Magnesium corrosion

[bama]

I have a crankcase that has experienced a corrosion of some type. At the very bottom of the crank, there is a white powdery substance that has replaced the clean metal. I have cleared it out with a wire brush, but about 1/2 the thickness of the metal is gone. Is this case destined for the recylcle pile and what causes this kind of corrosion/rust?

 

[Big feller]

I have a saw (045) that has pretty serious corrosion. There was a bad patch underneath over an inch across, and when cleaned up his became a hole about quarter of an inch in diameter. This was through to the oil resevoir.

I made a temporary repair with woven glass cloth and epoxy and then finished by sanding and painting. A few weeks later I bought a parts saw for a replacement crank case. Over two years on the repair is holding well. Replacement case still on the shelf.

My guess is that a previous owner kept the saw in a damp shed on a steel shelf, so it suffered some sort of catalytic corrosion.

If you don't yet have any holes I would suggest you repair with car body filler and paint carefully to protect it. As ever, preperation is everything.

Good luck!

 

[DGG]

I don't know but it sure sounds like electrolysis corrosion of some sort.

http://www.scienceteacherprogram.org/physics/Peter06.html

Had the saw been sitting unused for a long time?

It's didn't eat the rings an make metal filings did it?

 

[Big feller]

Just confirm fo us - Is the corrosion on the outside of the case or internal to the saw. I am assuming the former.

 

[andrethegiant70]

I've found that concrete floors are really not the best place for magnesium chain saws either. If they don't speed up corrosion through moisture and conductivity, given enough cycles they will abraid metal badly. I have an xl-12 with a leaky tank that looks like it has simply been scuffed to death. I put all my saws on wood now.

 

[habanero]

My 955 had a hole through the gas tank similar to those described above-white powder removed to find a hole. I used some gas tank epoxy from O'Reilly's, expecting it not to last too long. So far it's still holding up well. I think if you get the edges of the hole cleaned well and use the fiberglass matting to reinforce the repair, holes can be fixed relatively easily.

 

[bama]

Just confirm fo us - Is the corrosion on the outside of the case or internal to the saw. I am assuming the former.

Corrosion is inside the case, under the crank. But, it has not corroded through. It goes about 1/2 the thickness of the case(I had the crankcase apart).

 

[bama]

I've found that concrete floors are really not the best place for magnesium chain saws either. If they don't speed up corrosion through moisture and conductivity, given enough cycles they will abraid metal badly. I have an xl-12 with a leaky tank that looks like it has simply been scuffed to death. I put all my saws on wood now.

I bought a 621 that had sat on a bag of dry fertilizer. It completely disintigrated the case up to the area under the crank. Got a good p/c out of the deal, at least.

I keep all my saws on the shelf!

 

[bama]

I don't know but it sure sounds like electrolysis corrosion of some sort.

http://www.scienceteacherprogram.org/physics/Peter06.html

Had the saw been sitting unused for a long time?

It's didn't eat the rings an make metal filings did it?

It was a saw I bought on eBay, but the condition was represented well. Saw had been sitting(somewhere way down South). Ring was stuck, but piston was good.

 

[Big feller]

Corrosion is inside the case, under the crank. But, it has not corroded through. It goes about 1/2 the thickness of the case(I had the crankcase apart).

I think I would be tempted to just clean up and paint. The thought of bits of filler coming loose inside the combustion chamber is not a pretty one!

I will be interested to see what the experts thinkopcorn:

 

[bama]

THis is my "beater" saw right now. It is a 625 that I got for almost nothing. I was thinking that if I got the loose stuff off, I should be fine. I used a wire brush on my drill(brass bristles) and took it to shiny metal.

I was thinking I should give it a whirl and see what happens. The worst that could happen would be taking out a main bearing with a piece of metal. I wouldn't do that with my other ones, but this one could be my "test". I sure would like to know what caused all that corrosion, though.

 

[Lakeside53]

Salt water and palm juice are the two I know.. Had an MS460 in for service from a Florida ebay purchase... Clutch side cover eaten though, corrosion everywhere.. Bought an 026 from Huston once.. bad... used and entire tube of JB weld fixing it..

 

[adkranger]

Salt water and palm juice are the two I know.. Had an MS460 in for service from a Florida ebay purchase... Clutch side cover eaten though, corrosion everywhere.. Bought an 026 from Huston once.. bad... used and entire tube of JB weld fixing it..

Yeah, just ask Ekka 'bout them nasty Palms....... :greenchainsaw:

 

[Cedarkerf]

I work in the airplane business putting aluminum and magnesium on cement floors big no no. FAA gets quite fussy about it. My saws have always sat on wood shelves no sign of corrosion.

 

[bama]

Salt water and palm juice are the two I know.. Had an MS460 in for service from a Florida ebay purchase... Clutch side cover eaten though, corrosion everywhere.. Bought an 026 from Huston once.. bad... used and entire tube of JB weld fixing it..

Maybe this saw has been on the wrong side of a hurricane.

 

[adkranger]

Maybe this saw has been on the wrong side of a hurricane.

Like all them "discounted" cars & trucks they were draggin' up north a year or so back. Looked fine on the outside, till ya look inside to see no carpeting, headliners or sound absorbing material.:help: Kinda makes one wonder how much flood merchandise got spread across the land to the unsuspecting.......

 

[jonseredjohn]

I have seen this happen in the fuel tanks of Homelite saws.The cause would seem to be the use of alcohol (gas line anti freeze) or ethanol blend fuels.

 

[Sprig]

Salts (salt air/water around here), dissimilar metals (ie filings and steel crap inna tank), and/when even touching a dissimilarly charged surface (ie a nail, concrete surfaces, etc.) will eat away softer metals imo; like how batteries work. My feelings is that painting alum. and mag. surfaces is to prevent this contact. Stand to be corrected by all means from those with some real knowlege but having dealt with some weird corrosion probs on boats around the chuck this makes sense to me.

My drunken 0.02$ worth fer the evening. And guessin'.



opcorn: