I saw a couple of posts regarding the use of silicone sealer in windshields. The acidic properties of silicone can cause the corrosion which you're trying to avoid. I was told years ago not to use any silicon type RTV for this reason on sheet metal. I was instructed by the engineering dept of a major metal building mfg to use Urethane caulk for this application. Something to think about before pumping it into a windshield frame.
Gary

 

Too late! Already put it on the ss trim around the windsheild. :(

 

:withstupid: :nonod:

 

:withstupid:

 

Well, tell you what, I have used RTV/silicone sealent rubber that smells like vinegar on copper wire for electronics, electricals, automotive, as well as steels of various descriptions over the decades...about 30 years now....

and never had any problems....pull it off years later, even ten years later, and it's on there pretty good, but never a problem sealing a thing, and no corrosion either.....

I think the engineers concern is about the acids in the curing....maybe if the metal is thin enough, but once it cures in about a day or two....the acids are gone and it's about as inert as anything I know of except glass maybe....

MY experiences are all to the positive....

GENE

 

Wouldn't that beat all, I just applied some this past weekend.

 

OH, BTW, it ONLY works on CLEAN metal, no paint, nor grease/oil and NOT RUSTED....obviously.....

You know, my buddy the welder absolutely hates galvenized or cad plated metals....I wonder if something about that plating is used in metal buildings, that will react with RTV......I don't recall ever using it on that sort of metals,....but have used it on many a boat....

GENE

 

Well Gene, can't say for sure about boats I never had one.
Yes, sheet metal roofing is pretty thin and that might be the concern.
I just tossed it out here so some people can think about it.
I have also used RTV for a lot of automobile work without an issue, but will be using urethane when I reinstall the windshield. I believe that's what came from the factory?I htink there are a couple of glassmen here that can answer?
A good test will be when I remove the rear window from my 72 coupe that was siliconed in place 25 years ago!
No flames intended to anyone,just another point of view.
:cheers:
Gary

 

I do know that when I pulled the windshield from my 72, wherever Bubba had tried to seal with RTV the metal was especially corroded.

Course, that may have been cause he never got the leak to stop?
:jester

 

As Gene said. I've been using RTV (732) for years on all types of ferrous metals & aluminum without any problems. It gives off acetic(?) acid when curing so it's probably an "issue" with precision componants, etc, but I can't see a problem with something as beefy as a windshield frame. It's also used by people building yachts.
There are, apparently, types of RTV around that cure without giving off any acid, but I think it'd be a bit OTT to go out & find some. If you think about it, the acid (a weak one) is given off during curing & that's it. But how many people use washing up liquid to wash their cars?? That stuff contains salt & I've dulled freshly bead blasted aluminium castings by washing them with it(much better to use normal hair shampoo if you've not got any car shampoo!).
I heard about the acid "problem" with RTV & the usual scare stories, so I shot blasted pieces of steel & aluminium & then covered parts of them with huge gobs of RTV, along with a piece of stainless & left them outside for a few days(I was bored at the time, OK? :lol: ). When I peeled the RTV off, the metal under it was in a better condition than the rest of it.
:cheers:

 

I use SikaTax / SikaFlex, it's a polyurethane based single compund adhesive that is non corrosive, resistant to water (salt too) and has a limited resistance to oils and grease, no resistance to paint thinners, alcohols and the likes but who uses that on a windshield.

 

The original material for installing our windshields was a butyl rubber
caulking rope. You can still get it - but most glass installers would prefer
to use the more modern urethane sealers to install.

RTV - no thanks. There are lots of single part urethane sealers and adhesives
to choose from. IMO - a better choice unless you need super flexiblility.

BTW - when working at an MIT research lab, we had stockroom access to various
chemicals, etc. They stocked two RTV types : normal and non-corrosive.
Simply from the naming conventions that were chosen, I would go OTT for
the non-corrosive type - if inclined to use it.

:seeya

 

Some RTV's are actually ok to use on metal but you'll need to check the label. I just cleaned out my toolbox at work and pulled out some GE RTV and it states that it is non-corrosive to metal.

 

Well, for years, ever since that stuff came out in the early 70's, thereabout...I been using it on fine wire for elelctrical insulation, and have never seen even the finest BCH copper wire with anything further than surface etching...nothing like corroding....and certainly better than any surrouding exterior connections were....

GENE

 

You are absolutely correct. RTV and metal = trouble. I proved this theory on a Jeep that I had.

This is precisely one of the main reasons Urethane and/or Butyl are used on windshields.

 

The last place I worked manufactured it's own printed circuit boards. They were multi layered surface mount with very fine tracks on them. Any boards that needed modifying/repairing using "cuts & straps" could end up with several fine wires soldered to the tracks on the rear. To prevent the wires snagging on other boards, or the chassis, they were fixed to the rear of the board by using little dabs of RTV. These dabs invariably covered several of the fine copper tracks on the board & in the 10 years I worked there not one problem occured due to tracks being corroded (& being SMT those tracks were incredibly fine).
I've used the same stuff to build several engines over the years & have never had any corrosion problems, even when used on pressed steel chaincases (the difficult part was explaining to the Accounts department why the Software Development team needed so much RTV :lol: ). As proof, if any of you are familiar with Triumph twins you'll know that the pushrod tube oil seals are notoriously difficult to seal. I've been building these engines for 20 years using 732 RTV on those seals. The tubes are chromed steel & the guide blocks are plain steel. The slightest bit of dirt/corrosion will give an oil leak, but I've never had any problems. On engines that hadn't been apart for years the chrome on the tubes that was covered by RTV didn't show the slightest sign of corrosion (& if anything is gonna corrode it'll be your chrome :( ), although the chrome exposed to the outside world is usually dulled/rusted.
I'd use the correct bonding compound if I could get it easily, but I wouldn't worry about using RTV. I've used black RTV on my windshield frame to hold/seal the side window weatherstrip & no corrosion has occured in the 2 years that it's been on there.
Whatever you use, make sure that it is well bonded so that water can't get under it anywhere to form a water trap (that'll rot steel out very quickly).
:cheers:

 

Well, I have experiencd the problem myself, bubba tried to seal the gas tank sending unit with blue RTV, the whole tank was i pristine condition except for under the sending unit flange, a bunch of rust and only where I had peeled the RTV off. I only use black non corrosive RTV on any project.

Marck

 

another example of someone getting information from a questionable source; to where the source sounds very credible... but may only be book smart.

It pays to double-check someone elses "facts". :yesnod: