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View Full Version : The Home Shop... Chemist?! (Warning: Metalworking Content)



Liger Zero
10-01-2010, 03:01 PM
Ok long story short... I need to rust some ductile iron and I need it VERY RUSTY and I need it VERY RUSTY by Monday.

I'm talking pitted flaky OMG RUST. Not pitiful red dusty surface rust.

Normally I use a detergent, hot steam, and time to rust them to perfection... I have detergent and plenty of hot steam but I'm all out of time.

Now, I have the following chemicals:

Epsom Salt
Rock Salt
Table Salt
Powdered Citric Acid
Baking Soda
Muratic Acid
Battery Acid
Ammonia
Bleach
Pool Chlorine
Simple Green
Pine Sol
Ivory Soap
Laundry Detergent
Oxy Clean


These I have in large quantities or I can get large quantities over the weekend.

Is there a way to accelerate the rusting process in a controlled manner using one or more of these chemicals? Assume I have large tanks, safety gear, proper ventilation, and a environmentally safe disposal process.

jep24601
10-01-2010, 03:10 PM
The electrolytic process will rust faster than anything. It is the same process as for rust removal but you reverse the anode and cathode so that you create rust instead of removing it.

Most of us use washing soda solution for the electrolyte. Not sure which of your chemicals might work best otherwise.

Liger Zero
10-01-2010, 03:12 PM
Dangerous chemicals AND high voltage, man my wife is going to cuss up a storm over this one. :D

I'll keep this on the back burner so to speak. ;)

dewat
10-01-2010, 03:44 PM
I like the reverse electrolytic process. I just rusted up a couple of pieces of CRS to test out a rust bluing process, I let the pieces etch in muriatic acid for 10 min. then hung them in a plastic garbage can with water in the bottom and the lid on. In 48hrs they were pretty rusty. And here in AZ the humidity is only 10% or so.
Washing soda is what is most recommended I couldn't find any so I use lye, but I've read you can use baking soda.

jep24601
10-01-2010, 03:55 PM
Dangerous chemicals AND high voltage, man my wife is going to cuss up a storm over this one. :D

I'll keep this on the back burner so to speak. ;)

Actually washing soda is pretty harmless (It is intended to put the stuff in with your washing after all) and the voltage will be plenty at 12v DC (I use a battery charger).

You will be really rusty in only a few hours.

Liger Zero
10-01-2010, 03:58 PM
You will be really rusty in only a few hours.

Ah so you heard about my attempt to play the piano last night... :o

Seriously though...

"only" 12 volts from a battery charger? I think that's do-able. I'll see what I can set up tomorrow.

MichaelP
10-01-2010, 03:58 PM
LZ, if it's not a classified information, what exactly are you involved in with this OMG RUST? The only things that come to my criminal mind are those connected to insurance or collector's fraud. Art, of course, will be a lame excuse, so don't even try. :D

john hobdeclipe
10-01-2010, 03:59 PM
Dangerous chemicals AND high voltage

Neither.

Use a 12 volt manual battery charger and washing soda (sodium carbonate.) If you can't find washing soda, go to a big box store and look at the swimming pool chemicals. Don't remember which, but one of them that is used to adjust the ph is 98% sodium carbonate. Don't waste your time measuring out so much per gallon, just pour it in and stir it up until the water feels soapy or kinda of slick-like.

Use a big cathode...the bigger it is the more amps will flow and the faster the reaction will be. If it's too big and the breaker on your battery charger trips just pull some of it out of the water.

It shouldn't take more than a few hours until the anode (positive terminal) starts to become a pitted, rusty mess.

The rig need not be fancy...here is one that I use:

http://www.auldooly.com/imagehost/MVC-908F.JPG

bob_s
10-01-2010, 04:08 PM
I'd just use a combination of battery acid and ferric chloride, it's called artificial sweat, and it'll corrode just about anything ...

ckelloug
10-01-2010, 04:09 PM
Muriatic acid will leave a thin but completely red film of rust as the surface dries. Nasty stuff.

Liger Zero
10-01-2010, 04:10 PM
LZ, if it's not a classified information, what exactly are you involved in with this OMG RUST? The only things that come to my criminal mind are those connected to insurance or collector's fraud. Art, of course, will be a lame excuse, so don't even try. :D


:D

The insulator product we manufacture has two metal hardware fittings on the end. The outside of the hardware has a special "value added" protective coating, the inside is not coated.

The insulator rod fits into this piece of hardware, and through a top-secret process involving deep dark magics, mystical forces and science the rod becomes one with the metal fitting in such a way that a tactical nuclear strike is required to remove it.

