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Old 04-12-2011, 11:08 AM   #1
Gumby73
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Default Muriatic acid to eat aluminum?

1973 Honda CB350

I had my cam bearing seize up on me due to an oiling problem. As a result, some aluminum is stuck to the cam. The cam looks reusable but I need to remove the aluminum first. A shop suggested soaking in muriatic acid to eat away the aluminum but cautioned that it could harm the cam as well. I'd like to avoid that, and I was wondering if anybody had any experience with this kind of thing.
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Old 06-02-2011, 05:17 AM   #2
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try using a wire brush on a bench grinder to remove the aluminum then go over the surface with emery cloth also make sure to check your bearing clearances when reinstalling
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Old 06-02-2011, 06:44 AM   #3
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muratic acid is hydrochloric acid with some dissolved iron making it yellow in color. It will react with metals, forming a salt and releasing hydrogen (all metal/acid reactions do this). muratic acid tends to dissolve aluminum quite rapidly, about 4 times faster than sulphuric acid (often the electrolyte in lead acid batteries). It will dissolve the cam slower but it may cause pitting. I would advise caution with that method, although it would work.

To see how quickly HCl+Al makes H2 gas and AlCl salt with an exothermic reaction in a confined space watch this video (2l bottle, muratic acid and aluminum foil)
+ YouTube Video
ERROR: If you can see this, then YouTube is down or you don't have Flash installed.
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Old 06-02-2011, 07:35 AM   #4
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Thanks for the advice. Most people I have spoken with about this have cautioned me the same. I have every intention of doing it outdoors and keeping myself protected with sleeve length rubber gloves and an apron. I am also planning on a "quick dip" method in which I will dip the cam in and remove it quickly to minimize cam surface exposure. I'm also considering diluting it maybe 50/50 with distilled water to further minimize the risk of pitting.

By the way that's an awesome video... except now I want to get some bottles and foil and give it a try myself.
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Old 06-02-2011, 01:32 PM   #5
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if you do that with the foil and bottle do not add the foil until you are ready. Do not use a bottle with a metal cap, plastic only. If you are unsure about how reactive the plastic might be with the acid do not mix until you are in a safe location. Remember things that go boom can have shrapnel which can put an eye out and splash acid all around the area. draino can also work.

The acid you would buy (probably at a pool supply store since muratic acid is used to clean pool tile) is not pure, it already has some water in it. You would need to read the label and see what concentration it already is, diluting it may make it too weak to eat off the metal buildup.

Additionally my hope is that you recall high school chemistry class and the safety procedures. Eye protection (face shield is better) and wear some disposable outer layers of clothes (lab smock if you have one as those are generally treated to make them more resistant). If the acid gets on you it can cause burns, blind you, or just eat through your clothes. Rubber gloves like for dish washing is also advised (although proper gloves would be better kitchen style are usually good enough). Remember what happens when you mix acids and bases, keep alkaline things away. blah blah blah
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Old 06-02-2011, 01:53 PM   #6
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Wanted to add that you may want to use windex to neutralize the acid. Strong acids and strong bases can cause a rapid reaction, however windex is a weak base (ammonia quite diluted). Windex is used by some gun owners whose rifles shoot corrosive ammo, it neutralizes the acidic salts that are in the residue after shooting. This prevents pitting of the barrel. To prevent pitting of the cam you may want to have some windex on hand and when you are going to stop for a while, or think you are done spraying that on and wiping it down multiple times can help to halt the corrosive effects of the acid. After the windex you will want to clean and care for the cam like normal.
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Old 06-03-2011, 08:44 AM   #7
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Thanks for the further safety advice. In all likelihood I will probably never do the exploding bottle thing- it's just one of those things that looks and sounds fun.

I already have the acid- bought it from Menards- I think it's intended for masonry/concrete applications but I'll have to look closer at the label.

Unfortunately I was never good enough at math to reach chemistry in high school, but everything you mentioned I have intentions of using. Just seems like common sense type of stuff, but we never know who may be reading this, right?

I wasn't aware that windex would neutralize it. I was just planning on having some baking soda handy.

Thanks again for all your advice.
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Old 06-03-2011, 04:55 PM   #8
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There is one thing I remember from HS Chem.

With a THICK Brooklyn accent, "Due as you auta, add acid to wata."

Mr C's voice will be with me always.
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Old 06-03-2011, 08:04 PM   #9
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Quote:
Originally Posted by Gumby73 View Post
I already have the acid- bought it from Menards- I think it's intended for masonry/concrete applications but I'll have to look closer at the label.
Most of the sales of muratic acid is to clean masonry, why I mentioned pool supply places to clean the tile around the pool.

