64 replies to this topic

[Frozentech]

i've heard of magnesium powder igniting when the media was dropped on it.

don't know why, but it gives you nasty burns. open the jar regularly, and if the jar is very warm, take great care.

Yeah, that was Bob Forward from rec.pyrotechnics who had that little accident, must be about 5 months ago now ?

[portfire]

OK.I was at a local hardware store today and noticed they had Linseed oil. 500ml for £2.50. Now I was going to get a few bottles but, they were two types..raw and boiled, so me been a tightass, i didn't get any and thought i check which one was more suited to the hobby? I'm guessing raw

Dean

[Arthur Brown]

Milling metals is usually helped by the addition of about 3% stearic acid It's a hard wax. (the binder in Polo Mints I think) Adding more lubricates the metal so well that the balls slide and the milling action ceases.

[digger]

OK.I was at a local hardware store today and noticed they had Linseed oil. 500ml for £2.50. Now I was going to get a few bottles but, they were two types..raw and boiled, so me been a tightass, i didn't get any and thought i check which one was more suited to the hobby? I'm guessing raw

Dean

Working in the refining industry, I would imagine the boiled will have been through a deodoriser (type of high temperature steam distillation). This means that it will have a lower FFA content (free fatty acid) amongst other things. Hence it will have a lower acid value (you can't measure ph on an oil).

So to cut a long story short I would lean towards the "boiled" as it will be purer and less corrosive.

[digger]

Milling metals is usually helped by the addition of about 3% stearic acid It's a hard wax. (the binder in Polo Mints I think) Adding more lubricates the metal so well that the balls slide and the milling action ceases.

Hey we refine stearic acid too (palm oil fractionation, then waste from producing monoglyceride emulsifiers)

Edited by digger, 12 April 2008 - 07:50 PM.

[portfire]

Milling metals is usually helped by the addition of about 3% stearic acid It's a hard wax. (the binder in Polo Mints I think) Adding more lubricates the metal so well that the balls slide and the milling action ceases.

Sorry arthur, my question was aimed at coating Mg...Which would be the best choice ?

[digger]

Sorry arthur, my question was aimed at coating Mg...Which would be the best choice ?

boiled as above

[portfire]

boiled as above

Missed that Thanx pal

[MDH]

I have always been curious as to why one does not simply make their own drum with a hole on one end covered by a piece of cloth in order to prevent the formation of oxides.

[digger]

I have always been curious as to why one does not simply make their own drum with a hole on one end covered by a piece of cloth in order to prevent the formation of oxides.

?

[portfire]

?

^^ What he said ^^ ????????

Edited by portfire, 12 April 2008 - 09:36 PM.

[portfire]

If it helps, the raw oil was clearer than the boiled. I would have thought the raw oil was the purist one of the two. As you have said digger, the boiling process would remove impurities, but wouldn't that make it clearer? or am I wrong ?

At £5 per liter it beats any price I've seen online, so I want to grap it while I can .

Dean

[digger]

If it helps, the raw oil was clearer than the boiled. I would have thought the raw oil was the purist one of the two. As you have said digger, the boiling process would remove impurities, but wouldn't that make it clearer? or am I wrong ?

At £5 per liter it beats any price I've seen online, so I want to grap it while I can .

Dean

Yes you are right it should make it clearer if was deodorised. I will check my reference books, however I have had a bit of a think and I would imagine that both the raw and the boiled are deodorised.

As I am sure you are aware Linseed oils are drying oils, where the oil undergoes an auto oxidation/polymerisation reaction which causes the oil to change and produce a hard film. So after a bit more thought and less beer (universal memory destroyer).

After doing a bit of reading the boiled may contain petrochemicals and metals to speed up the oxidation/polymerisation (this is not a product we produce as it is considered a non edible oil).

So in short the boiled will dry faster but may contain other additives, whereas the raw will be pure linseed oil I would therefore imagine that either will do if you are going to be boiling the magnesium in it (outside), but the boiled will dry more quickly so long as you are not concerned with the presence of petrochem solvents and possible metal drying catalysts (copper and iron speed up the polymerisation/oxidation of oil significantly).

Sorry for the slightly misleading previous post, hopefully there is enough info here to make a choice.

[Arthur Brown]

Going back to the milling metals posts! If you mill a reactive metal it will form and oxide on the newly exposed surface, if there is oxygen present, unless the new surface is already coated.

SO. Mill aluminium or magnesium or magnalium and you expose fresh surfaces as you mill. If you add about 3% stearic acid then you have enough wax in the mix to cover the surfaces as formed. Add too much and the wax lubricates the powder and media so that milling ceases.

Milling reactive metals dry is done in an inert atmosphere - nitrogen or argon mainly. but the highly active powder can take fire spontaneously when first exposed to air. Milling reactive metals dry and in air or a vented drum is more risky than necessary there is too much chance that fine powder will warm by mechanical action and chemical action then spontaneously ignite/explode.

Powders may get a treatment after milling this may be linseed (or other drying) oil, or chromate based passivation.

[portfire]

Thanks for both your post, very informative I won't be milling metals just yet arthur, as the oil is just for coating at the moment. I'll go for the raw oil digger, thanks again much appreciated

Dean

Edited by portfire, 13 April 2008 - 09:52 AM.