Author Topic: Rust never sleeps  (Read 3662 times)

0 Members and 1 Guest are viewing this topic.

kitestrings

  • Hero Member
  • *****
  • Posts: 1376
Rust never sleeps
« on: August 27, 2018, 01:50:23 PM »
Our turbine has been furled for the better part of the summer.  This time of year we have ample PV output, and the winds comparatively are pretty light.

I was a little startled then, to run it a few weeks ago and heard what appeared to be a one per rev rub.  Upon inspection I found that a couple of the magnets had pretty serious rust started on the ends.  The noise was being caused by some larger sections of the magnet plating pealing off.  Remember when we used to pin playing cards to hit on the spoke of our bikes?


After talking to my paint buddy/neighbor:

I've attempted to remove as much rust and loose plating as possible.  This is a bit of trick for two reasons: 1) there's about enough room to just get in a piece of emery cloth between the magnets and the stator on either side, and 2) the larger pieces of plating are magnetized and tend to want to stay on the magnet surface. 

Next I wiped down with an acetone dampened rag.

Applied Permatex rust treatment.  Let dry 24-hours

Roughened surfaces (where possible) with scotch-brite pad

Applied epoxy primer

That's as far as I've gotten due to winds yesterday that prevented me from spraying until late day.

Next I'll mix the paint and hardner and give a go at that.

The tough thing is that I can't really hit the face of the magnets to speak of - hoping to at least get all the edges.

Adriaan Kragten

  • Hero Member
  • *****
  • Posts: 1154
  • Country: nl
Re: Rust never sleeps
« Reply #1 on: August 28, 2018, 03:32:15 PM »
Neodymium magnets are very corrosive. Normally they are protected by a thin layer of nickel but that isn't enough outdoors where they can become wet. So after gluing the magnets to the armature sheet, they should be protected by at least one layer of epoxy paint. The advantage of using epoxy is that it doesn't contain a solvent. Paints which contain a solvent get very fine holes in the paint when the solvent evaporates and water may penetrate through these holes.

kitestrings

  • Hero Member
  • *****
  • Posts: 1376
Re: Rust never sleeps
« Reply #2 on: August 28, 2018, 08:58:03 PM »
Thanks Adriaan.  I feel like we spent quite a bit of time and attention to the fit and finish on this thing.  What I hadn't planned on is the corrosion starting beneath the plating.  This is how they originally looked:

https://www.fieldlines.com/index.php/topic,147846.msg1024511.html#msg1024511



A couple things that might also help: 1) a weather shroud of some sort on top of the alternator.  It will never be raintight, but I know Chris O used to use a lexan shield on top of his alternators, 2) we might be better to let it free-spin while furled.  I normally shut it down by furling and then closing in the load bank.  This keeps it tame, if not stopped in light winds, so it has a tendeny to sit for long times and naturally it favors a 'favorite' position with even the slightest imbalance.  It seems to be mostly on two magnets that appear to favor the bottom position.

dnix71

  • SuperHero Member
  • ******
  • Posts: 2513
Re: Rust never sleeps
« Reply #3 on: August 29, 2018, 06:15:06 PM »
There is spray paint that is equivalent to cold dip galvanize. I have a can. It dries to 95% zinc. Neos rust, they don't last forever outdoors.  https://www.amazon.com/ZRC-Galvanizing-Compound-Aerosol-Z-R-C/dp/B00H9GPY7C#customerReviews ZRC is reported to be better than Rustoleum brand for adhesion.

tanner0441

  • Hero Member
  • *****
  • Posts: 1099
  • Country: wales
Re: Rust never sleeps
« Reply #4 on: August 30, 2018, 01:41:53 PM »
Hi

Has anyone tried Galvanic protection? I know that pipelines use it. Zinc strapped to the plate the magnets are mounted on.


Brian.

mab

  • Sr. Member
  • ****
  • Posts: 428
  • Country: wales
Re: Rust never sleeps
« Reply #5 on: August 30, 2018, 05:01:52 PM »
Hi

Has anyone tried Galvanic protection? I know that pipelines use it. Zinc strapped to the plate the magnets are mounted on.