The rust and the pitting are an essential part of this process. Pitting by itself doesn't work... and rust by itself doesn't work.


Yes I am being silly but we are treading on "trade secret" here, I can't explain the bonding process because that gives us a leg up over our rivals down the road.

gary350
10-01-2010, 04:14 PM
Muriatic acid will do what you want.

Muriatic acid will clean rust off of steel if you dip it for a couple minutes then wash it with water. But if you put steel in Muriatic acid and leave it for about a week it will rust really bad.

Liger Zero
10-01-2010, 04:18 PM
I don't have a week, I need 2,000 pieces by Monday.

Normally I would dip them in a detergent solution, then put them in a steam-washer for several hours, then put them on racks to air.

Normally it takes about a week to process a batch to perfection.

Right now, machinery is being located from Over There to Over Here, and wouldn't you know it I got a HUGE blanket order from "#1 Major Customer" today.

lynnl
10-01-2010, 06:28 PM
The reverse electrolysis will certainly give a nice deep coating of rust, but I'm not so sure about the pitting. Or at least what I think of as pitting.

I think you'll just get an even rust layer on it, over a span of just a day or so, without much pitting present.
But I may be wrong. It's worth a try I guess.

I'd try several different recipes. Maybe some acid dunks or soaks, followed later by the electrolysis.

The 5 or 6 times I've done the electrolysis thing, I've used rebar as the sacrificial anode, or maybe that's the cathode. (I always have to refer back to the instructions.) And I've never noticed much in the way of pitting on that rebar, even after 2 or 3 days.

Liger Zero
10-01-2010, 07:20 PM
I don't have many to spare for test pieces... I was told by someone else that droppering dilute acid into the part then letting it sit overnight will cause the pitting I need... and the electroshockenfumenburnum (:D) process will rust the hell out of 'em.

Someone is coming over tomorrow who knows how to do electrolysis for rust removal. He said he can set me up and get me running.

MichaelP
10-01-2010, 07:55 PM
But you'll have to share his recipe and the result with us this time!

The Artful Bodger
10-01-2010, 08:03 PM
Just leave 'em in my w'shop and they will be rusty in no time at all!:D

Evan
10-01-2010, 08:34 PM
Do this outside well away from the shop and place a fan near the shop to blow the fumes away from the door. Put the parts in or on a wire basket or similar arrayed over an aluminum disposable turkey pan. Put in a small quantity of battery acid and heat it just enough to make it fume slightly. A good old trouble light under the pan should do. It works best if the parts are cold.

Battery acid won't eat the aluminum but it will corrode the steel overnight. If you want it even faster use a bottle of cold bluing solution instead of the acid.

jkopel
10-01-2010, 09:02 PM
Battery acid (aka sulphuric acid) dissolves aluminum just fine.
2Al(s) + 3H2SO4(aq) -> Al2(SO4)3(aq) + 3H2(g)

Muriatic (aka Hydrochloric Acid) is the better choice for causing rust.
Clean the parts of any grease or oil, and hang them in a plastic bucket with a lid. Spray a mist of water on them and then pour a little muriatic on the bottom of the bucket. Cover it and wait a while, they will rust like crazy. Be damn careful not to breath in the fumes when you open the lid.

Evan
10-02-2010, 12:44 AM
Sorry, but battery acid does not significantly affect aluminum. I do anodizing in aluminum pans. You can leave a piece of aluminum in H2SO4 for days with no particular effect.

http://metalshopborealis.ca/pics/ano1.jpg

snowman
10-02-2010, 07:11 AM
Neither.

Use a 12 volt manual battery charger and washing soda (sodium carbonate.) If you can't find washing soda, go to a big box store and look at the swimming pool chemicals. Don't remember which, but one of them that is used to adjust the ph is 98% sodium carbonate. Don't waste your time measuring out so much per gallon, just pour it in and stir it up until the water feels soapy or kinda of slick-like.

Use a big cathode...the bigger it is the more amps will flow and the faster the reaction will be. If it's too big and the breaker on your battery charger trips just pull some of it out of the water.

It shouldn't take more than a few hours until the anode (positive terminal) starts to become a pitted, rusty mess.

The rig need not be fancy...here is one that I use:

http://www.auldooly.com/imagehost/MVC-908F.JPG

You have a rig that is always set up?

man...my wife thinks I'm bad.

wierdscience
10-02-2010, 08:23 AM
http://metalshopborealis.ca/pics/ano1.jpg

Evan,you had better make that more professional looking,it looks too much like a Meth lab:D :D

gary350
10-02-2010, 09:44 AM
Mix about 1/2 cup of salt per gallon of water and use a 12 volt car battery. It has been several years since I have done this I can't remember if the parts are connected to positive or negative on the battery. You can get some pretty healty rust in an hour.

