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What's the best way to rust proof overlapped pieces of steel?

Started by _woosha_ , Apr 11 2013 12:32 PM

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16 replies to this topic

#1 _woosha_

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Posted 11 April 2013 - 12:32 PM

Can you still paint on kbs between to overlapped pieces that still have to be spot welded together? Eg floor pan to chasis rail lip.

Cheers woosha

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#2 _LS1 Hatch_

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Posted 11 April 2013 - 01:38 PM

What about weld through primer ?

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#3 _Quagmire_

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Posted 11 April 2013 - 01:51 PM

can you weld through kbs?

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#4 UCgazman

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Posted 11 April 2013 - 02:02 PM

I'm using cold galv primer for those areas - more than 90% zinc is ok to weld through (so I've been told, works good so far).

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#5 TerrA LX

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Posted 11 April 2013 - 02:18 PM

And then seam sealer.

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#6 _woosha_

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Posted 11 April 2013 - 02:56 PM

Cheers fella's have been using weld through primer on most repairs, but then I see blokes using kbs or what ever in the same areas. Just confused! I was going to use weld through primer for the repair on my left hand chassis that I'm doing were the crush tube and washer is on the inside of the rail. See "brining another torana to the road" thread, to know what I'm talking about. Do you also have to seam sill every seem on the car?

Cheers woosha

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#7 TerrA LX

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Posted 11 April 2013 - 03:00 PM

Do you also have to seam sill every seem on the car?

Cheers woosha

Seam seal every joint, if you want them water proof.

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#8 jaselx

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Posted 23 April 2013 - 09:52 PM

What is the best seam sealer to use on exterior panels that will be painted? Eg. Top on bottom of rain gutter on a LX hatch.

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#9 jaselx

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Posted 28 April 2013 - 12:56 AM

Sikaflex- is this the best option?

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#10 _mikecatts_

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Posted 28 April 2013 - 05:03 AM

I myself use a combination of Worth weld thru zinc primer and KBS/POR 15.. I sand off where the spot/plug welds go and leave the KBS where no welding is done.. As long as you dont hold the heat its fine....

One thing with the Zinc primer.. It blows back on the first weld.. I tend to scrap away the piant if plug welding and leave for spots... Zinc primer is mainly designed for spot welding.... It does "blow Back" when Mig welding...

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#11 TerrA LX

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Posted 28 April 2013 - 08:11 AM

Silkaflex 221 (or similar) is the best substitute for drip check.

Edited by TerrA LX, 28 April 2013 - 08:11 AM.

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#12 jaselx

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Posted 28 April 2013 - 12:44 PM

sikaflex 227 O.K.?

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#13 tuxedoss

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Posted 28 April 2013 - 10:33 PM

Mike I've also used the wurth weld through primer and as you say it blows back. I've been sprayed with molten metal a few times. I'm not sure it's actually that weld through as they state. As you said I find if your plug welding its best to scrape off the primer around the hole and then there is not as much splatter and swearing.

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#14 _mikecatts_

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Posted 29 April 2013 - 04:10 AM

It does work very well when spot welding.... I found the copper based weldthrough primer does the same, but not as bad when "plug" welding.. Dont know about corrosive ressitance though.. I tend to stick to the Worth brand,, being Zinc based..and its an epoxy paint as well...

To stop blow back..I use a 2mm step drill and drill through both panels,, Making sure nonly to get the 2mm bit through the bottom lip.. Makes it easier and no blow back as it blows through the 2mm hole..

Mike I've also used the wurth weld through primer and as you say it blows back. I've been sprayed with molten metal a few times. I'm not sure it's actually that weld through as they state. As you said I find if your plug welding its best to scrape off the primer around the hole and then there is not as much splatter and swearing.

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#15 TerrA LX

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Posted 29 April 2013 - 01:10 PM

sikaflex 227 O.K.?
[/quote

AFIK yes, as long as it is specified for joint fixing and sealing and is sandable and paintable.

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#16 _LH SLR 3300_

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Posted 02 May 2013 - 09:05 PM

Weld thru primer is generally designed as a protective coating for bare steel on spot welded panels as it is conductive for the spot welder electrode tips, therefore doesn't inhibit the spot welder from doing it's job. Of course it can be used for the same purpose for MIG welding but as MIG will burn off any substrate more so than high frequency spot welding, it isn't a guarantee against future corrosion. In the course of repairing previously accident damaged cars i've found rust around MIG welds on panels that have been coated in weld thru primer, not so much spot welded panels. Usually this is more evident on panels that have been poorly sealed or not sealed at all. A rule of thumb I've taught myself is to be extra vigilant in sealing any panels that have been MIG welded, the MIG welding changes the molecular structure of mild steel making it more prone to rust that raw or spot welded steel. Learning about metallurgy is an important part of panel beating, you can be placing people's lives in your hands when repairing badly accident damaged cars & can be held liable if someone is injured or killed due to or in part to your workmanship. As for sealing panel joins, i don't generally use Sikaflex as a sealer because I've found that paint will crack & or delaminate over time on urethane adhesive/sealers, especially if it is applied more than a slight skim. I use seam sealer such asTeroson, it is very similar to new car sealer & is designed to be over painted. I seal every panel join on my cars, I've learned the hard way after doing a few repaints/restos for myself by finding rusty stains around door skin folds etc after washing the car a couple of times or parking in the rain. All above is just my opinion based on 20 years experience in smash repair & vehicle restoration business.