Little test with Rust-o-lium "Cold galvanize compound" and weld thru primer. - Hot Rod Forum : Hotrodders Bulletin Board
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Old 02-12-2010, 11:39 AM
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Little test with Rust-oleum" Cold galvanize compound" and weld thru primer.

Deadbodyman brought up this cold galvanizing compound a while ago in the "body gurus" thread.

I have to say first off, DBM says he uses it with Osphro an acid etcher, I did not! Let me make that clear, I used it as most anyone would not being DBM. I sanded the metal with a da and 180 grit paper before I primed it. It covered RIGHT NOW! I mean, RIGHT THE F NOW this stuff covers like ten coats with ONE!

Edit: I did just notice something looking at the photo, it says on the Rust-oleum, it is for "repair" of galvanized metal.





But as I suspected (again, this is WITHOUT the Osphro) it didn't stick worth a crap! You can see here how I scraped it off EASILY with my finger nail. Even with the weld thru (though this is "Etch/weld thru") held on with just a tiny bit coming off the metal. The Rust-oleum came off without so much as a whimper of a fight with my nail.



I then clamped it together and plug welded them together. The Rust-oleum didn't weld nearly as nice as the weld thru, for ME. I may be able to do just fine after a little practice, this was ONE weld. But it seemed like I was welding with a contamination.

Neither held up very well to the clamping. Now, mind you, they had dried for DAYS. Both applied to DA sanded surfaces!

The scraping you see is from clamping them, yes, but mostly from twisting the two pieces of metal apart to test the weld.





You can see that they both burn right around the weld about the same.

But without a doubt, these products should be used JUST at the weld point. This is why the recommendations for weld thru primers have changed so much in the last few years. People have been WAY over using them in collision repair. JUST at the weld point is the only place they should be. The rest of the seam and interior of the part should be ecoat or epoxy.

Brian

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Old 02-12-2010, 01:27 PM
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You were able to twist them apart? To test the actual weld quality did you count the number of times you had to twist on each piecebefore it came apart?LOL,I warned you three lights coats that comes out awfully heavy(surprised me too)....and It does come off but not that ez when I did it.they look they BOTH scratched pretty easy... but like I said with the Ospho for rust protection and better adhesion the price of 6.00 a can is well worth using it,compared to the cost of epoxy primer and prep and dry time its not The best way but a good enough way I also said If I want something to last a long long time I use epoxy and for the inside of two rocker halves its perfect (no one will be getting in there and scraping it off)...what are the ingredients in the weld thru primer and what was the cost?I'm told the ingredients are the same and still don't know....But IT do weld thru ,do it not?....it didnt all burn off around the weld much ether.. your weld looks great BTW... come on over ,I got a few thousand more you can do.. Oh ,now try not scratching it and leaving it outside to see how long it takes to start rusting .and if you really want a shock try treating bare metal with ospho and leave that outside and last ,two more pieces one treated with and scratched and one treated and not scratched I've done all of these....The results were very surprising.... Of coarse you'll need a bare piece of the same steel as a control....One more thing Brian...does the weld thru burn look a lot bigger than the galvinizing compound or is it me? DAMMMMM, you gots some purdy fingers.So ,on a scale of 1-10 how would rate them each?and will you try it again?

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Old 02-12-2010, 01:37 PM
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Good Test

Hey Brian, Good test and good photos too. I've still got some repair to do on my truck that will be concealed, some I'm following with interest. Comment on the repair to galvanized metal statement. I've used similar cold galvanize on the job to paint the welds on galvanized angle, channel,etc. When you spray in on with the metal still warm, it bakes on nicely. Even sprayed cold, once it finally dries it'll stay there for years, even in a corrosive chemical plant environment. olnolan
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Old 02-12-2010, 01:57 PM
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THAT REMINDS ME.....Brian, try to scratch the burnt part to see how well THAT sticks...I never tried that and always wanted too..I suspect from my welds that I left outside that it sticks even better because only the unprotected weld got any rust ,nothing around the burnt compound.
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Old 02-12-2010, 09:24 PM
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How many times you twist it means nothing. If the "weld nugget" pulls from the metal, it was welded properly. I do have to say that I have done these tests before and had forgotten how hard it is to twist the weld loose. I had to beat on the friggin thing with a hammer back and forth to break it!

I have to say that the cold galvanize came off REAL easy, MUCH, MUCH easier than the weld thru primer. With no effort what so ever it came off with my finger nail. Yes, where they were beat up twisting them apart they look similar. But I am convinced beyond any doubt that it has VERY POOR adhesion properties. One thing I just notices while looking at the photo of the can is the "For the REPAIR of galvanized steel" with the "Repair" in bold print, interesting.

I just went out and did the scratch test on the area surrounding the weld. Interesting in that on the cold galvanizing spray the area right at the weld almost seemed to hang on SLIGHTLY better than the area outside the weld area! While the weld thru primer was just the opposite! My nail scratched of the weld thru primer in that "whitish" ring around the weld and STOPPED immediately as I went out onto the primer. While the cold galvanizing hung on tiny bit better in that "whitish" area and immediately scraped to bare metal the second I left that area.

By the way, I applied two coats of each product. The cold galvanizing looked covered in one coat without a problem. Maybe one coat would be enough?

But personally, I see no need to use it and I won't. But it was interesting.

Brian
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Old 02-12-2010, 09:32 PM
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If you like those welds, check out this thread. Example of a student of mine welding.

Brian
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Old 02-13-2010, 05:42 AM
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Arnt kids great? so ready to learn new things,I hope you let that little girl run with it you might have a real artist there.your boys got a bright future also...I'm looking foward to my two yr old grand daughter hanging around the shop she seams very interested in cars...Right now she makes me nervous I cant take my eyes off her for a second.....
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Old 02-13-2010, 06:11 AM
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In the '70's and '80's I was using RM zinc phosphate primer at the first coat on new parts. For example, on like a rocker panel that was going to be hidden after welding I would thoroughly paint the panel, even the flanges, and use it as a weld thru primer. This stuff had extremely good rust resistance, and I felt it worked very well as a weld thru primer as well.

Anybody else use either zinc chromate or zinc phosphate primers like this in the pre-epoxy days?
Anybody know of a source for these primers today? All I can find is in an aerosol can.
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Old 02-13-2010, 07:17 AM
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Quote:
Originally Posted by rdupree
In the '70's and '80's I was using RM zinc phosphate primer at the first coat on new parts. For example, on like a rocker panel that was going to be hidden after welding I would thoroughly paint the panel, even the flanges, and use it as a weld thru primer. This stuff had extremely good rust resistance, and I felt it worked very well as a weld thru primer as well.

Anybody else use either zinc chromate or zinc phosphate primers like this in the pre-epoxy days?
Anybody know of a source for these primers today? All I can find is in an aerosol can.
Thats exactly how I use this stuff,OR I'll epoxy at great expense....after seeing how poorly it stuck to bare metal,I used Ospho before applying this for much better adhesion and rust protection BUT it doesn't stick as well as epoxy ,not by a long shot.
But then again it doesn't need too, even undercoating scrapes right off if you can get in there. For top dollar jobs epoxy is the only way to go BUT if the money just isn't there (as in my case) this is a great alternative my budget minded customers think so too.I only get a couple high dollar jobs a year the rest are people with limited cash for their toys..........Brian, I also agree with you on not having a need for it.there's only two ways to repair collision work ...with used sheet metal or with new sheet metal in BOTH cases they are already coated .....On the other hand repair panels for the very old cars (pre 60's I'd say) Come un coated or are hand made and in BOTH cases they need SOMETHING for protection before welding them together You cant weld raw steel and expect it to last any amount of time (not over here anyways)...SO ,I'll wrap it all up by saying ....IMO,there's only two ways to weld repair panels together,go all the way with epoxy primer or this way a great alternative at very little cost ...never weld two raw steel panels together and expect it to last.there may be better low buck alternatives but this the best I"VE found.It's only to be used for hidden ,hard to get at panels (like two rocker halves) OR to protect exterior panels from rust if left outside BUT, it has to be removed from exterior panels before any further work begins...
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Old 02-14-2010, 08:07 AM
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Brian,
thanks for doing the test....
proves the product data sheet I posted on the previous thread is correct:

there are next to no "binders" in the mix on that particular brand to promote "bond and adhesion"...

my $.02:
"replenish" the zinc supply with the Rustoleum (on a chain link fence whatever) rather than "repair" could have been a better word on the label

for it to work to fight galvanic corrosion,,,the zinc itself does have to be in "intimate" contact with the steel so minumum binders possible is the smart choice..

Last edited by red65mustang; 02-14-2010 at 08:33 AM.
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Old 02-14-2010, 08:51 AM
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As I said In that post ,My painter hooked me up with it,I wouldn't use it(I always used epoxy) and he actually brought it to the shop...thats when I tried it so he gets the gold star,I'm just passing it on ....even WITH the ospho, it scratches off..if used in the concealed places as mentioned it works just fine ....I like it, and will keep on using it for certain jobs since I make my own patch panels...it will NOT work well inside wheel wells or floor bottoms etc....strictly for bare steel that cant be reached after welding is done.It does NOT take the place of a good epoxy primer ...it only costs about 6.00 a can way cheaper than weld thru primer...just to be clear...

Last edited by deadbodyman; 02-14-2010 at 09:12 AM.
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Old 02-14-2010, 09:09 AM
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BTW,Brian, doing one weld????? thats kinda like eating one Lays potayo chip isn't it???? or one M&M.....
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Old 02-14-2010, 11:07 AM
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Quote:
Originally Posted by deadbodyman
BTW,Brian, doing one weld????? thats kinda like eating one Lays potayo chip isn't it???? or one M&M.....
It was hard, but that is a standard American Welding Society plug weld test. Simply weld two pieces together with one weld and twist them apart.

I would imagine any amounts of welds chiseled apart would show you the same thing though.

Brian
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Old 02-15-2010, 07:10 AM
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Brian,
did some reading and found there are dozens of "Industrial" cold galvanizing coatings brands (that do meet mil spec and ASTM test standards) that are virtually the same zinc-epoxy contents as the Rustoleum TDC....

they all call for "sandblasted" surface (= about a 60-80 grit?) texture on their TDS which would create more bond surface area to grab versus the 180 grit you used....
and none call for and kind of acid {oxalic/phosphoric/hydroflouric/etc} surface prep treatment

they all warn the surface must be absolutely dry/low humidity to get decent adhesion...

I'm adding this to the thread because "rough and dry" is easy to do for those that want to use a cold galvanize coating

I actually went looking to see if I could find one with just a bit more binder for adhesion (give up just "some" sacrificial anode action for better bond),,no luck...
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