oldguy Posted July 10, 2011 Posted July 10, 2011 (edited) About to display my total ignorance in this area. Potassium Dichromate appears to be the only thing to passivate Mg, or Mg/Al when used with an AP comp. It would seem to me that water quenched 50/50 Mg/Al being an alloy would at least partly passivate itself with aluminum oxide. Why can't Mg/Al be further passivated with some form of anodizing electrolysis? Or, am I indulging myself in wishful thinking? Edited July 10, 2011 by oldguy
oldguy Posted July 14, 2011 Author Posted July 14, 2011 LOL… what did I do shoot a blank here? After reading up on Al & Mg, both can be anodized. So can magnalium. One could even do it in a home garage or shop, without very expensive equipment.(if you happen to have a big amp battery charger on hand, which I do) The process appears straight forward & not all that difficult.
dagabu Posted July 14, 2011 Posted July 14, 2011 LOL… what did I do shoot a blank here? After reading up on Al & Mg, both can be anodized. So can magnalium. One could even do it in a home garage or shop, without very expensive equipment.(if you happen to have a big amp battery charger on hand, which I do) The process appears straight forward & not all that difficult. I am all for it OG, please post your findings so I can ditch my Pot-Dich!! -dag
oldguy Posted July 14, 2011 Author Posted July 14, 2011 That’s the object so one doesn’t have to use Pot-Dich. It’s going to be awhile before I get it done & draw any conclusions. I’m a newbie at pyro, as well as anodizing. So, it takes some time to get up the learning ladder without missing any important rungs. Oddly, I find not knowing squat about certain subjects can have advantages. Since a person doesn’t know the normal do’s, don’ts & protocols. You assume about anything can be done & go from there. Often leading to useful innovations others never thought of, or thought not possible. I am assuming to do an effective job, the Mg, and/or Mg/Al particles to be anodized with an oxide layer will have to moving suspended in the solution so that they get a complete coating. I suspect that can be done with a fairly large capacity magnetic stir plate, or ultrasonic bath type cleaner. Fortunately, I have both. So, we will see. Trouble is, once done I suspect it would require some very sensitive instruments & considerable time to test the results. But, that’s down the road & to be dealt with, once there.
dagabu Posted July 14, 2011 Posted July 14, 2011 So, we will see. Trouble is, once done I suspect it would require some very sensitive instruments & considerable time to test the results. But, that's down the road & to be dealt with, once there. Yup, a cup of vinegar.... Trust me, you will know if you are successful. -dag
oldguy Posted July 14, 2011 Author Posted July 14, 2011 Ahah..... thanks for the heads up. Thats quick, easy & inexpensive.
FrankRizzo Posted July 15, 2011 Posted July 15, 2011 (edited) As I understand it, magnesium has a rather larger grain structure which makes any normal anodizing crack through fairly quickly. This is one of the reasons why magnesium is more reactive than aluminum. The dichromating bods to the surface more readily than a coating of magnesium oxide. What formula are you seeing calling for dichromated MgAl? Magnalium is fairly corrosion resistant on its own, and most of the formulas that I've seeing calling for dichromate in addition to the magnalium are simply formulas that used to use magnesium and have been substituted (keeping the dichromate unnecessarily) Edited July 15, 2011 by FrankRizzo
Mumbles Posted July 15, 2011 Posted July 15, 2011 I've never "dichromated" any MgAl, but I have added it as a solution to some compositions.
oldguy Posted July 15, 2011 Author Posted July 15, 2011 (edited) .What formula are you seeing calling for dichromated MgAl? Magnalium is fairly corrosion resistant on its own, and most of the formulas that I've seeing calling for dichromate in addition to the magnalium are simply formulas that used to use magnesium and have been substituted (keeping the dichromate unnecessarily) I want to use mgal in an AP comp. I know Mg is a no - no wth AP. Unless the Mg is passivated.I assumed mgal would also require passivation. I don't want to use Pot Dich to do that. Edited July 15, 2011 by oldguy
oldguy Posted July 15, 2011 Author Posted July 15, 2011 Vinegar + aluminum = no reactionVinegar + magnesium = reaction resulting in off-gassing and vaporous bubbling on the surface. Water quenching make a HUGE differance. check this out:
Mumbles Posted July 15, 2011 Posted July 15, 2011 Do you have any non-water quenched or commercial MgAl to compare against? MgAl is less reactive than straight Mg anyway no matter how it is quenched.
oldguy Posted July 15, 2011 Author Posted July 15, 2011 I used up all the commercial mgal I bought.I don't have any non-water quenched mgal left.I re-melted it all & water quenched it.
Mumbles Posted July 15, 2011 Posted July 15, 2011 Alright. I was just curious if it was a property of the water quenching that gave it resistance to vinegar, or if it was just that MgAl in general is resistant. Given that the milled and unmilled behave the same, I'd venture to guess that MgAl just doesn't react, at least not noticeably. I'm sure someone else could confirm that for you.
FrankRizzo Posted July 15, 2011 Posted July 15, 2011 (edited) I've still got a bit of magnalium that I made via the the original ingot-breaking process. I believe it will behave in the same way as the water-quenched variety. Magnalium is really quite stable. I'll test it in a few minutes. EDIT: Neither my crushed-ingot magnalium, nor some commercial -200m that I bought at PGI a few years ago reacts with vinegar! The camera's battery is dead, so no pretty pictures. If I have time tomorrow afternoon, I'll snap a few photos. Also, I've found the water-quenched material to be just as reactive in strobe and manganese dioxide rocket fuels as the crushed-ingot variety, so no worries about its usefulness. Edited July 15, 2011 by FrankRizzo
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