Author Topic: Rusty magnets? (Read 7242 times)

alibro · « **on:** October 13, 2006, 08:55:11 PM »

Hi guys

I have finally started work on rebuilding my old wind turbine and the first job is to dismantle the old one. I decided to rebuild it from scratch including refitting the magnets to the old rotor. The resin chipped away from it pretty easily and as I never glued the magnets on they weren't too hard to remove. Problem is that several of the magnets have the nickel damaged on one side and are rusted. I cleaned them up with a wire brush to get rid of it but I am concerned that it will return if not treated. Can I just paint them with Hammerite or something similar? If I do paint them will it cause any problems with the new resin?

I also noticed quite a lot of rust on the brake disk under the resin which is probably why the resin came away so easily. Should I paint the brake disk before fitting the magnets or is there another way of stopping the rust creeping in?

Cheers

Any advise much appreciated

vawtman · « **Reply #1 on:** October 13, 2006, 03:53:11 PM »

Alibro when the mags are dry does the rust seem gooey between the coating and the mag?In other words can you smear it?

DanG · « **Reply #2 on:** October 14, 2006, 07:36:46 AM »

ANY collision of neos damages the underlying pressed powder matrix. Buy extras to play with but only handle the working ones like they are hummingbird eggs. Part of the high cost of them is paying for man'f & distributor aggravation in getting them to you without ever being damaged by mishandling.

My first repair of damaged nickle plate on a neo was using the thinnest of lacquers to try and get penetration into the pressed matrix, and it seemed to stall corrosion if I used 6 or 8 coats - but that within hours of the damage.

If I had a large magnet I needed to save to keep the set together I would heat it for a day in sunshine on a dry window ledge (not kitchen oven) and douse it with a thin lacquer and then do the wire brushing so to keep a barrier from air reaching any undamaged composition, adding more lacquer as I went and then getting 6 or more coats of lacquer on during the next few days. The granules will be moving, or creeping ever so slightly from huge internal stresses of N grade magnets so there has to be enough coats to keep sealing the new fractures AND provide a strong enough build up to encapsulate the 'wound'.. .

vawtman · « **Reply #3 on:** October 14, 2006, 12:23:44 PM »

I wonder is it possible to remove the nickel coating?Nickel,steel,moisture not good.

Epoxy coated better.

Has far has the rotors go just remove loose rust and set mags in long cure epoxy dont prepaint.

I compared jb weld and golf club epoxy(8hr set time)For mags.

The jb mag came of like it wasnt there

The Golfsmith shafting epoxy one is probably going to need a torch to loosen it.

Didnt want the mag to splinter and who nows what would happen then?

No need to encapsulate the mags in resin use them for cooling.

My opinion

alibro · « **Reply #4 on:** October 14, 2006, 02:09:14 PM »

Hi Vawtman

It isn't gooey, more just like rust. I deliberately scraped off the nickel plate where it bubbled and cleaned any rust with a wire brush. Some of the magnets were damaged by rubbing when the stator burned up and as it lay outside for a while they got a bit rusty. It is hard to be 100% sure the rust is all gone and I don't want it to come back. I was thinking of using something like rust eater and then coating them with the rubber sealent used for cars or just painting them with hammerite . I was worried how this would effect them when sealed in resin.

vawtman · « **Reply #5 on:** October 14, 2006, 02:41:45 PM »

Alibro just wondering how hard it would be to remove the coating from the infected mags.Likly the rust has penetrated deeper inside and will bubble over time.

I wouldnt use any acid based so called rusteater on them.Has a matter of fact please dont.

Dont use rubber sealant itll trap moisture.

No need for the hammerite, epoxy hates water especially the long cure type.Coat with that.

Dont seal in resin your inviting moisture in.Opinions again

V.....

rickysmartz · « **Reply #6 on:** May 13, 2013, 07:59:56 PM »

Hi Vawtman,

This is an old thread but I came across it when trying to solve my rusty neo problem.
Im just wondering why you advise against using a rust converter as the first step in halting further corrosion prior to recoating? This is exactly what I was planning to do as one of my triple coated neos has started to swell.

For reference-
12mm x 380mm steel rotors double coated in two pack epoxy primer, zinc rich
then superglue for mag positioning
then stainless banding and West system epoxy potting to 3/4 the depth of the mags (no epoxy on magnet top surface)
then 4 coats of 2 pack epoxy
then Lanolin spray

I thought this would be enough but its a bit damp here in Ireland!
How would you proceed? Anyone?

Thanks
Richard

fabricator · « **Reply #7 on:** May 13, 2013, 08:20:06 PM »

Put your rotors together and coat with POR-15, it seals out oxygen, no oxygen, no rust.

just-doug · « **Reply #8 on:** May 13, 2013, 09:30:15 PM »

my choice would be to west syetem epoxy the mags in place.let that set up.then use a cheap throw-away brush and fresh batch of more epoxy to paint the mags.then paint the whole thing with any paint that works for you.

Flux · « **Reply #9 on:** May 14, 2013, 02:50:28 AM »

This is a big issue in damp climates, it doesn't seem to be any problem at all in other climates.

My finding is that potting in polyester resin is a sure way to disaster, my suspicion is that moisture gets between the magnet and rotor disc and electrolytic corrosion starts. I also think the nickel plating is a flawed process and unless you can keep it perfect it really doesn't give much protection.

I had serious problems with polyester potted magnets and the corrosion was dreadful. One of those scrap magnets has sat outside now on a wall for several years, the nickel has now gone completely but the rust has not progressed much and it is not much worse than when I threw it out.

