Guys, I was all about home anodizing.  I went out and bought 98% sulfuric acid and made a tub of solution to annodize my 0% AR10 recievers I just finished.  But after being so gung-ho about it I now have a local company lined up to do hardcote for me.  So I had invisioned setting up and annodizing a bunch of parts over a long time but now I could care less.

So here I sit with this kitty litter tray of acid in my work room.  I have diluted the acid to 30% when I started and I would guess I made up about 2 or 3 gallons.  

How the hell to get rid of this crap?  I can't just dump it so I figured I would nuetralize first.  I bought a 4lb box of baking soda at Walmart but it didn't even come close.  So far I have dumped 12 lbs of baking soda in the tray and it still reacts like crazy!  How much is this going to take?  Also when I do finally nuetralize, I am left with water and salt I think .  So does this mean I can dump this crap or is it still harmfull to the environment?  I am going to dig out my old chemistry book.  

Any ideas?

You are probably going to have keep diluting/neutralising until the Ph falls within an acceptable range. If you have any heavy metals in the solution dumping it is probably out of the question. I'm a little out of touch , but as a suggestion call around from the yellow pages to some metal pre-treatment/metal finishing/anodisers and speak to the technical manager or chemist I have found these type of people are pretty good guys . Perhaps they'll allow you to mix it in with their waste for treatment and disposal.  Get their advice on transporting it too.  Good luck,let us know how you get on.

LOL...98%...you ain't got nowhere near enough baking soda...I hope you didn't buy much acid.

In my experience, it takes about 1 lb of baking soda per quart of 5% H2SO4..so I would estimate it would take about 80lbs per gallon of 98% stuff.

The easiest way is to do it in your backyard. Take a 5 gallon bucket,  and fill it with 4 gallons of water, then add 1 CUP of acid. That should dilute it to about  1% concentration. At this point you can flush it down the drain. If you have problems with clogged drains, dump the diluted acid down those drains. Depending on how much you bought, it may take all day. When you are all done, flush a few gallons of water down each drain you used, then follow with couple pounds of baking soda + water to make sure anything left in the plumbing is neutralized.

This is probably more cautious than required as sulfuric acid is usually used as a drain cleaner and can be bought at home depot type stores, but if you have old pipes, its that safest method as it will eat thru copper, steel, cast iron if left in contact for a long period of time. It won't harm plastic pipes though.  

The good news is that by the time you're done, your house plumbing will be all nice and clean.

Next time, if you get the urge to anodize, use battery acid. Its only 19.35% by volume and probably much cheaper than the 98% reagent grade.

Good luck...and be careful. Sulfuric is nasty stuff!

0% receivers? I hope you don't mean that you anodized before completing the machining. Anodize is a ceramic (alumina) enormously hard and brittle. Even solid carbide tools won't cut alumina; they just shatter it and break it off in chunks, or the tools breaks

Even from what little you said, I have no doubt that your anodizing attempt(s) were a dismal failure. For one, the electrolyte (acid mix) is supposed to be 5% - 10% (by volume) depending on the anodizing process used. Let's not even discuss the rest. For you, having it done professionally is the best choice.

Diluting the acid 25 to 50:1 with water is safe if you have a city sewer system. Neutralizing it with baking soda is not a bad idea, you don't need to neutralize it completely (no fizzing). Neutralizing may be necessary if you have a septic system, I don't know much about septic systems.

I have only used a few mayonase jars full of the sulfuric.  It is diluted to about 30% in the tub I have.  I thought drain cleaners were strong bases, like Lye?  I am on a septic system so anything I pour down the drain is going to end up in my yard


Anyway I have added about 14 lbs of baking soda so far.  The rest of the acid is still virign and in the original container so that I am going to drive back into town.  The place I bought it from will accept it.

Call your local sanitation department.  They usually have a hazmat collection for household waste, to prevent it from getting into the landfill.  

Quoted: 0% receivers? I hope you don't mean that you anodized before completing the machining. Anodize is a ceramic (alumina) enormously hard and brittle. Even solid carbide tools won't cut alumina; they just shatter it and break it off in chunks, or the tools breaks Even from what little you said, I have no doubt that your anodizing attempt(s) were a dismal failure. For one, the electrolyte (acid mix) is supposed to be 5% - 10% (by volume) depending on the anodizing process used. Let's not even discuss the rest. For you, having it done professionally is the best choice.

LOL the recievers are done, I know I look like a retard with my current problem but I'm not that dumb.  Besides from what I have read home anodizing really doesn't produce the same results as hardcote anodize, I was more interested in dying.  

Based on the tutorial I have read on the web, 15- 30% is what most guys use, and I am somewhere between 25-30%.  The 98% is simply how it came.  

Thanks!

