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LAN_403

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Thu Mar 21 2019, 12:32PM

Registered Member #54278 Joined: Sat Jan 17 2015, 04:42AM
Location: Amite, La.
Posts: 367

Hi all: My house went through the great Louisiana flood, and I am just now noticing my never-used oil filled metal-cased Aerovox energy capacitors that were sealed in transparent heat-shrink tubing started to show signs of a small rust-layer between the plastic and metal near the bottom (where the 90 degree bend is in the metal).

I decided to remove this plastic as I noticed some VERY small traces of rust forming between. It seems that they ALL had an oval bottom cut out separately and heat-shrink just inside the bottom of the tubing. These capacitors are oval in cross-section, like an HVAC app. (air conditioner type etc.) I think from the beginning, Aerovox had an idea that the thinness of this metal around the bottom of the perimeter was a bit on the "too-thin" side, but good enough for any normal use!

I have removed the plastic (no writing) and let the bottom ovals fall off. On the worst of them it seems that only a smear of oil (couple of fingertips) was on the bottoms--not nearly enough to form a drop that would fall off!

I think they could be perfectly good if lightly (VERY-lightly surface-cleaned wiped and then dipped to a level just above the bottom "seam" (which all appears to be a solid single piece). The ratings are mostly 196uF @ 2300V dimensions are ~ 1-1/2" TH. x 2-3/4" WD. x 6" HT about 1 pound ea.

The question is: After cleaned and dried: perhaps with emery cloth. WHAT CAN I DIP THE EXPOSED LOWER METAL IN FOR LEAK-PROOFING? I have thought maybe some kind of tar-based thick liquid, but really need help here!! I was even thing of that TV ad---'FLEX-SEAL' or whatever.

THANKS FOR EVERYTHING GUYS!!

Sulaiman

Thu Mar 21 2019, 12:54PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Polyester resin is resistant to vegetable and mineral oils so I'd consider a car repar type of kit;
fibreglass matting, resin, catalyst etc... check your local car repair shop or Amazon or eBay.

The plastic disc at the bottom of the capacitor was probably for electrical insulation/isolation.

MRMILSTAR

Thu Mar 21 2019, 03:42PM

Registered Member #62119 Joined: Sun Feb 04 2018, 04:59AM
Location: Cedar Rapids, Iowa
Posts: 136

I wouldn't encase it in anything. The problem with a sealant is the same as undercoating on a car. If any moisture does happen to find its way under the sealant, it will start rusting and you will never see it until it rusts completely through. I would just thoroughly clean the metal, prime it, and paint it with Rustoleum or something similar. That way if any rust appears you can attend to it immediately and then just repaint it. If you do a good paint job and don't let moisture collect on the surface you shouldn't have any further problems.

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Fri Mar 22 2019, 08:27AM

Registered Member #54278 Joined: Sat Jan 17 2015, 04:42AM
Location: Amite, La.
Posts: 367

...going up the learning curve...I 1st used a very mild action with a circular drill wire stripper--got carried away a bit at the finish (the edge) and noticed a slight film of oil emerging.. I will have to use the very fine steel wool on the edge. That was now! I taped a paper towel with rubber bands and set the cap upside down. Will see how it looks tomorrow. Any suggestions if the film persists on the bottom? It's all shiny clean, BTW. Ready for the Rust-Oleum Primer and paint!? Perhaps ~ three scrubbing, rubbing & quick primer apps will 'overtake' any oil.

MRMILSTAR

Fri Mar 22 2019, 03:09PM

Registered Member #62119 Joined: Sun Feb 04 2018, 04:59AM
Location: Cedar Rapids, Iowa
Posts: 136

Find the source of the leak and apply a small amount of JB Weld or similar 2-part epoxy around the hole in order to seal the leak. I would then prime and paint everything. Obviously, the surface must be completely clean and free from oil before any application of JB Weld, primer, or paint.