My conclusion is don't pot in polyester, probably don't pot at all but if you try it, use epoxy. I have a feeling that a thin coat of epoxy, which remains flexible is far more likely to succeed. I have tried POR 15 on one rotor and so far it is ok, I suspect this could be the best option.

If you have to use a glue to hold the magnets then make it epoxy. If you have some means of preventing the magnets from flying out the best method is to use POR 15 on the rotor plate, a film of POR 15 on the magnet surface that touches the plate( let totor plate dry before adding magnets). Finally a couple of good coats of Por 15. Possibly some form of flexible coating over that may be beneficial but as long as you don't damage it physically the POR 15 seems to be very durable.

I suspect yhat if you can absolutely prevent moisture from penetrating between magnet and steel plate there is no issue. In the real world this is most likely an impossibility so I suspect a non conduction barrier between magnet and steel is a wise thing to aim for. I also have a suspicion that epoxy coated magnets may be far preferable to the nickel.

My experience on the repaired rotors needs more time to evaluate but it seems as though the thin epoxy method and the POR15 method have dealyed the problem well even starting with damaged magnets. With new magnets and this treatment it looks as though you may get a sensible working life.

If you are in a reasonable climate, as long as you avoid the polyester potting, magnet life may not be a factor. In a damp climate with nickel plated magnets potted in polyester neo is not really viable, with a life of only about 3 years.

Flux

tecker · « **Reply #10 on:** May 14, 2013, 07:28:35 PM »

I'm using Ospho after some Brushing and ductape

kenssurplus · « **Reply #11 on:** September 24, 2013, 03:08:59 PM »

I would agree with flux at this point about the polyester. My climate is in the western U.S. desert. I have a 12 magnet per rotor machine I am presently rebuilding. The polyester failed on both magnet rotors and the stator. One rotor had the magnets completely potted, and the other one had the resin just to the top of the magnets. The rotor that was completely potted had three magnets that the nickel plating had split / swollen / or disintegrated. The rotor that had resin up to the top of the magnets had 5 magnets that had failed similarly. Because of the polyester warpage / cracking / and the expensive magnet loss, I nearly abandoned axial flux alternators completely. However, all of my other alternatives I tried were even worse in terms of performance and / or reliability.

Right now I am very hesitant to proceed with this rebuild (fourth rebuild of the same machine 1- magnet rotors disintegrated, no restraining stainless steel. 2- stator burnout. 3-stator warped and cracked 4- magnet rotors swollen, magnets bad) unless I can feel assured that I can keep this rebuild together much longer than the others.

Thanks for the previous posts and suggestions, please share your successful methods of dealing with this issue so that I can have some glimmer of hope.

tecker · « **Reply #12 on:** September 24, 2013, 06:36:42 PM »

Sand blast them is your best bet then then dip them in epoxy .

fabricator · « **Reply #13 on:** September 24, 2013, 06:52:58 PM »

I've never had a problem, JB weld the mags to the rotor, paint the whole thing with a good epoxy and call it done, I have never felt good about potting the mags, if your potting material breaks down it just gives water a place to get in and sit and do damage.

Frank S · « **Reply #14 on:** September 24, 2013, 08:35:58 PM »

Use KBS Rust blast then JB weld the mags to the rotor then paint with KBS rust seal

http://kbs.justoldtrucks.com/

jlt · « **Reply #15 on:** September 25, 2013, 12:00:11 AM »

I have been in the auto body trade and found that you need to seal all metal with a 2 part zinc chromate epoxy primer .

and on all the machines I have built I painted the rotors with automotive paint before installing mags

also I used urethane windshield to secure the mags. Never had any rust problem.

Just smear around all the edges of the mags to stop all moisture getting under No need to glue the mags

And if you ever need to remove them just use a stainless knife.But never try heat.It will ruin them

Flux · « **Reply #16 on:** September 25, 2013, 03:54:56 AM »

As an update to my post above, I have recently had a chance to look at one of the machines that I removed the polyester and painted with Hammerite rust beater and good conventional paint.

This suffered badly after only 2 years service, I replaced two really bad magnets and cleaned the rest best I could, it has now been something like 3 years and there is no obvious problem.

The machine treated with POR 15 is running fine but I haven't had a close look at it.

The conclusion seems to be that potting in polyester is worse than no protection. Starting with new magnets and using epoxy or POR 15 should give a much more useful life. I strongly suspect there is an electrolytic problem between the steel and nickel when permanently wet and an insulating covering to the steel discs is very beneficial. Similarly I suspect epoxy coated magnets will be better than nickel.

Flux

DanB · « **Reply #17 on:** September 25, 2013, 06:07:44 AM »

I've suspected this for a while Flux I'm glad to hear your experience.
pretty firm believer for a while in not letting metal touch metal and not potting the magnets.

kenssurplus · « **Reply #18 on:** September 25, 2013, 09:48:09 AM »

Hi All,

Thanks for the replies with good sound methods bourne of experience. I forgot to mention that on all the affected magnets, the corrosion / splitting / swelling was on the surfaces away from the steel rotors. Also the ethyl cyanoacrylate glue that I used around the edges of the magnets had made a glue layer under the mags between the steel and mags originally holding them on very firmly, but when I pulled the mags off after all the corrosion, there seemed to be no gluing action with the cyanoacrylate glue, as it just fell off when I touched it. So as you can see, metallurgy and chemistry were not my strong points here.

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Author Topic: Rusty magnets? (Read 7242 times)