Brian.

If I understand the process correctly that only works underwater/underground where the zinc and whatever it's protecting are electrically connected by the 'wet' completing the circuit - for magnet plates up in the air the magnets could be wet independently from the zinc - that's why galvanised roof sheets and the like can rust through in one place whilst there's still zinc on them a few inches away.

Of course it may (?) be possible to fix your neos to the plates then send them away to be galvanized? I guess hot-dipped might be too hot for the neos, but could electro-plating work?

tanner0441

  • Hero Member
  • *****
  • Posts: 1099
  • Country: wales
Re: Rust never sleeps
« Reply #6 on: August 31, 2018, 12:34:51 PM »
hi

I realised after I posted about galvanic protection and being under ground or submerged in weter.

When electronics are required in explosive atmospheres they are conformally coated in plastic or horrible silicone material that renders servicing all but impossible. Is there a conformal coating that would tolerate the conditions your magnet plate is operating under?

Brian

Jason Wilkinson

  • Full Member
  • ***
  • Posts: 181
  • Country: bb
Re: Rust never sleeps
« Reply #7 on: August 31, 2018, 03:49:13 PM »
As  long as the neo's are attatched directly to the steel  they will corrode /rust  i used a strip of vinyl  between  magnet and rotor  ( don't know if that lessens the magnetic flux passing or not) but those rotors last longer than those attatched directly  i am less than a mile from the salty  atlantic  so you would understand  how it impacts  us

MattM

  • Hero Member
  • *****
  • Posts: 1167
  • Country: us
Re: Rust never sleeps
« Reply #8 on: September 01, 2018, 07:38:12 AM »
Can you remove shavings with tape?

SparWeb

  • Global Moderator
  • Super Hero Member Plus
  • *****
  • Posts: 5452
  • Country: ca
    • Wind Turbine Project Field Notes
Re: Rust never sleeps
« Reply #9 on: September 01, 2018, 08:02:28 AM »
It's nice to see so many suggestions, but...
Now that the corrosion has set into the magnets, it's probably deep in there.  Magnets are sintered iron, with "magic" impurities.  The grain structure offers no resistance to corrosive attack if the plating is lost.  Any surface coating you add now without completely cleaning all of the magnet surfaces will just trap in the contamination.  It will continue to run for a while, but the longer it goes, the deeper the corrosion will get. 

Your generator should run until your grandkids graduate from university.  To get that many more years more out of it, I would dismantle the generator, thoroughly clean off the corrosion with coarse then fine sandpaper until I got a dull gloss finish, and then I would invest in a high-temp aerospace epoxy coating.  There might be other chemical treatments that would help, before the epoxy coating, but I have no idea what is appropriate on sintered iron.
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
System spec: 135w BP multicrystalline panels, Xantrex C40, DIY 10ft (3m) diameter wind turbine, Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024
www.sparweb.ca

MagnetJuice

  • Hero Member
  • *****
  • Posts: 557
  • Country: ca
Re: Rust never sleeps
« Reply #10 on: September 01, 2018, 11:24:21 AM »
Hi Fieldliners,

My first post. Here is a quick introduction. I discovered this forum about 9 years ago and have been visiting almost on a daily basis. I bought both of the latest Hugh Piggott's books and also Dan Bartmann's and Fink book on wind power.

At the moment I live in an urban area where I can't put up a tower. But that doesn't stop me from building some alternators to run some tests on them.

I am retired so I have a lot of time to play with magnets and copper wire.

I built a machine with a 1-inch shaft powered by a 3 HP 3-phase motor and controlled by a VFD that I can spin from about 100 to 650 RPM, and as fast as 1650 RPM if I switch pulleys. I also bought different sizes of Ferrite and Neo magnets and a few dozen Lbs. of magnet wire from 14 to 22 Ga. I am also working on a motorized coil winder. I don't want to kill myself winding lots of coils by hand.

