Coating Mg

[TrueBluePyro]

I'm about to buy some Mg and Im wanting to coat it with linseed oil. I dont really like the idea of Potassium Dichromate and I wouldnt need to use it as I wont be using any AP and when using linseed oil, the only thing it cant protect the Mg from is AP.

[Bonny]

I'm about to buy some Mg and Im wanting to coat it with linseed oil. I dont really like the idea of Potassium Dichromate and I wouldnt need to use it as I wont be using any AP and when using linseed oil, the only thing it cant protect the Mg from is AP.

 

I think you use 2-5% linseed oil (IIRC). Heat the Mg in a pan add the linseed oil and keep stirring to stop it from clumping. Allow to cool and run througha screen (again to break up the lumps). Spread it out on some newspaper and let it "dry" for a week or so to allow the linseed oil to plasticize.

[TrueBluePyro]

And how would you go about coating it with Potassium Dichromate, I hear it is a little easyer to coat the Mg and easyer to work with.

[Arthur]

Dissolve the dichromate in water and spoon the metal in! the colour of the dichromate should fade as the surface of the metal reacts and forms the passivating layer. Filter the metal out rinse and dry carefully. (You wouldn't be interested if it wasn't a flammable metal!)

[TrueBluePyro]

cool, I have read up on the passfire arcticle as well, but is it easyer to work with? once it has the dichromate on it, you would have to be careful not to touch and wear a mask when useing the Mg?

[Mumbles]

I am more a fan of the passfire method of coating, which comes directly from Shimizu (more or less). I'm not sure where the soaking in excess of room temp solution came about from, but it raises the problem of excess depleted dichromate hanging around.

 

Neither method makes the Mg any easier or difficult to deal with. You should be using a mask when dealing with these fine of chemicals anyway. I always wear gloves when working with dry powders as well, so coated or not, Mg gets treated the same by me.

[al93535]

To coat your magnesium properly and entirely I would advise the use of a solvent to thin the boiled linseed oil. 2% by weight of linseed oil will never fully coat all the mag without thinning it first. I would use lacquer thinner or some other suitable solvent. Acetone might work well but may dry too fast. Just make sure to completely coat the mix by gloved hands. I don't remember what solvent I used, I coated enough mag to last quite some time. I never heated my magnesium when coating it with linseed oil... I don't see the point. When the coated magnesium is set aside to dry spread it thin! Curing linseed oil is an exothermic reaction and too thick of a pile can spontaneously ignite! 1/2" thick layers are fine. Screen the coated product after several days to de-clump it, you will need to do it a few times.

 

The magnesium will need several days to two weeks to completely dry.

 

I would highly advise coating your magnesium, a little prevention has saved alot of trouble!!

 

I have treated magnesium with potassium dichromate with the method shimizu points out in his book. It has always prevented reactions with AP.

[QED4803]

Is there anything more definite in the literature regarding the use of linseed oil in coating Mg? I would prefer to use linseed oil over potassium dichromate simply to avoid the clean-up and disposal issues, but none of the literature at my disposal describes its use in any detail. There are several specific questions I would like to put to rest before committing a batch of Mg to this procedure, viz:

 

~How much oil? 2-5% is a pretty wide range.

 

~Is "boiled" linseed oil truly my best choice? It appears that "boiled", in modern parlance, actually means adulterated with various substances to promote faster polymerization. According to at least one source these adulterants may include chromium and other metal compounds. Might any of these additives cause me headaches (literally or figuratively) somewhere down the road?

 

~Thinning of linseed oil is traditionally done with mineral spirits--is this a good plan for my purposes?

 

~How concerned should I be about spontaneous combustion, and what precautions are appropriate in this regard? It is well known that rags soaked in linseed oil have caused numerous fires owing to the exothermic nature of the polymerizing process.

 

Thanks to all the contributors, from whom I've gleaned numerous bits of knowledge over the past few months,

Smitty

 

"Good judgement is the result of experience; experience is the result of bad judgement." source obscure

[dagabu]

I have been using Parlon to coat my Mg since Swede showed his preliminary results with it. I keep my Mg based comps outside in a steel container so if they do decomp, I will be fine but no problems so far.

[NightHawkInLight]

I have been using Parlon to coat my Mg since Swede showed his preliminary results with it. I keep my Mg based comps outside in a steel container so if they do decomp, I will be fine but no problems so far.

I'm interested, how does it preform? Does it do well with AP? Well enough to use water based binders perhaps?

[dagabu]

I'm interested, how does it preform? Does it do well with AP? Well enough to use water based binders perhaps?

 

I don't think I am prepared to tell anyone else to use Parlon to coat Mg but I do and I use it in water based comps.

[NightHawkInLight]

I don't think I am prepared to tell anyone else to use Parlon to coat Mg but I do and I use it in water based comps.

Sure. Well I can use my dichromate coated Mg in water based nitrate comps, but still not with water and AP. If you give it a shot be sure to post. Also any positive/negative effects in various compositions that you witness would be great to hear.

