Author Topic: Adhesive or Sealant to make aluminium casing waterproof  (Read 2173 times)

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Offline EEVaditya

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Adhesive or Sealant to make aluminium casing waterproof
« on: June 28, 2018, 06:12:41 am »
Hello,

I have a electronic control unit which has got aluminium casing.

Kindly suggest a product which will joint  the aluminium casing and its aluminium lid (metal to metal) thereby making it water, oil and dust proof.
 

Online BradC

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Re: Adhesive or Sealant to make aluminium casing waterproof
« Reply #1 on: June 28, 2018, 06:28:24 am »
A gasket?

I've had terrible experience long-term with adhesives on Aluminium unless they are applied with the proper prep (ie break down the oxide layer in an inert atmosphere and ensure a good adhesive coverage to ensure bonding to the metal and not the oxide). Of course if it's not thermally sensitive then either an aluminium solder/braze or preferably a TIG to weld it shut.
 

Offline OE2WHP

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Re: Adhesive or Sealant to make aluminium casing waterproof
« Reply #2 on: June 28, 2018, 07:11:10 am »
What's wrong with bonding the sealant to the aluminium oxide layer?

Thanks
 

Offline EEVaditya

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Re: Adhesive or Sealant to make aluminium casing waterproof
« Reply #3 on: June 28, 2018, 10:12:40 am »
I want sealant or adhesive which will cure at room temperature.

which will bond, seal the two aluminium parts together.
and can withstand with the moderate temperatures (not too low not too high)

I just want to make the unit waterproof.

I have seen some sealants which are grey in color, and somewhat elastic rubber type when gets cured so those type of.

 

Offline d-smes

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Re: Adhesive or Sealant to make aluminium casing waterproof
« Reply #4 on: June 28, 2018, 10:27:49 am »
Do take note that when you seal the enclosure to keep water out, you are also sealing water vapor inside the enclosure.  As atmospheric pressure and temperature change, you may end up with condensation on your electronics.
You may wish to purge and seal with or in an inert gas or include a desiccant (drying agent) within the enclosure.
 

Online BradC

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Re: Adhesive or Sealant to make aluminium casing waterproof
« Reply #5 on: June 28, 2018, 10:44:42 am »
What's wrong with bonding the sealant to the aluminium oxide layer?

Long term it has a tendency to come off. Unless the oxide layer is formed by hard anodizing, it tends to be extremely fine and brittle. Not a problem in day to day use as any that comes away immediately re-forms, but if it has glue stuck to it when it comes away then the glue stays stuck to the oxide which is no longer attached to the underlying metal.
 

Offline OE2WHP

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Re: Adhesive or Sealant to make aluminium casing waterproof
« Reply #6 on: June 28, 2018, 11:58:20 am »
Interesting. We never had issues with that yet we did not use the sealant as a glue but just as a sealant and screwed the lid to the housing.
Another thing to consider is temerature related pressure differences. You might want to use a  pressure compensation membrane.
 

Offline David Hess

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Re: Adhesive or Sealant to make aluminium casing waterproof
« Reply #7 on: June 28, 2018, 02:12:55 pm »
I have heard of JB Weld epoxy being used for this sort of thing but it would not be my first choice.  Some epoxies will bond very well with aluminum:

https://www.amazon.com/Loctite-Hysol-gram-Epoxy-Adhesive/dp/B000WXDLAQ
https://www.miller-stephenson.com/product/ms-907-two-part-epoxy-adhesive/

3M has a bunch of similar industrial epoxies which would be easier to use in a production environment but only one for aluminum:

https://www.3m.com/3M/en_US/company-us/all-3m-products/~/3M-Scotch-Weld-Epoxy-Adhesive-DP420NS/?N=5002385+8710979+8713609+3293241657&rt=rud

Could you cut a channel in the walls or lid for a neoprene o-ring?
« Last Edit: June 28, 2018, 02:37:11 pm by David Hess »
 

Offline stj

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Re: Adhesive or Sealant to make aluminium casing waterproof
« Reply #8 on: June 28, 2018, 05:21:32 pm »
rtv silicone,

or a car product called blue hylamar (probably spelt wrong)
it is a liquid gasket for aluminium heads and water pumps.
you put it on and fit the part loosely.
after it sets to a rubber you tighten the part against it - used by rolls royce.
 

Offline T3sl4co1l

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Re: Adhesive or Sealant to make aluminium casing waterproof
« Reply #9 on: June 28, 2018, 07:52:43 pm »
If you don't need water immersion protection, it would probably do well enough to heavily grease the joint.  Use a thick, high temperature grease.  Not, like, vaseline, which would run off at elevated temperature.

A gasket would be preferable for maintenance purposes.

If "permanent" sealing is acceptable, then an RTV silicone rubber will do.  DO NOT use corrosive (acetic or amine based) formulas!

Tim
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Electronic design, from concept to prototype.
Bringing a project to life?  Send me a message!
 

Offline CopperCone

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Re: Adhesive or Sealant to make aluminium casing waterproof
« Reply #10 on: June 29, 2018, 04:49:16 pm »
If you want a really good seal then just solder it with whatever the aluminum version of staybrite is. You can take it apart with a torch. It smells like complete shit though.

Steel solders really well, aluminum is a bit harder. The steel flux might be fairly corrosive though.