So in the near future I would appreciate input from you guys (and gals) about what kind of tests you would like to see so we can obtain data that would benefit all of us.

Right now, I'm interested in this problem with rust on Neo magnets and with your help I would like to do a test in the real world environment. I looked around the Internet to see what's available and found some galvanized coating products made by SPRAYON, CRC and ZRC that look like good candidates to run a test with.

What I would like to do is this; I have a few extra Neo's 1.5 inch by .75 inch by .5 inch. I would like to attach 4 or 5 of them to a piece of steel and put them outdoors where they would be continually exposed to the elements. We get a lot of rain here through the winter months. I would leave one magnet unprotected, just with the Copper-Nickel coating that they come with. The rest of the magnets I would coat according to the suggestions from you guys. Then every few months I take pictures and post them. It would take a few years to see results but I think we could get some useful data.

If we find a way to protect Neo's, that would be great. Ferrites don't rust, but a powerful alternator using ferrites would be large and very heavy. Samarium Cobalt magnets don't rust either but they are less powerful than Neo's and cost about 3 times as much.

I saw kitestrings beautiful machine when he was building it, it hurts to see this happening to it.

kitestrings, what kind of coating did you put on those magnets when you built it?

Ok, that's it for now.

Glad to be here,

Ed
What can I do TODAY that would make TOMORROW a better world?

dnix71

  • SuperHero Member
  • ******
  • Posts: 2513
Re: Rust never sleeps
« Reply #11 on: September 01, 2018, 04:11:43 PM »
SparWeb said:
It's nice to see so many suggestions, but...
Now that the corrosion has set into the magnets, it's probably deep in there.  Magnets are sintered iron, with "magic" impurities.  The grain structure offers no resistance to corrosive attack if the plating is lost.  Any surface coating you add now without completely cleaning all of the magnet surfaces will just trap in the contamination.  It will continue to run for a while, but the longer it goes, the deeper the corrosion will get. 


If there are gaps in the grain, then a rusty magnet might be protected by adding rust converter in a pressure cooker. Coat the magnets in converter and hook up your pressure cooker to an air compressor and raise the air pressure until the pressure cooker vents and let it run for half an hour. Easy off on the pressure slowly until you are back to 1 atm at the end of the hour. Then coat in epoxy.

clockmanFRA

  • Hero Member
  • *****
  • Posts: 952
  • Country: fr
    • Renewable Energy creation
Re: Rust never sleeps
« Reply #12 on: September 01, 2018, 04:39:32 PM »
Hi KS,

Yes as 'Sparweb' says, once the neos original coating is damaged or has separated from the magnet it self, then normal paints etc will not stop the corrosion.

I have found some of my neos were rusting when they came from the supplier as new!

Have a look at a metal conservation techniques that are used by the Museum world.

I work in the conservation world and work on metal surfaces that have corrosion, so I trust my comments below will be helpfull .

Firstly I remove the neo magnet.

1. ........ First treatment is total immersion in a hydrochloric solution, (rust remover). Time of immersion depends on the amount of corrosion present. Strength of solution depends on amount and depth of corrosion.
Once out of the solution then hand brushing using soft brass or stiff bristle brushes to remove the corrosion particles.

Keep repeating this process until corrosion is pacified, but do not get over zealous with the brushing.

2.  ........ Using cotton swabs remove excess corrosion treatment chemicals.

Immerse in an ammonia solution, I use a 8 to 1 horolone mix with deionised water. Deionised is important.

Time of immersion should not exceed more than 20 minutes or the ammonia will attack the metal.
Again bristle or brass hand brushing.
Repeat this process if required.

3. ...... Remove excess fluid with cotton swabs.
Immerse the magnet in isopropanol alcohol for up to 30 minutes, then bristle brush with isopropanol alcohol.
Repeat this process until there is no discoloration in the fluid. If there is then go back to process 1.

The final rinse should be in a new uncontaminated batch of isopropanol alcohol.
 