[Swede]

I agree... dagabu, AFAIK you are the first to actually formulate true comps with parlon-coated Mg. My tests were very basic but they did show a very definite protection, superior to dichromate, but ONLY in a simplistic aqueous attack by a mineral acid, HCl. Any results, positive or negative, that you get from the process, would be very valuable.

 

The other thought I had was that the coating process was very easy with coarse Mg, maybe 30 mesh, but I did not attempt it with a finer Mg. When the Mg is wetted with the non-polar solvent like MEK or acetone with parlon dissolved in it, it initially dried into clumps. When those clumps were broken up, and the drying completed, the Mg flowed nicely - but again, no tests were done with finer Mg.

[Twotails]

What about Saran? think it wold work at coating the Mg?

[Mumbles]

It could work. Let us know after you try it out.

[Twotails]

I'll try it tonight after i get back from shooting my shells. How much do you think, 2%-4% dry weight? or is that too much?

[dagabu]

I agree... dagabu, AFAIK you are the first to actually formulate true comps with parlon-coated Mg. My tests were very basic but they did show a very definite protection, superior to dichromate, but ONLY in a simplistic aqueous attack by a mineral acid, HCl. Any results, positive or negative, that you get from the process, would be very valuable.

 

The other thought I had was that the coating process was very easy with coarse Mg, maybe 30 mesh, but I did not attempt it with a finer Mg. When the Mg is wetted with the non-polar solvent like MEK or acetone with parlon dissolved in it, it initially dried into clumps. When those clumps were broken up, and the drying completed, the Mg flowed nicely - but again, no tests were done with finer Mg.

 

That drove me nuts! I couldn't find a way to resolve this at first and I was convinced that breaking the clumps up was going to strip the Parlon off on side or the other or so I feared. Turns out that there is no noticeable difference between separating (ARRRGGH) it when wet or waiting till dry and breaking them up.

 

Please, do not use Parlon with AP yet, I have no testing with this yet and I don't want anyone hurt.

Edited January 19, 2010 by dagabu

[NightHawkInLight]

Please, do not use Parlon with AP yet, I have no testing with this yet and I don't want anyone hurt.

Well obviously if I tried it for myself I would do my own testing.

[Twotails]

Im about to go try coating Mg with Saran, i'll report back with my findings.

[al93535]

~How much oil? 2-5% is a pretty wide range. 4% will work just fine!

 

~Is "boiled" linseed oil truly my best choice? Yes it is, its the only choice.

 

~Thinning of linseed oil is traditionally done with mineral spirits--is this a good plan for my purposes? An excellent choice!

 

~How concerned should I be about spontaneous combustion, and what precautions are appropriate in this regard? It is well known that rags soaked in linseed oil have caused numerous fires owing to the exothermic nature of the polymerizing process. Leave the trays of drying mg/oil in thin layers, less then 1/2" check it often and sift it often. I wouldn't be to concerned unless you have really large amounts in heaping piles!

 

Weigh the Mag to be coated. Weigh 4% of that out in Linseed oil. Thin the oil. I used about 7X the weight in volume of solvent. So 100 grams of Magnesium would be coated by 4 grams of linseed oil dissolved in 28 ml of solvent. Mix the oil and solvent well, and pour over the mag. Using gloved hands mix and knead the mg/oil until it is all fully coated. spread on pans to dry. It will take a long time to dry

 

 

As for coating Magnesium with saran: What available solvents do you have to dissolve the saran resin? Acetone doesn't do it... There are a few specialty solvents that will, but they are not available at the hardware store.

 

 

If you are coating MG for use with anything but AP use linseed oil. If you are coating MG for use with AP use dicromate!

 

from shimizu (which is how I do it except without heating the magnesium) Always works excellent:

 

Coating with potassium bichromate is carried out as follows:

50 grams of potassium bichromate is dissolved in 300cc of hot water.

1000 grams of magnesium powder is heated to about 100°C in an air oven

for one hour. It is placed in a large aluminium bowl and the hot solution

of potassium bichromate is added to it. It is quickly mixed stirring

by hand with gloves until the powder colours uniformly brown. Then the

powder is spread on a kraft paper and dried well in the sun. When dried.,

it is passed through a 30 mesh sieve. The dust must not be inhaled

because potassium bichromate is poisonous.

[Twotails]

I saw that a solvent for Saran is acetone, and that i do have. its already mixed(did it last night) Im trying it out later, seems to have coated the Mg, but i'll have to find that out in testing. Im bord, so it gives me somthing to do.

[Mumbles]

Did the saran actually dissolve? I was under the impression that it can be used as dillutant when combined with a true solvent or as a softener where it doesn't actually dissolve the saran.

[swervedriver]

I soaked my saran in acetone for 48 hours, it doesn't dissolve. After drying it out, it was a fine powder just as it was when I added acetone to it.

[Twotails]

It seemed to desolve, But it could just be that it seems that way. When the coated Mg is moved from one contaier to the next, There seems to be no powder left behind. So it may not be coating the mag, but im not sure. more tests are needed.

[Swede]

PVC may be another alternative and may form a barrier that is superior to parlon. It'd be best to use some tetrahydrofuran and MEK as solvents, which can be kind of expensive, but perhaps acetone and MEK can dissolve enough to make it workable.