Might want to coat both sides, clean very well, abrade then join without additional flux. Might be tricky.
« Last Edit: June 29, 2018, 04:52:29 pm by CopperCone »
 

Offline xavkno

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Re: Adhesive or Sealant to make aluminium casing waterproof
« Reply #11 on: June 29, 2018, 10:07:54 pm »
Maybe a good first question would be: what do you want to store in the aluminium casing?
 

Offline jtronix

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Re: Adhesive or Sealant to make aluminium casing waterproof
« Reply #12 on: July 02, 2018, 05:31:06 am »
@EEVaditya I think you want a solution for Electronic Control Unit (ECU) casing and cover fixture (shown in attached image) so that water or any other liquid solution won't enter inside the casing, like Engine Control unit.

I think liquid gasket can be used.

Not sure whether it last for a long period.

@stj have you ever try rtv silicone for electronic casing?
« Last Edit: July 02, 2018, 05:47:22 am by jtronix »
 

Offline stj

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Re: Adhesive or Sealant to make aluminium casing waterproof
« Reply #13 on: July 02, 2018, 10:35:40 am »
yes, i have tried rtv in the past to seal masthead antenna amplifiers after repair.

just make sure the surfaces are clean and buy neutral cure stuff.
it comes in 3 types, acid cure, alkaline cure, and neutral cure.
 

Online sotos

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Re: Adhesive or Sealant to make aluminium casing waterproof
« Reply #14 on: July 02, 2018, 11:23:27 am »
yes, i have tried rtv in the past to seal masthead antenna amplifiers after repair.

just make sure the surfaces are clean and buy neutral cure stuff.
it comes in 3 types, acid cure, alkaline cure, and neutral cure.

Does it come of easily if you want to repair it ?
 

Offline stj

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Re: Adhesive or Sealant to make aluminium casing waterproof
« Reply #15 on: July 02, 2018, 09:25:05 pm »
depends on how porous the surfaces are, but you can clean it off with a scraper or flat screwdriver.
 

Online nctnico

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Re: Adhesive or Sealant to make aluminium casing waterproof
« Reply #16 on: July 03, 2018, 12:00:42 am »
If it doesn't need to be submerged: don't make it water or airtight. You can't. You'll always get water vapour inside which then condenses. A better approach is to conformal coat the circuit boards and make sure water can escape from the enclosure. Besides the water vapour condensing a small leak won't get the electronics wet and the water can still get out.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline EEVaditya

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Re: Adhesive or Sealant to make aluminium casing waterproof
« Reply #17 on: July 04, 2018, 12:24:32 pm »
@jtronix, yes I exactly need the same.

any suggestions for neutral cure rtv silicone sealant or gasket makers.
 

Offline stj

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Re: Adhesive or Sealant to make aluminium casing waterproof
« Reply #18 on: July 04, 2018, 04:26:27 pm »
rtv is used in the building trade to seal baths and sinks to the tilling - go look in diy centers.
it comes in big 300-400ml cartridges for beer money.

example:
https://www.everbuild.co.uk/product/450-builders-silicone/
 

Offline EEVaditya

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Re: Adhesive or Sealant to make aluminium casing waterproof
« Reply #19 on: July 05, 2018, 06:42:45 am »
My application is in the automotive sector.

The surface will be metal. any rtv silicone sealant or gasketing product? or liquid gasket maker?

different people use different terminologies.
 

Offline stj

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Re: Adhesive or Sealant to make aluminium casing waterproof
« Reply #20 on: July 05, 2018, 09:49:03 am »
read the datasheet at that link - metal or glass etc. no problem.
 

Offline Wirehead

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Re: Adhesive or Sealant to make aluminium casing waterproof
« Reply #21 on: July 10, 2018, 06:39:28 am »
Do take note that when you seal the enclosure to keep water out, you are also sealing water vapor inside the enclosure.  As atmospheric pressure and temperature change, you may end up with condensation on your electronics.
You may wish to purge and seal with or in an inert gas or include a desiccant (drying agent) within the enclosure.

This can't be stressed enough. Many underestimate this. Maybe it's better for the user to encapsulate it (and put it on a vibrating plate to get the air bubbles out.)
"to remain static is to lose ground"
 

Offline EEVaditya

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Re: Adhesive or Sealant to make aluminium casing waterproof
« Reply #22 on: July 11, 2018, 10:17:17 am »
working on some rtv silicone gasket maker (neutral cure). but any more suggestions and recommendations are always welcomed.
 

Offline jtronix

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Re: Adhesive or Sealant to make aluminium casing waterproof
« Reply #23 on: July 13, 2018, 04:57:04 am »
what happen to aluminum body if sealant is used other than natural cure?
 

Offline JonM

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Re: Adhesive or Sealant to make aluminium casing waterproof
« Reply #24 on: July 13, 2018, 05:49:37 am »
"Regular" RTV produces acetic acid during curing:

 https://code541.gsfc.nasa.gov/Uploads_materials_tips_PDFs/TIP%20044R.pdf

Here are some details about Aluminium and acetic acid:

 http://www.electrochemsci.org/papers/vol9/91005496.pdf

When I thought of these issues, I was more concerned about the effect of acetic acid on the electronics and soldering (not sure if it is valid...).

I have an un-opened tube of American Sealants #388 neutral cure silicone standing by for some future application. The rest of my silicone sealant stock is "marine grade" and probably emit acetic acid during curing.

 http://www.americansealantsinc.com/388-electronic-grade-silicone/


 


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