This is the main source I was using:

www.focuser.com/atm/anodize/anodize.html

Here are my recievers:

www.ar15.com/forums/topic.html?b=3&f=4&t=198144

Use caustic soda, it's VERY basic.  My brother was putting some in the chemical feeder for our water system when he was a teenager.  Then he scratched his balls.  hock.gif

It started burning through his skin, so he jumped in the shower.  Of course, I knew that it was a basic substance, and he needed something acidic to counteract it, so I gave him some vinegar to put on it.    It did neutralize it, but boy did he scream!!

Check if your city or county has a hazardous waste disposal facility.    I had to get rid of a couple gallons of  battery acid when cleaning up the garage, and they took it  w/o any reservations.     You can get a cheap plastic fuel can to transport the stuff in - I did that and just left the whole thing.

Find some dead bodies.  I hear that acid does a wonder on them.

Counterstrike,

I looked at your receivers, very nice work indeed.

Some clarification abput Type III (hardcoat). If your anodizer can't provide (or you don't ask) for his certification of a Type III coating, you probably won't have a Type III layer. It will be "Type II 1/2", this is regular Type II (what you attempted to do) grown to Type III thickness (1-3 mils). Will this make any practical difference on your receivers? No it won't, it takes a testing lab to tell the difference, you or I couldn't tell. You will pay more for Type III, be sure that's what you get.

You are right about a difference in quality between "professional" and "amateur" anodizing. When the "amateur" has taken the time to understand everything, and gets the process and equipment right, he consistantly produces better, more uniform results than the professional. Why? because its much easier to control all the parameters in small scale than in large. I'm not kidding.

(edited to add)

The standard "professional" electrolyte concentration is 9.4%. This is used by the majority of commercial anodizers throughout the world. I know Ron Neuman, on this point I don't agree with him. Electrolyte that strong makes for dissolution problems that could have been avoided. Its possible this is what did you in, but there are also many other pitfalls for the misinformed.

Quoted: I have only used a few mayonase jars full of the sulfuric.  It is diluted to about 30% in the tub I have.  I thought drain cleaners were strong bases, like Lye?  I am on a septic system so anything I pour down the drain is going to end up in my yard Anyway I have added about 14 lbs of baking soda so far.  The rest of the acid is still virign and in the original container so that I am going to drive back into town.  The place I bought it from will accept it.

Good thing you didn't try to anodize at 30%. Even professionals only use about 10% concentrations.
Most home use drain cleaners are bases, however, there are cleaners labelled "professional strength" that are in fact diluted sulfuric. You can find them at Home Depot, etc. You can usually tell as not only are they in a thick plastic bottle, but they are also wrapped in a thick, sealed, plastic bag.

I'm glad they are taking it back. It makes the whole situation go away, which is the easiest way to handle it. As for the stuff in the tub, just keep diluting it and don't be afraid to dump it down the drain once you get it to the point that it won't eat thru the pipes.  Diluted sulfuric isn't considered a hazardous substance in the amounts you are dealing with.

As for the hardcoat stuff, fibergeek explained most of it. Get a explanation of what your anodizer calls hardcoat. There is no real way to tell, but here are some definitions for you;

Type - II:   Less than 25.4 microns thick. Easy to dye.

Type - III:  Greater than 25.4 microns thick. Difficult to dye without using hazardous anodizing and dyeing additives. A higher density of anodizing cells which can only be measured using an electron microscope or by chemically removing the coating and determining the weight of the coating per sq. inch.

Hardcoat: In the anodizing industry, hardcoat use to mean it was Type-III, but it seems to have taken on a new  meaning over the years.  The new definition means anything more then 25.4 microns thick yet is easy to dye. It is not a true Type-III, but in fact just a thicker Type-II coat. I'm willing to bet that if your lower is going to be dyed, it will be a thick type-II coat rather than a true Type-III, and if he's honest the coating will actually be thicker than 25.4 microns. But, how are you going to tell whether it is 10 microns thick or 26 microns thick? Even the AR manufacturers have adopted this definition rather incurring the expense involved in true Type-III anodizing.

Out of curiosity, how much is he charging you?

The price is $100 per batch.  I provided the total surface area of all the recievers I had and the overall dimensions and apparently they are below the minimum so I just get the minimum price of $100.

The quote I recieved was $60 for black anodize, $100 for black hardcote anodize.  There were no specifics given as to thicknesses nor hardness ratings.  To be honest I am not totally concerned.  The recievers came out really nice and I just want to finish accordingly.  If they are not to 'mil-spec' I could care less, I just don't want to spray paint them at this point, or anodize at home and have them come out purple.

That sounds about right. If you do all the prep work, it doesn't matter how many you do at once, the cost is the same. The limiting factor is the power supply or rectifier and the size of the tank. BTW, the risk of a purple color is the same for professional anodizers as it is for home anodizers.  Ask Bushmaster!