4 ...... Drying.
Remove excess fluid with new cotton swabs.
Without touching the magnet now put it on a gentle heat. I use an electric storage heater with a fresh new piece of 80 gram white paper. This also shows up on the paper if the magnet is still leaching the cleaning chemicals.

Drying can be as long as possible 24 hours should be seen as a minimum with each of these Neos.

Do not touch the magnet with your bare hand/skin as you will leave microscopic sweat/moisture on it.

You can use chalk on a very soft bristle brush to remove any isopropanol alcohol residues after drying,  but wear gloves.  Soft brushing with chalk is important to remove any drying chemicals on the surface so the epoxy resin has better adherence to the metal surface.

Now coating the neo.

I use a thin viscosity epoxy resin.  But chalk brush just before coating and very very soft brush brushing to remove any chalk dust before coating the neo.

I understand that vinyl ester resin is porous to moisture, but standard resin is not, but then its not UV stable. !!!!!!! 

Brushes .... keep a separate clean brush for each process, normally about 6 different brushes.

At all times use Nitrile or latex hand gloves and sufficient ventilation.

I trust this helps?
 
 


 
Everything is possible, just give me time.

OzInverter man. Normandy France.
http://www.bryanhorology.com/renewable-energy-creation.php

3 Hugh P's 3.7m Wind T's (12 years) .. 5kW PV on 3 Trackers, (8 yrs) .. 9kW PV AC coupled to OzInverter MINI Grid, back charging AC Coupling to 48v 1300ah battery

SparWeb

  • Global Moderator
  • Super Hero Member Plus
  • *****
  • Posts: 5452
  • Country: ca
    • Wind Turbine Project Field Notes
Re: Rust never sleeps
« Reply #13 on: September 03, 2018, 04:48:15 PM »
Hi MagnetJuice
Welcome to Fieldlines!
Feel free to make a thread of your own and share what you've been working on.
I'm concerned as you are about the corrosion and for the same reasons - Kitestring's genny is such a thing of beauty, I hate to see it marred!
Hold off before sacrificing any of your own magnets, for a while.  I would like to see more of KS's investigation before deciding he didn't adequately protect them.  At this time I believe his magnets, as purchased, may have come with defective plating.  This opinion is partly based on the care he put into the rest of the project, and that I've had some generators with similar paint coatings that didn't rust over as much, and some magnets I've bought had chipped plating.


Clockman,
That's a very thorough process!  To be complete the HCL solution needs to be cleaned more thoroughly than deionized water can do at room temperature, so I would recommend heating the water to at least 80C (190F) to be sure.  That comes with consequences though....  The HCL process basically forces KS to remove the magnets from the rotors.  Any HCL left that infiltrates between magnet and rotor will just eat away from underneath.  Until it is certain that all of the magnets have to come off,  I'm still trying to think of a way to fix it without going to that extent.  If it does become necessary to remove all of the magnets, then your process would work.

But, if removing the magnets, could it be cheaper to just get new magnets, eh?

No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
System spec: 135w BP multicrystalline panels, Xantrex C40, DIY 10ft (3m) diameter wind turbine, Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024
www.sparweb.ca

MagnetJuice

  • Hero Member
  • *****
  • Posts: 557
  • Country: ca
Re: Rust never sleeps
« Reply #14 on: September 04, 2018, 12:35:32 AM »
SparWeb, thank you for the welcoming and thank you for all your contributions.

That was a very informative post from Clockman.

I do have some concerns with the temperatures that you are recommending for the hot water to wash away the hydrochloric acid. Neodymium magnets start losing their magnetization at about 80C. It would probably be wise not to exceed 70C.

Yes, I think it would be cheaper to remove the rusty magnets and replace with new. If it was my alternator, that is what I would do. Then coat the complete rotors according to Clockman's instructions.

Clockman:

I'm not sure what you mean by “standard resin”. Do you mean polyester or some other type of epoxy? Also, how do you thin the resin to make it easy to apply with a brush? And would it be a good idea to coat the rotors with standard resin and then put another coat of vinyl ester to protect from UV?

