What are your thoughts about using Non-Corrosive RTV Silicone Sealant?

[aweir]

I am looking for a way to seal my enclosure joints and a subwoofer gasket, and I read everywhere that regular silicone sealant releases acetic acid during the curing process and that this is bad for speaker components.

I came across a tube of Locktite non corrosive silicone sealant but it's quite expensive.

Unfortunately non corrosive sealant is not sold in any stores for whatever the reason.

The only thing close to that is DAP flexible solvent-based sealant which appears to not be silicone-based.

My last resort is to use Duck rope caulk for the subwoofer gasket but I'm not sure how well it would hold up as a sealant caulk for joints.

 

[TLS Guy]

Don't use RTV silicone. That is for working on engines and machines.

This is what you need.

It will not harm speaker parts. A thin layer will work fine. You must be prepared to get your fingers dirty!

 

[aweir]

TLS Guy, that sealant looks very similar to DAP Alex Plus Latex plus Silicone sealant which is also what people recommend using. https://www.homedepot.com/p/DAP-Alex-Plus-10-1-oz-White-Acrylic-Latex-Caulk-Plus-Silicone-18103/100097524

Would you recommend either one? People also say use a urethane sealant which doesn't contain any silicone at all such as Sikaflex or polyurethane construction adhesive.

 

[Johnny2Bad]

As long as it's latex formula (look for "paintable", that's one characteristic of latex) you should be OK.

3M sells silicone based sealants / adhesives specifically designed for electronics, but you probably don't want to pay what it costs. 3M is a vendor I trust to not screw it up, you don't want to find out five years down the road you used the wrong stuff.

I don't see a real need for something like the 3M product if it's speakers you are working on; if you were maybe wanting to adhere a capacitor to a PCB or component enclosure it's the right stuff to use if you need silicone benefits (heat capacity, for example).

Lots of people use one of the "Goop" products, but I haven't looked very hard into them so just as an FYI rather than a recommendation.

If you're trying to make a gasket that is remove-able, use some kind of release agent on both or one surface. If one surface your adhesive/sealant will adhere to the other surface.

Spray wax works good (mask the areas you don't want the spray to go) or a finger dipped in vaseline if you don't mind a little staining on untreated or plain stained wood (painted is OK) or can keep it off areas that will be visible.

If you use the paintable latex, it usually only comes in limited colours, none of which are particularly attractive (white or brown, sometimes clear, basically). A soft scraper (maybe a silicone kitchen spatula, although I just use a margarine tub lid cut carefully in the width I need and straight across with scissors) wetted with water will make cleanup or tooling squeezed material easy; use the empty tub of margarine with water and dip your tool into it to work the adhesive as required. Only needed if your latex adhesive squeezes out of your gasket area and would be visible and bothersome.

Note: if you don't use latex-based adhesive/sealant, don't use water. Only latex-based product is water-soluable.

 

[MrBoat]

For a speaker gasket on the cabinet side, it can be cured before fastening the driver as long as it's just thick enough. Why not just use weather tape? For the joints in a speaker cabinet, unless the joints are extremely rough, the adhesive used to build them suffices as well. Wood glue, for example, remains somewhat pliable after cure.

 

[TLS Guy]

TLS Guy, that sealant looks very similar to DAP Alex Plus Latex plus Silicone sealant which is also what people recommend using. https://www.homedepot.com/p/DAP-Alex-Plus-10-1-oz-White-Acrylic-Latex-Caulk-Plus-Silicone-18103/100097524

Would you recommend either one? People also say use a urethane sealant which doesn't contain any silicone at all such as Sikaflex or polyurethane construction adhesive.

Either one will be just fine. No mental masturbation required!