When I mentioned muratic acid for a week that will give you rust like an old civil war item that had been laying out in the weather for 150 years. If you need less serious rust muratic acid might do what you want.

Liger Zero
10-02-2010, 10:34 AM
We have a rig set up right now... it consists of an old hot-water parts washer filled with oxy-clean and salt.

When we tried the electro-whatever process it destroyed the plating on the outside as well.

The parts are rated against constant salt-fog contact under electric load... well the plated area is, the inside bore that I am trying to rust isn't. :)

SO far the hot water solution is working.

Ram
10-02-2010, 09:50 PM
What is it that your trying to rust up and deliver?

Weston Bye
10-03-2010, 06:43 AM
We have a rig set up right now... it consists of an old hot-water parts washer filled with oxy-clean and salt.

When we tried the electro-whatever process it destroyed the plating on the outside as well.

The parts are rated against constant salt-fog contact under electric load... well the plated area is, the inside bore that I am trying to rust isn't. :)

SO far the hot water solution is working.

So, is your process going to be repeatable? When the solution saturates the part-to-part variability will increase. You don't want to add value by overmolding an insufficiently rusted part. Have you or the customer established criteria for what is acceptable adhesion?

Maybe I'm being overcritical and TLAR* is sufficient for the part.

* That Looks About Right

Liger Zero
10-03-2010, 02:19 PM
Doesn't need to be repeatable, this is a "one time operation."

Normally our "repeatable" process consists of steaming the part in a chamber for two day, then letting them air-dry for two days. Normally this nets us "more than enough."

However, the steam chamber is dismantled and in transit from site B to site A. It will be set up and reinspected by the end of this week.

We chose this week because we had a lul in the orders. AS SOON AS they loaded the boiler on the back of the truck our biggest customer dropped a huge-ass order on us, they want 2,000 released VERY soon.

Talked to them about it, told them this sub-lot was going to be processed differently.

As long as they pass the in-process pull test and the post-process proof test they are considered good parts. The customer told us by email that so long as they pass the in-process test they don't care how we process them.

In process involves a 10 second pull to maximum in-service capacity, proof-test pulls them at twice maximum capacity and holds it there for a specific period of time.


By the way we are done now. Finished up at two am yesterday. :)

vincemulhollon
10-03-2010, 03:53 PM
Sorry, but battery acid does not significantly affect aluminum. I do anodizing in aluminum pans. You can leave a piece of aluminum in H2SO4 for days with no particular effect.

Aluminum oxidizes pretty quickly in air (lets call it instantly)

The oxide layer is quite impervious to most acid solutions, and soluble in alkaline solutions. Except for chlorine ions. So aluminum will dissolve slowly in hydrochloric and seawater, although not nearly as fast as in a hydroxide (basic) solution. My advice is not to store your aluminum in a bucket of hydrochloric, or try to do anodization using HCl because the store was out of sulfuric.

Hence the "old trick" of dissolving the remains of a steel tap out of an aluminum block using nitric acid. I've done it. HNO3 is expensive, but cheaper than an otherwise usable aluminum block.

If you scrape away the oxide layer while in that acidic solution, it'll dissolve nicely, an aluminum bushing or pivot would probably not live long underwater.

john hobdeclipe
10-05-2010, 10:02 AM
What method did you finally use for this project? Did it work? Did you get all of the pieces process on time?


You have a rig that is always set up?

man...my wife thinks I'm bad.

Hah! Chances are there was one of her cast iron frypans in the tank when I took the picture. She has bought several that were coated in thick layers of black grunge, paid only a few dollars for them, knowing that after 3 or 4 days in the tank they'll come back to her looking like new.

The Fixer
10-05-2010, 10:46 AM
John, that thick coating of black grunge is what they're supposed to have, it takes years to get them seasoned just right like that!!!

john hobdeclipe
10-05-2010, 11:50 AM
John, that thick coating of black grunge is what they're supposed to have, it takes years to get them seasoned just right like that!!!

Not when it's so thick that it falls off into the food. Besides, we don't trust the previous owner's grunge, we'd rather start off fresh and build up our own.

Liger Zero
10-05-2010, 04:36 PM
Not when it's so thick that it falls off into the food. Besides, we don't trust the previous owner's grunge, we'd rather start off fresh and build up our own.

Seconded. Used grunge is kind of sketchy.