Patric

Fri Mar 22 2019, 04:40PM

Registered Member #2899 Joined: Wed Jun 02 2010, 06:31PM
Location: Deinze, Belgium
Posts: 254

I use paraffin.

johnf

Fri Mar 22 2019, 05:28PM

Registered Member #230 Joined: Tue Feb 21 2006, 08:01PM
Location: Gracefield lower Hutt
Posts: 284

i presume the can is tin plated steel
if so just solder it up
if aluminium go withthe jb

MRMILSTAR

Fri Mar 22 2019, 05:59PM

Registered Member #62119 Joined: Sun Feb 04 2018, 04:59AM
Location: Cedar Rapids, Iowa
Posts: 136

Soldering will not work. The oil in the can will act as a heat sink and you will never get the can hot enough to flow solder. Even if you did, the oil will burn and possibly explode. Paraffin will not provide a suitable surface for painting.

If there is still a little oil after your capacitor has been upside down overnight, do the following. Prepare a small amount of JB Weld and have it ready for quick application. With the capacitor still upside down wipe around the leak with some acetone to remove ALL of the oil on the surface. Now, quickly apply some JB Weld to the spot. This will insure that the JB Weld is in contact with an oil-free surface. After the JB Weld cures you can then prime and paint. There are several types of JB Weld. I would use the JB Weld original formula. Another tip would be to place the capacitor in a cooler location for curing even though this increases the curing time. The reason is that you don't want the oil in the capacitor to expand from heat and push out of the hole while the JB Weld is curing which would contaminate the epoxy.

By the way, your experience with the plastic shrink-wrap tubing illustrates perfectly why you shouldn't encapsulate it. Moisture found its way in there somehow, possibly through condensation, and promoted corrosion because there was no way for it to dry out. With the water trapped in there, the metal just rusted away. Because of this mechanism just use enough JB Weld to plug the leak and no more.

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Sat Mar 23 2019, 07:41PM

Registered Member #54278 Joined: Sat Jan 17 2015, 04:42AM
Location: Amite, La.
Posts: 367

Thanks for all the help. I have cleaned and shined the bottom and ~3/4" above that (a label is there I don't want to disturb. I tightly covered the bottom with absorbent paper, and saw no signs of leak (even pressing). The next day, still dry. I just turned the cap upright and when I looked right back under it, I saw a wet spot. The hole on this one is not visible, many are much worse. I plan to dry it all again and use some of the suggestions mentioned. I just bought some Rust-Oleum primer and paint. With the minor leaks, I plan on using the Primer and paint and let dry upside down (with painter's tape covering the rest.
I also got the JB-Weld. I guess I just have to judge how I do the repair. Some caps have become a real mess (but I don't think as bad as it looks--just from being upright. They were all upright on a table which collected a fair amount of oil.
I plan to roughly dry them off, and position them upside down--I think this will stop any of the (slow) leaking.
I sure looks like, with all your suggestions, I will succeed; which means a lot to me. I will post the next observation.
YES, much rust is smeared inside the plastic almost to the top of the capacitors. Does anyone think there is any danger of water inside with the oil?
Thanks much again!!

YES, IT LOOKS LIKE THE PLASTIC WAS FOR INSULATING WITH NO REGUARD TO MOISTURE--WHICH CAN CAUSE SOME REAL DAMAGE.

EDIT:
Maybe i can get the caps dry (when upside down), apply the-JB Weld, make sure I see no moisture leaks when turned upright, and THEN if no leaks appear, apply the Rustoleum primer (let primer dry) and then the paint??

MRMILSTAR

Sat Mar 23 2019, 08:16PM

Registered Member #62119 Joined: Sun Feb 04 2018, 04:59AM
Location: Cedar Rapids, Iowa
Posts: 136

Since it sounds like you are going to rely on the primer and paint by itself to seal some of the tiny leaks, I would find out how resistant your paint is to oil contact. Constant contact with oil may soften the paint. Its probably OK because engine paint doesn't soften even though there may be oil all over it. I know that the epoxy in JB Weld is quite resistant to oil after it has cured.

I wouldn't worry about any minute amount of water that may have gotten inside the caps. When they are upright, any water will sink to the bottom where it will not be in contact with the electrodes.

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