Quote:
I wasn't aware that windex would neutralize it. I was just planning on having some baking soda handy.
When you mix an acid and a base you get a salt (not necessarily table salt though) and water. If you mix a strong acid and a strong base you get a more violent reaction. Windex is a fairly benign base due to the low concentration of ammonia. This is why it is used in gun cleaning when corrosive ammo is used (for example Mosin Nagants that fire 7.62x54R which are almost always corrosive). The acid will pit the metal barrel, which dramatically lowers accuracy.

In the case of your cam you are applying a stronger acid (based on concentration) and while it will more readily react with aluminum than the steel, it will react with it. As a result you will want to use it sparingly and when you are done use windex so it does not pit the cam. If you use a toothbrush or some other brush to try to brush off the aluminum as it dissolves watch for spatter. If your toothbrush is wet and you run your thumb across the bristles it will spray a mist of water, well the same holds if there is acid in the bristles and you brush the cam, it will spray. You can ruin clothes, harm skin, blind yourself, etc. Why gloves, smock (or other suitable clothing) and eye protection are essential. It can also spray onto others nearby, objects nearby you did not intend to be etched by the acid, etc.
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Old 06-04-2011, 12:24 AM   #10
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Old-fashioned Draino will eat away the aluminum, too. If you look in side, along with the white crystals, are aluminum flakes. They are there to keep the Draino from eating the copper drain pipes, because the aluminum reacts faster. I believe the same would be true for steel/iron.
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Old 06-04-2011, 02:06 AM   #11
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scroll up I said that draino works for the bottle bomb, which does the same reaction as the muratic acid (HCl). Liquid plumber/draino would be better than the crystals because its a gel that can be carefully applied with a q-tip. That actually may be a better way to go about this, had you not mentioned that I may not have thought of a q-tip and if no one else did and no one else mentioned it it may not have been offered as a suggestion

And yes Al will react faster than the steel or some other metals, zinc goes pretty quick as well. Here is a neat trick with left over acid. Take a new penny (newer than about 1966 when they became zinc core instead of solid copper) and nick the side to expose the zinc core. Drop it in a bit of acid so it is covered and let it sit. Eventually the core will be eaten out leaving the copper shell. It will look like a penny but be very light. You can also crush it easily in your fingers.

Remember when you mix an acid and a metal you will have hydrogen gas released and a salt form, in concentrations the hydrogen gas can be dangerous (it takes a considerable build up to actually become explosive, its about ratios hydrogen to oxygen). If you are doing small bits of metal particularly in a large room (or better a well ventilated one) the gas cant get in enough concentrations - its like charging a battery, same gas too.
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Old 06-04-2011, 12:25 PM   #12
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Quote:
Originally Posted by trixter View Post
Remember when you mix an acid and a metal you will have hydrogen gas released and a salt form, in concentrations the hydrogen gas can be dangerous (it takes a considerable build up to actually become explosive, its about ratios hydrogen to oxygen). If you are doing small bits of metal particularly in a large room (or better a well ventilated one) the gas cant get in enough concentrations - its like charging a battery, same gas too.
Which is why I would use sodium hydroxide, instead of hydrogen chloride.
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Old 06-05-2011, 12:12 AM   #13
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With muratic acid, get something to cover your nose and mouth. When i used it on our concrete floor, it burned like a mother when I got a wiff of it on accident.
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Old 06-23-2011, 12:01 PM   #14
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I just wanted to let everybody know that I used the acid procedure this morning... and now I will need to get fitted for a prosthetic hand in a few weeks.

Just kidding. It all went fine. I was nervous about it at first, in part because I rarely handle chemicals that toxic, but also because I obviously didn't want any pitting to occur. But I first tested it on some aluminum foil just to get a feel for the reaction time and once I knew about what to expect, it went rather well.

I used the quick dip method several times over. I'd dip it, let it work for a few minutes, dip it again, let it work, etc. All said and done it took me about 15-20 minutes to get all the stuck on aluminum off, and NO PITTING!

By the way trixter, thanks a lot for the windex tip- that came in quite handy. Every few dips I would use the windex to neutralize the acid on the shaft and clean it with a wad of paper towels just to see how it was progressing.

I have to go to bed now but tomorrow morning when I get home from work I will be able to polish it, finish putting the top end together, and then this weekend I will be able to get the motor reinstalled and hopefully...


Hehehehehe......
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Old 06-23-2011, 01:25 PM   #15
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Quote:
Originally Posted by Gumby73 View Post
I just wanted to let everybody know that I used the acid procedure this morning... and now I will need to get fitted for a prosthetic hand in a few weeks.
Well this is what I made, it may help ya http://www.0xdecafbad.com/category/Prosthesis


Quote:
By the way trixter, thanks a lot for the windex tip- that came in quite handy. Every few dips I would use the windex to neutralize the acid on the shaft and clean it with a wad of paper towels just to see how it was progressing.
I would like to say that is because I paid attention in school but the reality is a friend as a Mosin Nagant rifle which shoots corrosive ammo and he uses windex after going to the range to neutralize the acidic salts in the barrel to prevent pitting.
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