I suspect that rust starts to develop in Neos because of the moisture that is on the magnets before they are coated. Not only moisture, but also other impurities from improper handling. I totally agree with Clockman's meticulous ways of preparation before coating. If we are careful not to leave moisture on the magnet-rotor combination, and then coat it proper to keep moisture out, these Neos could last many years. Could anybody suggest a way to reduce ambient humidity before coating? Relative humidity of between 20 and 30% would be ideal. IF that is possible.

SparWeb; Yes, I will start a thread when I have something to contribute. Right now all I have done is learn a little from books and from this forum and build the machine for testing as described in my post above. My motorized coil winder is near complete. The tests that I'm planning on doing are to find out the best metal thickness for rotors for different strength magnets; find the ideal coil thickness for better utilization of the magnetic flux; tests to compare alternator output when magnets are placed closer or farther from each other on the rotors and things like that.

In a nutshell, I want to find the best way to optimize the components and construction to build efficient systems. I want to extract all the juice that the magnets are able to produce. That way, when I move way from this urban area, I can fly a nice machine on top of a 300 Ft. tower… WHAT???  300 Ft.? Nah, maybe 80 Ft.  :) One thing is for sure, I'll share the test results as I do them.

Ed
What can I do TODAY that would make TOMORROW a better world?

clockmanFRA

  • Hero Member
  • *****
  • Posts: 952
  • Country: fr
    • Renewable Energy creation
Re: Rust never sleeps
« Reply #15 on: September 04, 2018, 02:52:02 AM »
Hi MagnetJuice, and welcome.

Yes I mean standard fibreglass resin as 'Polyester' type.

The resins are many and have various properties, and my empirical experiences with resin types are limited.

As I said, I use an epoxy resin that has a thin viscosity, they come like that, (used by the jewellery trade for potting up).  I use it with my Ozinverter 6Kw toroid constructions coating between the secondary windings.

As its thin viscosity I can paint on one side and the edges,  as the magnet is supported on 3off non-magnetic stainless steel 4mm dia radiused pointed supports. Just use a small fine brush for application of the epoxy.  24hours later and well set, I reverse and do the other side.
Interestingly the fumes seem to get underneath and some times the supports are just tacky even though there is no physical application of the epoxy on that side.

I normally do my Wind Turbine stator and magnet discs with Polyester and then coat with a coloured (white) vinyl ester. Its not perfect and there are problems around physical orifices and washer clamping, where the dreaded moisture and rain can get a foothold.

I do not see a problem with a warm rust solution, but all other chemical treatments that I list should be normal ambient temperatures.         OR you get what we call 'Temperature Staining' on the metal because of heat differentials being extreme.

Hi Sparweb,
The ammonia solution is the buffer, degreaser and neutralizer.
YES far easier to buy new Neos, but have you seen the price nowadays !!!!!!!
« Last Edit: September 04, 2018, 03:01:16 AM by clockmanFRA »
Everything is possible, just give me time.

OzInverter man. Normandy France.
http://www.bryanhorology.com/renewable-energy-creation.php

3 Hugh P's 3.7m Wind T's (12 years) .. 5kW PV on 3 Trackers, (8 yrs) .. 9kW PV AC coupled to OzInverter MINI Grid, back charging AC Coupling to 48v 1300ah battery

electrondady1

  • SuperHero Member
  • ******
  • Posts: 3120
  • Country: ca
Re: Rust never sleeps
« Reply #16 on: September 04, 2018, 07:36:00 AM »
if your in the states you can still get "extend"  a latex based product that turns iron oxide into iron sulfide. works very well to stop corrosion.
they also have a product at home depot called "correseal."

you can't get that here in Canada . but lepages puts out something called rust converter that works in a similar manner. 

dnix71

  • SuperHero Member
  • ******
  • Posts: 2513
Re: Rust never sleeps
« Reply #17 on: September 04, 2018, 08:48:05 PM »
electrondady1 I've used Extend before, but it is not abrasive resistant. I don't think it would last long on something moving around, even if you painted over it. It looks like Amazon will ship the liquid to Canada. Maybe the aerosol is banned.

https://www.amazon.ca/Loctite-8-Ounce-Extend-Neutralizer-1381192/dp/B001000VS0

electrondady1

  • SuperHero Member
  • ******
  • Posts: 3120
  • Country: ca
Re: Rust never sleeps
« Reply #18 on: September 05, 2018, 07:16:35 AM »
i would not use extend as a  finish but as a base coat to stop the oxidization process. you can put an  epoxy or urethane enamel over top .

kitestrings

  • Hero Member
  • *****
  • Posts: 1376
Re: Rust never sleeps
« Reply #19 on: September 05, 2018, 10:56:00 AM »
Folks,

Thanks for all the comments.  We just had a very localized, but severe storm here - no turbine damage - but, it has taken me a while to get back to this post.

First off, the turbine is still working well, and I'm realizing that it has been up now for (can it be?) five years now.  Unlike my truck that gets tucked into a garage each night, this things out there day in - day out in the elements.  Rust is inevitable.


That said, it appears to be something that got its start below the plating as SparW suggested. There were two magnets in particular that had significant rust where the plating on the ends was separating.  All of the repairs this round were done ^^up there^^, so baking, drying, removing magnets... will be solutions for another day when we have to take it down for some other reason.  This was my arsenal:
11412-1
Those little Preval cartridges worked pretty well and allowed me to use something more durable than over the counter primer & paint, without having to haul a portable airtank up the tower.  The I also used Permatex Rust Treatment 81849 as a neutralizer/base coat for the areas that I couldn't get to otherwise, as electrond suggests.

Welcome to the forum MJ.  Regarding your question of how we prepped and painted...the plates were sandblasted, de-greased, epoxy primer, Concept DCC finish, stainless fasteners.  There is a possibility water may be trapping beneath the magnet rings, though we tried to seal it all, notice I also applied a thin bead of silicone around the magnet edges.
11413-2

11415-4
« Last Edit: September 05, 2018, 03:22:00 PM by kitestrings »

Mary B

  • Administrator
  • SuperHero Member
  • *****
  • Posts: 3169
Re: Rust never sleeps
« Reply #20 on: September 05, 2018, 07:40:09 PM »
The thin bead of silicone could have started your problem! Many use an acidic cure compound(that acetic acid smell). You may have used electronics grade that is safe and not acidic... just a thought...

kitestrings

  • Hero Member
  • *****
  • Posts: 1376
Re: Rust never sleeps
« Reply #21 on: September 06, 2018, 11:09:40 AM »
Quote
The thin bead of silicone could have started your problem!

...geaze, I really don't think so.  The silicone was applied after things were fully cured.  During the assembly I was just thinking it might help prevent any migration along a pinhole between the magnets and the rotor plates, or where water might sit on the edge of the magnet rings.

Below is a larger piece of the plating that I removed from one of the two magnets that I described.  You can see where I bent it to test the paint bond.  It was pretty solidly adhered to the plating.
11421-0
11422-1

XeonPony

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 888
  • Country: ca
  • Sanity is over rated!
Re: Rust never sleeps
« Reply #22 on: September 06, 2018, 11:32:38 AM »
I preheat any of my paint work to 150f in an oven, then once warm to the touch I start the priming (Touch through a glove)

Once the first prime has had time to cure I re-coat the now cooled piece with enough primer to fill in any visible voids, this is allowed to fully cure to the recommended time, then I prep for the surface coat.

The preheating ensures the entire unit is as dry as possible, this is in a dehumidified room as well, the more care full your prep and pre-coating is the longer term it will hold up!

Then hit it with a high quality clear coat/moisture barrier. I learned this from growing up around salt water!
Ignorance is not bliss, You may not know there is a semie behind you but you'll still be a hood ornimant!

Nothing fails like prayer, Two hands clasped in work will achieve more in a minute then a billion will in a melenia in prayer. In other words go out and do some real good by helping!

DanG

  • Hero Member
  • *****
  • Posts: 1122
  • Country: us
  • 35 miles east of Lake Okeechobee
Re: Rust never sleeps
« Reply #23 on: September 06, 2018, 02:54:54 PM »
Drying the magnets after being in service a while? Might be best to do like firework makers do, they assemble stuff damp then leave in sunshine and cover after peak sun hours are over, repeating until dry...

I have used canning jars with loose lids, honest air gap on seal, then close up tightly while still hot - and repeat a few days. If you leave a desiccant pack in it when you close it up as it cools it will pull a vacuum inside jar and doubly help evacuate moisture...

I've got a magnet sweep I made up from 1" x 0.125" N-42 neo discs - their composition is more like ceramic and the plating totally failed on about 1/3 of them by being out in the shed w/ condensation etc for 10 years(!) - I had to rebuild it the other day, plywood & adhesives had failed, so it got me thinking...

To clean them up? Just gnarly duct tape to pull off any scale remaining, then again and again until rust colors stop transfering - then POR-15 moisture cure paint for two coats, then a top coat of something while the POR had not cured glass hard yet else nothing will bond with it, even more POr-15.  This paint pull moisture from the air to catalyze and would draw out much of the remaining humidity from the neo composition - the penetrated coating continues hardening longest after the surface has locked up. I would NOT introduce ANY new chemistry into their composition, no phosphate, no zinc, no chlorides - just eliminate as much live hydrogen oxide possible and seal it up...

Included is a photo of Sweep Revision 2 - next time I have POR-15 open I'll dunk the works. Note zero wood involved, last long time.

MagnetJuice

  • Hero Member
  • *****
  • Posts: 557
  • Country: ca
Re: Rust never sleeps
« Reply #24 on: September 07, 2018, 02:10:12 AM »
Hi KS, thanks for responding. Nice useful pictures too. That treatment that you put on the rotors and magnets should've been adequate, but evidently it was not enough protection.

What I think is happening is this; it seems that the coating that the manufacturers are putting on the magnets, as good as it is, it is not adhering well to the sintered iron-neo-boron mix.

But I suspect that the main problem could be a difference in the rate of expansion of the two materials (the sintered iron mix and the copper-nickel plating) with changing temperatures. If the iron mix expands at a faster rate than the copper-nickel plating, the plating will crack. Once this happens, water comes in contact with the sintered mix and corrosion starts. Even the water vapor in the air could be enough to start corrosion when in contact with the unprotected magnet.

I'm not an expert on this, so this is speculation on my part.

I did a bit of research earlier and found a discussion about rusty magnets on this forum from 2006 in which Les Vincent (Flux) R.I.P., and others, took part and had some interesting suggestions. I understand that Flux used to work fixing some damaged rotors, among many other things.

I'm not sure if I am allowed to post links since I don't have enough posts yet, but here it is:

https://www.fieldlines.com/index.php/topic,138006.msg913546.html#msg913546

After reading all that, I'm beginning to think that the best protection for new magnets would be encapsulating the magnets in a good quality epoxy. That way, even if the copper-nickel plating gets cracked or damaged, it would still be protected by the layer of epoxy.

There are many different types of epoxies. Hopefully someone with good knowledge of epoxies reading this thread could recommend something appropriate for this application.

Another thing is isolation between the steel rotor and the magnets. That has been discussed before and was mentioned earlier by Jason. That could be accomplished by a thin sheet of vinyl or Polycarbonate, (Lexan-Plexiglas)

I found a website that sells clear rigid vinyl sheets in thickness of - .01, .015, .02, .03.  Prices are from 6 to 15 $US for a 21 x 51-inch piece.

Another website sells Clear Polycarbonate, .031" thick X 24" X 48" for around US$22.

The tricky part would be; how to encapsulate the magnets in epoxy during construction? Hard to do but not impossible.

It is late here, I'm tired.  :-\

Ed
What can I do TODAY that would make TOMORROW a better world?