 

[aweir]

After mulling around in the store today I came across some Flex Shot rubberized sealant. I believe this will be the closest thing to a speaker gasket as you can get. I decided to stick with the Alex Fast Dry for the inside joints.

https://www.walmart.com/ip/As-Seen-on-TV-Flex-Shot-Rubber-Sealant/36259390?action=product_interest&action_type=title&beacon_version=1.0.2&bucket_id=irsbucketdefault&client_guid=0bb7b1aa-84f2-4256-3778-83b190acec36&config_id=2&customer_id_enc&findingMethod=p13n&guid=0bb7b1aa-84f2-4256-3778-83b190acec36&item_id=36259390&parent_anchor_item_id=36259395&parent_item_id=36259395&placement_id=irs-2-m2&reporter=recommendations&source=new_site&strategy=PWVUB&visitor_id=YWda5vf8OQ8KtmjxqCQXYE

 

[lovinthehd]

I just used plenty of wood glue and speaker gasket/weather stripping for the driver....no leakage issues.

 

[Swerd]

I am looking for a way to seal my enclosure joints and a subwoofer gasket, and I read everywhere that regular silicone sealant releases acetic acid during the curing process and that this is bad for speaker components.

As others said above, there are several types of inexpensive sealants or caulks that work to seal enclosure joints, make gaskets, or attach and seal port tubes.

I'd like to address the often repeated warning to avoid RTV (room temperature vulcanizing) silicone sealant because it releases acetic acid. Although it is true that this does contain acetic acid which does evaporate as it cures, it is not at all true that this is bad for speaker components.

This is an old wives tale, often repeated over the internet. I believe it is repeated by people who have little or no understanding of acid-base chemistry. They simply see RED when they read the word "acid". I have spent an entire career as a biochemistry scientist (over 30 years in the lab). I do know what acids and bases are, how they act, and which ones are and are not strong and corrosive. The acetic acid that evaporates from RTV silicone is harmless. Acetic acid is a weak acid, there is too little to start with in uncured RTV silicone, and it evaporates soon enough to be no problem at all.

On another audio forum, I once read about a test that measured how much acetic acid was contained in uncured RTV silicone and how much remained over time as it cured.

https://analyzeinc.com/success-stories/acetic-acid-release-during-silicone-rtv-cure/

The uncured sample (zero time point) had 23-24 µg acetate per mg of RTV silicone. After curing for various times, 0.5 to 4 hours, the amount of acetate fell to about 2 µg/mg or lower. While the majority of the acetic acid was rapidly lost from the silicone, there is still about 0.4% of the available acetic acid remaining after three days of cure.

In other words, about 99.6% was gone by that time.

If you use RTV silicone in a speaker cabinet you are building, seal it before installing the drivers and crossover board. Allow it to cure overnight, you will have no problems at all.

If that isn't enough for superstitious or irrational readers, there are plenty of inexpensive options available.

 

[aweir]

The acetic acid that evaporates from RTV silicone is harmless. Acetic acid is a weak acid, there is too little to start with in uncured RTV silicone, and it evaporates soon enough to be no problem at all.

Enlighten us further. Is there a difference between the amount of acetic acid released from RTV silicone vs. the typical silicone bathroom/kitchen caulk? If acetic acid is nothing to worry about, why do they sell this non corrosive silicone caulk?

Anyway I went with the Flex Seal in a can. Yeah its messy but I think it gives better coverage.
Wood glue might provide a good enough seal, but wood glue is not intended to be used as a sealant since it shrinks as it dries.

 

[Swerd]

Is there a difference between the amount of acetic acid released from RTV silicone vs. the typical silicone bathroom/kitchen caulk?

As far as I know, RTV silicone is the same as the typical 100% silicone bathroom/kitchen caulk.

If acetic acid is nothing to worry about, why do they sell this non corrosive silicone caulk?

I don't know. But there must be some applications where solvents other than acetic acid are needed, or they wouldn't make it. I do know that DIY speaker building is not one of them.

Anyway I went with the Flex Seal in a can. Yeah its messy but I think it gives better coverage.
Wood glue might provide a good enough seal, but wood glue is not intended to be used as a sealant since it shrinks as it dries.

