chemistry question



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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Harold & Susan Vordos says...> I also suspect that simply rinsing the parts well, and

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
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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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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

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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
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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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On Fri, 31 Oct 2003 14:17:45 -0800, "Harold & Susan Vordos"
......and in reply I say!:

Producing a salt solution on the metal = rust????
****************************************************************************************** Until I do the other one,this one means nothing Nick White --- HEAD:Hertz Music
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wrote something

me a

dilute
I keep hearing that same response, but how much salt would be in question? One would have rinsed the parts in clear water, then in a solution of sodium hydroxide. When the items in question are introduced to the lye solution the amount of HCL remaining on the parts should be down to next to nothing, and would most likely already have been neutralized by the iron itself. If you've not put any steel in HCL, perhaps you should do so to understand the speed at which it reacts, especially if heated.
Please read the post by Koz, which is in keeping with my personal experiences as well. I have no argument with the theory of salt being a by-product, but one might consider the reality of the situation at hand. In this instance, the part(s) would be protected by the residual lye. It would be highly unlikely that any salt would have been formed.
Harold
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Harold & Susan Vordos wrote:

My PERSONAL EXPERIENCE is this: I found a charge-driving nail gun at the dump. Nice, but badly rusted. I took it all apart and put it in HCl. I then neutralized with lye (or maybe TSP). I rinsed really well, oiled it, and reassembled. I couple of days later I noticed quite a bit of rust. "Dang!", I thought, "I guess that I didn't neutralize well enough." I repeated the entire process and was _really_ careful about neutralizing. It rusted again, badly.
Bob
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On Sat, 1 Nov 2003 18:17:53 -0800, "Harold & Susan Vordos"
......and in reply I say!:

But if you have removed the HCl to the point where the salt will not matter, what is the point of "neutralising" it with the lye?
Smart-sounding question, but genuine. I have always used simple rinsing and then oil (WD40 or whatever) if needed rather than NaCl, because of the salt argument.
_Does_ the lye protect the steel in any way?

I have done it. Yes it rusts anyway if left.

Actually burying the steel in lye, as those conveyors apparently are, is quite different from having dipped them for a short while and then left them out to air.

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wrote:

I used Brownell's water displacing oil after rinsing when hot bluing firearms, which I haven't done in decades. The bluing solution was a hellish mix of caustic, sodium nitrite, and sodium nitrate, kept at 295 deg F by back-adding water (very carefully). Very nasty. The hot rinse was to remove the caustic (lye), etc. In theory, the oil displaced the water to prevent rusting. Bluing is a form of oxide which is relatively stable. Without a good rinse and oil, it'll still rust.
Pete Keillor

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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
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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

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Now you folks have me confused. We do metal conveyors for the potato industry. In days gone by, potatoes were peeled by soaking them in a very strong solution of caustic lye. This would dissolve the skins onto a slimy mess that could be washed off, leaving an effectively peeled spud (similar was done on peaches also). The practice has mostly been replaced by steam peelers due to waste disposal problems.
The point is, the carbon steel conveyors and frames of these systems lasted FOREVER. Even when steam cleaned, neutralized, etc, they never rusted. The caustic acts as a protectant of some sort and prevents corrosion rathern than causing corrosion as stated (on mild steel). The slimyness of the lye acted as a lubricant also so the wear was reduced. A conveyor just upstream, or just downstream (after the wash) might last a year but the conveyors in the lye...I never even remember replacing one. Most plants still have these machines for back-up...just washed and sitting. No rust still.
So what's the real story here? The statements seem to be conflicting with real-world experience.
Koz
Me Mine wrote:

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Koz wrote:

Actually, what was stated was that using a sodium caustic to neutralize hydrochloric acid would leave salt which would lead to corrosion. Also, just using HCl and rinsing it will leave a surface so clean that rust will begin immediately.
Bob
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wrote:

What we said was that using caustic soda, or baking soda, or any other alkali metal base to *neutralize* HCl remaining on the steel from an acid dip produces a salt (in this case NaCl, table salt). Unless the water is very hot, some of that salt residue will settle in any pores, cracks, threads, or other feature of the part. *That* will promote corrosion of the steel.
Obviously, if there is no HCl present, for example your potato conveyor, adding caustic to the water does not produce salt, and thus doesn't leave a residue on the steel which promotes corrosion.
In combination with the starch in the potatos, caustic *should* produce a carbonate scale on the metal which will in fact offer some protection from rusting. But scale is what the original poster is trying to remove, he wants bright metal ready for galvanizing. So caustic is not advised.
Gary
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Dang...long day and the HCL thing didn't sink in. Spud plants usually neutralize with sulphuric or similar during clean-up. BTW, no starch build-up to be seen on these units. Funny to see em brand new and painted by the fabricator...paint lasts about 15 minutes :)
Koz
Gary Coffman wrote:

--------------040104070408060100080100 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta http-equiv="Content-Type" content="text/html;charset=ISO-8859-1"> <title></title> </head> <body> Dang...long day and the HCL thing didn't sink in. &nbsp;Spud plants usually neutralize with sulphuric or similar during clean-up. &nbsp;BTW, no starch build-up to be seen on these units. &nbsp; Funny to see em brand new and painted by the fabricator...paint lasts about 15 minutes :)<br> <br> Koz<br> <br> Gary Coffman wrote:<br> <blockquote type="cite" cite=" snipped-for-privacy@4ax.com"> <pre wrap="">On Sat, 01 Nov 2003 11:29:23 -0800, Koz <a class="moz-txt-link-rfc2396E" href="mailto:kmiller@*dontspamme*metalbelt.com">&lt;kmiller@*dontspamme*metalbelt.com&gt;</a> wrote: </pre> <blockquote type="cite"> <pre wrap="">The caustic acts as a protectant of some sort and prevents corrosion rathern than causing corrosion as stated (on mild steel). </pre> </blockquote> <pre wrap=""><!----> What we said was that using caustic soda, or baking soda, or any other alkali metal base to *neutralize* HCl remaining on the steel from an acid dip produces a salt (in this case NaCl, table salt). Unless the water is very hot, some of that salt residue will settle in any pores, cracks, threads, or other feature of the part. *That* will promote corrosion of the steel.
Obviously, if there is no HCl present, for example your potato conveyor, adding caustic to the water does not produce salt, and thus doesn't leave a residue on the steel which promotes corrosion.
In combination with the starch in the potatos, caustic *should* produce a carbonate scale on the metal which will in fact offer some protection from rusting. But scale is what the original poster is trying to remove, he wants bright metal ready for galvanizing. So caustic is not advised.
Gary </pre> </blockquote> <br> </body> </html>
--------------040104070408060100080100--
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I think the standard, visceral demonstration for this is the one typically done in a beginning chemistry class. The instructor demonstrates some NaOH solution, how it will be terribly causting and then the same with some concentrated hydrochloric acid, again a piece of metal or whatnot dropped in the beaker,
Then you mix the correct proportions and the result is then imbibied in front of the audience. Salt water, see?
Almost as good as the milk carton full of oxy hydrogen mix from electrosis of water...
Jim
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I suspect the plating process won't worry if the part is wet with a little HCL on it - I suspect there is HCL in the plating and if not, the zinc will become zinc chloride in short time. And then the Hydrogen bubbles off in gas form.
Martin
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I suspect dipping anything wet into molten zinc would get a bit exciting. We are talking about parts that will be hot dip galvanized, not plated.
Gary
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