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protecting underside of old fenders

3K views 15 replies 6 participants last post by  will's53chevy 
#1 ·
I have cut out the rusted thru areas on my rear fenders and welded in patch panels.The area welded to was thick enough to weld the new patch to but is also corroded a lot, and I am concerned that there may be some pits that could be close to pinholes if left unprotected. Would POR15 and then somthing like rubberized bedliner work good for this, or epoxy primer and then bedliner or undercoat? I am concerned that after it is on the road,stuff off the tires will wreck the fenders from the inside out. What have you guys done in this case. Thanks.
 
#2 ·
It is a common practice on fiberglass fenders to use a spray on bedliner material on the undersides of the fenders. This prevents "stars" from forming from rocks thrown up by the tires. You certainly could do the same on the steel fenders after insuring you have neutralized all the rust.

Vince
 
#3 ·
302 is right, this is getting to be very common practice especially
on fiberglass and SMC fenders.
One caution.
The roll on stuff you see at the discount sores will not do a bit of good as this is nothing more than alkyd enamel with ground up bits of used tire for a texture effect.

Get a two part from your paint jobber but the most important thing is spray it over epoxy.
Reason is, some of these are nothing but thickened up acrylic- urethane and some are thickened up epoxy.
This may sound like I'm contradicting myself here but the thickened epoxy does not have good "shock" adhesion because of the way they thicken it.
The undercoat of epoxy will take care of that problem, and make both kinds at least 50% stronger.
 
#4 ·
Barryk, thanks for the reply. You are suggesting epoxy primer over the metal would be better than POR15. I agree, because this is more of a sealing up issue than a rust killing one. To cover the epoxy, you aresaying to get a quality two part bedliner type product that is compatable with the epoxy. I bought a couple of rattle cans of a bedliner/rockerguard spray to see if it was any good. Srayed it on scrap metal and it dried to a rubbery coating,but thin coat. You would need several coats. You think that that cheap stuff may not stick to the epoxy that well?
 
#5 · (Edited)
Yes it will stick to epoxy, any type of paint well as long as coated within seven days of spraying the epoxy (epoxy has a 7 day open coat) The spray can stuff is nothing more than decorative and will give you no corrosion or protect you from any hard hits.
Any brand of bed liner will stick to the epoxy.

RE: Por
You asked the wrong person for an unbiased opinion.
My answerers will always be based on chemical fact not a general opinion or personal preference.
So I will pass on that one!
 
#6 ·
I had a similar question and wanted to hop in on this thread.

On older cars with lots of sheetmetal...that will sometimes flex and certainly echo tons of noise. I'm wondering if it may be advantageous to use some type of spray-on noise guard like Rockford Fosgate sound stuff...on the undersides of the fenders.
I thought this may help to dampen some of the excess vibration and noise that will undoubtedly happen with such large amounts of metal.

any thoughts?
 
#9 · (Edited)
unstable said:
Barry,

I know you're the man when it comes to this. Do you have any specific recommendations on brands?

Also, if it's spray on, is there any special equipment necessary to spray it? namely a special gun?
++++++++++++++++++++++++++++++++++++++++

I wanted to avoid this type of deal but will try one time:

There are two types of systems High pressure I.E= Rhino, Linex, etc, these are franchise deals and are made of Polyurea
normally heated to area of 175deg and shot with a static mixer with 15,000-50,000lbs pressure.

The other systems are made for the body shops and are epoxy base or urethane base or polyurethanes.
I will list the best brands by "Bracket" If not listed you don't want it.

OK Brands, air dried sprayed with a Undercoating gun. Mixes 1 to 1 or 3:1.

Morton Paint co -(Ohio) - Acrylic Urethane.3:1
Sem - epoxy base. (North Carolina) 1:1
Gator Guard - (Canada) epoxy base 1:1

The above are good and will do a decent job:

The next bracket are the best of the air dried and as close as you can get to the pressure system, won't scratch, resists most chemicals and can be based over and cleared and can be tinted.
These require special guns to shoot, cannot shoot out of a regular
undercoating gun.

Speed liner (Texas) 3:1 mix needs a hopper to spray $65.00
Southern Polyurethanes (GA) 3:1 mix needs Geo gun to spray-$30.
(both the aboves are Polyurethanes.)

Of course the polyurea pressure systems are next.
And the top of list.
 
#11 ·
dragman said:
you shold forget the bed liner and the por 15 and you should sand blast the fender and then imeditly spray techstar on the sand blasted areas(or gavlon but techstar is cheaper and more likley to hold up)
==============================================
Only problem is what they are wanting is sound deadening and something to help stop rocks from underside from damaging the metal or fiberglass.
The above items are some of the best corrosion protecting primers money can buy but won't do a thing for what they are looking for.
 
#12 ·
Thanks again for the great responses.Your last post BarryK sums it up.I'm looking for protection of the fragile origional fender material, which the epoxy will do, then protection from abrasion from stones etc. which the bedliner will do. I am starting to think I should take all four of them to a heavy truck bodyshop I know of that also does spray in bedliners. Having them coat them with the proper spray gun may be better in the long run.
 
#14 ·
BarryK said:
++++++++++++++++++++++++++++++++++++++++

I wanted to avoid this type of deal but will try one time:

There are two types of systems High pressure I.E= Rhino, Linex, etc, these are franchise deals and are made of Polyurea
normally heated to area of 175deg and shot with a static mixer with 15,000-50,000lbs pressure.

The other systems are made for the body shops and are epoxy base or urethane base or polyurethanes.
I will list the best brands by "Bracket" If not listed you don't want it.

OK Brands, air dried sprayed with a Undercoating gun. Mixes 1 to 1 or 3:1.

Morton Paint co -(Ohio) - Acrylic Urethane.3:1
Sem - epoxy base. (North Carolina) 1:1
Gator Guard - (Canada) epoxy base 1:1

The above are good and will do a decent job:

The next bracket are the best of the air dried and as close as you can get to the pressure system, won't scratch, resists most chemicals and can be based over and cleared and can be tinted.
These require special guns to shoot, cannot shoot out of a regular
undercoating gun.

Speed liner (Texas) 3:1 mix needs a hopper to spray $65.00
Southern Polyurethanes (GA) 3:1 mix needs Geo gun to spray-$30.
(both the aboves are Polyurethanes.)

Of course the polyurea pressure systems are next.
And the top of list.
I know that you didn't want to get into this, so I just wanted to ask if the last two products can be purchased by any hotrodder or do you need to be a distributor of some sort.
 
#15 ·
will's53chevy said:
I know that you didn't want to get into this, so I just wanted to ask if the last two products can be purchased by any hot rodder or do you need to be a distributor of some sort.
Both companies will sell to rodder unless, they have a sweetheart deal in a certain area. Than they can direct you.
 
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