As long as it remains flexible and seals, its getting the job done. No one else will see the inside of the cabinet .

Those are big cabinets. Subwoofer?

 

[aweir]

Yes, it's for the Stereo Integrity HT 18 V.2 Subwoofer kit that I'm building.

 

[slipperybidness]

I am looking for a way to seal my enclosure joints and a subwoofer gasket, and I read everywhere that regular silicone sealant releases acetic acid during the curing process and that this is bad for speaker components.

I came across a tube of Locktite non corrosive silicone sealant but it's quite expensive.

Unfortunately non corrosive sealant is not sold in any stores for whatever the reason.

The only thing close to that is DAP flexible solvent-based sealant which appears to not be silicone-based.

My last resort is to use Duck rope caulk for the subwoofer gasket but I'm not sure how well it would hold up as a sealant caulk for joints.

Seems that I may be late to the party, but this is the stuff that I use:
https://www.amazon.com/gp/product/B005T8R6LY/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

I like this stuff very much, I use it for many other applications now too, simply because it is a robust product, and it does not have the offending odor like several other products do. Personally, I prefer to avoid the (corrosive) RTV materials for my electronics projects, especially considering that I may be using some of these materials directly on PCBs to help hold down very delicate connections with tiny wires inside gaming controllers, etc. If you need a less robust material, often hot-glue (i.e. thermo-melt plastic glue) can be a good alternative.

@Swerd
You also make some very valid points. I will also mention, many of these products that contain Acetic Acid (or may contain formic acid as an alternative), will often contain ammonium too, another somewhat corrosive material. The SDS may not even list the ammonium.

Remember, I am a chemist by trade and I work in the semiconductor labs. I have personally done this exact type of testing to produce that type of data that you provided! You make a valid point, if you can't find the non-corrosive material, then let the RTV cure overnight to limit the exposure. We often take that same approach, apply the material outside the factory and let it cure before we take it into the factory.

I'm the sentry to decide what materials get used in the factory freely, what materials should be limited, and what materials should not even come into the building!

 

[Swerd]

@slipperybidness

Thanks for your comments. Yes, I do remember that you are a chemist and work in the semiconductor manufacturing world.

You provide a good answer to the OP's question about why the more expensive non-corrosive RTV silicone is made. In an electronics factory there are good reasons for using non-corrosive RTV silicone instead of the much less expensive acetate-emitting kind. You will be using lots of it (Why stock two types?), a large factory can negotiate a lower price, and it eliminates the possibility of an employee using the wrong type of silicone.

 

[highfigh]

Holy glue-up, Batman! I have never seen building a box over-though to this extent.

Use wood glue for the joints. A flexible sealant will cause the joints to fail under extreme stress. If the goal is to make a durable, inert cabinet, use some kind of mechanical fastener along the joint, too. If the glue doesn't fill the gaps, THEN, use a sealant. Any sealant. If you use silicone, wait until it no longer smells like vinegar before installing the drivers- problem solved. Otherwise, use latex caulk but DO NOT use it to attach the joints- it WILL fail.

In the 20+ years I spend working with car audio, I saw only a couple of box joint failures and they were all caused by the customer ignoring the advice that they not crank the system until the next day, at the earliest. One guy drove off and before he even got to the street, we could hear that his system was cranked and, as we told him, the joints failed. Wood glue and pallet staples work really well for this, but not before the glue dries. I have built boxes of particle board, which is the 'hot dog' of lumber products and when I dropped one of them on a concrete floor, it just bounced.

 

[lovinthehd]

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Anyway I went with the Flex Seal in a can. Yeah its messy but I think it gives better coverage.
Wood glue might provide a good enough seal, but wood glue is not intended to be used as a sealant since it shrinks as it dries.

With the cnc/dado cut flatpack you're using, a good gluing up should be quite sufficient. Maybe if you had some sloppy cuts and gaps of your own to deal with...maybe sealant might be needed....or just more glue along the seams afterwards.