Magnesium Mites?

[cookies]

magnesium reacts to a lot of things causing oxidization and decomposition, it will never stop unless the material is removed to clean metal then sealed. Acidity and base swings will speed up the reaction, if set on certain types of rock while running it will embed into magnesium hence the concrete kills advice. It could have even been soured, contaminated or odd ph oil used for bar lube.

 

[ATpro]

The same thing can happen regardless of what the saw sets on. anywhere the saw has damage to the finish this is subject to happen. Gas, oil and other contaminants soak into the magnesium and the rot will start.

 

[3000 FPS]

Even though you say that saw has never cut any palm trees it has cut something that has a similar chemical in it that caused it to eat away at the magnesium. Maybe some kind of bush or other plant that you have there.
I have seen this before and it was always from Palm trees here in the US.
I have a Jonsered 670 that looks just like that.

 

[TRTermite]

Think it might depend on your local water quality a bit as well and if that water is hard water or soft water. If it is mineral deficient (the water) it will borrow any easily found and water carried minerals from whatever is at hand, thats why some brass plumbing fittings end up paper thin and tear rather than unthread.
Like you say, dry concrete with a good vapour barrier under and you might not see a problem, damp concrete often has the composition to go searching for minerals.
However, I do not see this as the cause here with this particular old 61, looks more mechanical damage to me- but I am only guessing.

I would suggest it may have been stored/abandoned on a crushed rock limestone floor or near a battery storage area. The plastic wasn't affected but some how an acid splattered/wicked up to the magnesium. as far as water and ph level concepts I understand that from some boiler experience.. But when fresh mortar or concrete gets wet it is the lime/lye that supercharges the acidity of your wicked up water. I am not a chemist but have done masonry enough to acknowledge seeing mortar salting from a wall. Apply that to a few of my saws and knowing their history gives me this notion.

 

[Bob Hedgecutter]

Yep, maybe this saw was used to cut some unknown and yet chanced upon by myself species over this side of the Pacific that selectively eats only the bottom edge of one side and front of the crankcase and leaves the clutch cover, oil pump area spotless- I will never know because I never knew the saws history.

However, the fact the screws that used to hold the front handle on have been muppet replaced with pop rivets, kind of lends me to believe it might have been mechanical after some force tore the handle off and stripped the bolts from the holes.
I know Husqvarnas love to play hide and seek with case fasteners, but not usually the ones holding the handle on and not usually both at once.
Had it been flood water or damp concrete- I would have expected to see more damage on the recoil side and possibly bottom of the clutch cover, more along the whole front of the oil tank.
But, like I say, who knows- unless you are the previous owner and recognise the damage.

Was never meant as a please explain post, more a whoops, look at this kind of post.
Hopefully the remedy will be available later this morning.

 

[BrettS]

Sorry, have to strongly disagree with that one- given I aint nowheres near Florida or the like- not a Palm grove within several thousand miles from here.

We do have Punga's here, about as close to a palm tree that we are gonna get.

 

[Yukon Stihl]

Sorry, have to strongly disagree with that one- given I aint nowheres near Florida or the like- not a Palm grove within several thousand miles from here.

Just disagree it's really not a big deal i took a guess

 

[3000 FPS]

Yep, maybe this saw was used to cut some unknown and yet chanced upon by myself species over this side of the Pacific that selectively eats only the bottom edge of one side and front of the crankcase and leaves the clutch cover, oil pump area spotless- I will never know because I never knew the saws history.

It could be that the saw had enough oil and saw dust covering the clutch cover and oil pump area that whatever it was did not affect it.

 

[dirtcurt]

Store it in the pool room with Chlorine?

 

[Joab]

I've got a related question if anybody knows the answer. I was thinking I somewhat understand this concrete and magnesium business; but then I got thinking about gas-powered concrete saws. They are usually based off a chainsaw and are covered in concrete dust for their whole life. How do they manage to hold up?

Envoyé de mon moto g power en utilisant Tapatalk

 

[calamari]

However, I do not see this as the cause here with this particular old 61, looks more mechanical damage to me- but I am only guessing.

It looks like mechanical damage to me too. Here's a link to magnesium corrosion from this site.

https://www.arboristsite.com/threads/magnesium-alloys.71834/

 

[calamari]

I've got a related question if anybody knows the answer. I was thinking I somewhat understand this concrete and magnesium business; but then I got thinking about gas-powered concrete saws. They are usually based off a chainsaw and are covered in concrete dust for their whole life. How do they manage to hold up?

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Excellent question Little Grasshopper.

 

[Jasonrkba]

It was stored on the floor and someone spilled vinegar around it.

 

[Bob Hedgecutter]

We do have Punga's here, about as close to a palm tree that we are gonna get.

