaporate off the part faster, so the part doesn't stay wet long.

Note that the metal will be *extremely* clean at this point, and will flash rust if you don't immediately oil it or otherwise protect it from contact with oxygen. That's why the galvanizing guys normally do the HCl dip and rinse immediately before galvanizing.

Note too that you don't have to worry about the rinse water going down the drain. You need to use lots of it, and it will dilute any HCl it washes off the part to harmless levels.

Sure, it *is* fertilizer. If you only have a few gallons of the stuff, dumping it down the sewer isn't a problem either. The environmental concern was when *everyone* was doing it (laundry detergents with TSP), and the result was algae blooms downstream of the sewage treatment plant. But a few gallons is nothing.

For *these* chemicals, dilution is the solution to pollution. That's not true for some chemicals, or industrial quantities of most chemicals, but it is fine for disposing of the small amounts of acids and bases used around the home shop.

Gary

Reply to
Gary Coffman

Grant and Ed, You might want to check the label on the box to see just what you have. TSP is not easily procured in New York State. Yes it says TSP on the box, but the fine print where it lists the ingrediants says Sodium Carbonate. Sodium Carbonate is cheaper when bought as Sodium Carbonate.

Here in Washington State, the fine print says contains TSP and Sodium Carbonate. At least that was what the box at Lowes said. I have not checked at Home Depot and ACE.

Dan

Reply to
Dan Caster

We have both products here in NJ, Dan. The stuff I have is straight TSP.

Ed Huntress

Reply to
Ed Huntress

Gary has hit the galvanized nail on the head. Any standard neutralization of HCl will produce NaCl. Consequently, Gary's is right when advising thorough rinsing. I believe the culprit to accelerated rusting is the chloride ion. The only way to avoid this is to use a different acid, i.e. sulfuric acid, H2SO4. I don't know if this is good for cleaning steel or if it would cause problems with the ensuing galvanization.

John

Reply to
Me Mine

Yes, but the downside on this is, you also have Secuacus! :^)

Jim

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Reply to
jim rozen

But one never has to go there, nor to West New York, nor even to Perth Amboy. d8-)

As for dangerous chemicals, they're like Black-eyed Susans are in some other parts of the country. You can just gather them by the side of the road.

Ed Huntress

Reply to
Ed Huntress

I remember there was a lady who was running a operation in Perth Amboy, she had a contract to barge sewage sludge out beyond the limit. They caught her crew pumping the sludge onboard the barges, and at the same time pumping it overboard right at the dock! She was famous.

LOL.

Jim

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Reply to
jim rozen

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