So Brett, have you cut Pungas or even Cabbage trees with a chainsaw? I have mowed down acres of each and the sap does not eat saw cases, back in the day you could lower the boom on natives and nobody gave a toss. Yeah I see the obvious answer- but like I say, sap travel more than just the case bottom, right through the chain travel was perfect, so was the clutch cover I used for my "better" 61.

 

[Bob Hedgecutter]

I've got a related question if anybody knows the answer. I was thinking I somewhat understand this concrete and magnesium business; but then I got thinking about gas-powered concrete saws. They are usually based off a chainsaw and are covered in concrete dust for their whole life. How do they manage to hold up?

Envoyé de mon moto g power en utilisant Tapatalk

Concrete saws cut cured concrete with the aid of water to cool the diamond blade- a floor saw is often suspended in a dedicated cradle- after they perform the task at hand, they are often (or should be!) flushed off with clean water, or at least stored away somewhere that the cut slurry will dry- dry concrete will not eat a saw case like stored on wet/damp concrete will and many a dedicated concrete saw will not live long enough for case rot to show up!

 

[BrettS]

So Brett, have you cut Pungas or even Cabbage trees with a chainsaw? I have mowed down acres of each and the sap does not eat saw cases, back in the day you could lower the boom on natives and nobody gave a toss. Yeah I see the obvious answer- but like I say, sap travel more than just the case bottom, right through the chain travel was perfect, so was the clutch cover I used for my "better" 61.

Err nowhere did I mention I had cut punga's down or that was your problem Bob.

 

[Canyon Angler]

I think it's mainly the lime in concrete. Lime is a base (opposite of acid) and bases attack metals like aluminum and magnesium, especially in the presence of an electrolyte (water/moisture in concrete, dew, etc.), and especially where there are dissimilar metals (like aluminum/magnesium and steel) both in contact with that electrolyte ... some of it is likely caused by galvanic corrosion, the same thing that makes batteries work, and that makes zinc anodes on outboard motors get eaten away before the aluminum gets eaten away.

I've found modern pennies (copper over a core of zinc) lying in saltwater where they were almost paper-thin -- the zinc got eaten away by the copper. All you need for that to happen is for there to be a tiny nick in the copper cladding so that both the zinc and copper are in contact with the electrolyte (saltwater), and then it's just a matter of time before all the zinc disappears and all that is left is the copper. The farther apart the two metals are on the "galvanic series" (linked below), the faster this will happen, and the greater the voltage differential will be between the two metals as they corrode. Magnesium is more anodic (or less noble) than any other metal on the galvanic series, which is why the sacrificial anodes mounted on outboard motors used in freshwater are made of magnesium, or an alloy of it. (Zinc anodes are used on boats in saltwater because they last longer. If you used a magnesium anode on a saltwater motor, you could almost watch it melt away like a Popsickle.)

https://www.corrosionpedia.com/images/uploads/galvanic series noble metals.jpg

 

[calamari]

I think it's mainly the lime in concrete. Lime is a base (opposite of acid) and bases attack metals like aluminum and magnesium, especially in the presence of an electrolyte (water/moisture in concrete, dew, etc.), and especially where there are dissimilar metals (like aluminum/magnesium and steel) both in contact with that electrolyte ... some of it is likely caused by galvanic corrosion, the same thing that makes batteries work, and that makes zinc anodes on outboard motors get eaten away before the aluminum gets eaten away.

I've found modern pennies (copper over a core of zinc) lying in saltwater where they were almost paper-thin -- the zinc got eaten away by the copper. All you need for that to happen is for there to be a tiny nick in the copper cladding so that both the zinc and copper are in contact with the electrolyte (saltwater), and then it's just a matter of time before all the zinc disappears and all that is left is the copper. The farther apart the two metals are on the "galvanic series" (linked below), the faster this will happen, and the greater the voltage differential will be between the two metals as they corrode. Magnesium is more anodic (or less noble) than any other metal on the galvanic series, which is why the sacrificial anodes mounted on outboard motors used in freshwater are made of magnesium, or an alloy of it. (Zinc anodes are used on boats in saltwater because they last longer. If you used a magnesium anode on a saltwater motor, you could almost watch it melt away like a Popsickle.)

https://www.corrosionpedia.com/images/uploads/galvanic series noble metals.jpg

Excellent description of what may have happened although I still think it looks mechanical damage. I think the answer is lost in time because it's based I bet on the nature of the guy running the saw and how he treated it. There are people who can screw up a solid steel ball.

 

[Hermio]

What does concrete do to a saw?

Both acids and alkali will dissolve magnesium. Concrete is alkaline, especially when fresh. Still, it looks like the saw was bathed in it.

 

[Hermio]

Others are probably smarter. Couple rules instilled...don't store saws or batteries on concrete. All that I do know is that none of saws have any rot. Keeps saws mostly in cases. Otherwise old carpet floor mats.

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I keep my saw on a rubber mat designed to keep mud off the floor when putting boots down. It keeps oil from the saw off the floor.