TheSamba.com :: View topic - Best treatment for new parts? Bare blasted parts?

Fri Sep 21, 2012 7:00 pm

I am trying to decide how to treat the undersides of the used fenders and the new running boards.

The fenders are rusty now, and so will be blasted down to bare metal.

The new running boards are painted, I am not sure if that is a "cheap" coating intended to only keep it from rusting during shipping or if it is a nice powder coat. We can blast those to bare metal also if that is the way to go.

So the first question is: "Should I remove the black primer on the new parts or scuff that and paint over it?"

Once they are bare, I can think of two basic approaches:

1) have the body shop shoot them with primer and finish paint underneath, then apply undercoat to the finish paint.

--- OR ---

2) Use the 3-step KBS rust seal on the bare, blasted metal underneath, then apply undercoat. Later the body shop would primer and paint the tops as normal.

With either of these approaches, I plan to have the "gravel impact area" at the lower rear section or each fender (~1 foot or so) shot with the "Rhino Hide" truck bed coating. I did not like seeing my beautiful paint ruined by a gravel impact from inside the fender.

I am open to suggestions on the best approach to coat and protect the undersides of the fenders and running boarts.

Fri Sep 21, 2012 7:19 pm

blast anything you want to last, and get it into a coat of epoxy

Sat Sep 22, 2012 7:06 am

skills@eurocarsplus wrote: blast anything you want to last, and get it into a coat of epoxy

X2.

Sat Sep 22, 2012 7:18 am

Can you post a link to some of the "epoxy" I should use?

Does it just go right over the bare, blasted metal? Or is there some kind of primer under the epoxy?

I had assumed that the first thing over the bare metal should be the POR-15 or the KBS Rust Seal. Am I missing something there?

Sat Sep 22, 2012 7:56 am

When they say "epoxy", they are referring to epoxy (2K) primer.

Sat Sep 22, 2012 9:18 am

OK, so would a rattle can aerosol like this:
RUST-OLEUM Aerosol 2K Epoxy Primer, Gray, 13.2 Oz
or this:
Spray Max 2K Epoxy Rust Cure Primer - 3680032
work? Or am I looking for something SERIOUS like this:
GLASURIT 801-704 CV EPOXY PRIMER FILLER CHROMATE FREE

I am getting a real disconnect between all the talk about POR-15/KBS RustSeal and these Epoxy primers. These primers sound like what you would put on the upper (finish) side of the fenders--which I will let my paint shop do.

What I'm looking for is the product and procedure for UNDER the fenders and running boards to protect from the road, gravel, etc.

Can someone help reconcile where the POR-15 type product should be used compared to the Epoxy 2K product?

Thanks in advance for your help.

Sun Sep 23, 2012 5:09 am

I would only use POR15 if there was a lot of rust/pitting. If it is clean metal 2K epoxy is the way to go.

I had my bumpers sandblasted and then put 2 coats of DP90 epoxy on them. Insides of the bumpers are showing rust again after 5 years..

If you aren't worried about color try Macropoxy - black super high-build epoxy from SW

Sun Sep 23, 2012 9:26 am

baxsie wrote: I am getting a real disconnect between all the talk about POR-15/KBS RustSeal and these Epoxy primers. These primers sound like what you would put on the upper (finish) side of the fenders--which I will let my paint shop do.

What I'm looking for is the product and procedure for UNDER the fenders and running boards to protect from the road, gravel, etc.

Thanks in advance for your help.

Yes, what we're talking about IS the same epoxy primer that would be used on the top side of the car. :roll:
I've been using PPG's DP series for over 23 years now, and it's some of the best epoxy primer I've ever used. I use it right after doing ANY sandblasting (used without any reducer), as I want to seal the metal from any moisture that might be in the air, that can cause rust. I've usually only got a 2 hour window before rust starts, due to humidity. I've used it on truck frames, pan bottoms (and tops), under fenders, bottom of truck beds, along the body to pan joints, and engine tins, not to mention the entire top side of the vehicle. The stuff just works like it's supposed to, when applied correctly. 8)

I just don't like por 15, because it doesn't really work (my own experience with it). I've had to re-do so many spots from that stuff, that I don't even bother with it any more. And yes, I used the marine clean, and the metal prep stuff too, and it didn't help. :x I'd try Master Series again if I had to, as it seems to be a better product than the por products. I've never tried the KBS, so I have no experience with it.

Sun Sep 23, 2012 12:32 pm

I was thinking that I was becoming clear on this, but then I see:

ccpalmer wrote: . . . If it is clean metal 2K epoxy is the way to go.

I had my bumpers sandblasted and then put 2 coats of DP90 epoxy on them. Insides of the bumpers are showing rust again after 5 years.

This seems to be an argument AGAINST DP90?

My thoughts were that I could brush (no sprayer yet) on KBS RustSeal (because that is what I have) right over the sandblasted metal.

It looks like all these "2 component epoxy primers" are intended to be sprayed on. If that is the way to do it, I'll have to read up on spray guns and rig up a "priming" spray booth. Or am I missing that I could use a brush?

==================================

Just to be sure . . . a product like this is what I'm after:

SPECTRACRON ® 531/532 High Build 2K Epoxy Primer
A two-component primer recommended for use on properly prepared steel or aluminum where high build and smooth finish are required. Properties include excellent adhesion, toughness and corrosion resistance when blended with QAP532 and QAP532-BLK crosslinkers.

--- OR --- ccpalmer wrote: . . . try Macropoxy - black super high-build epoxy from SW MACROPOXY HS HIGH SOLIDS EPOXY is a VOC compliant epoxy polyamide mastic designed for application to properly prepared steel surfaces. May be used as a one or two coat, direct-to-metal protective coating. Can be applied to marginally prepared surfaces.

Sun Sep 23, 2012 1:23 pm

Don't use POR15 on newly blasted materials. It will work but the best results are on material that is slightly rusted.

Rattle can rustoleum will work fine for your application based upon your description. Make sure you put the most effort, time and care into the prep of the surface.

Tue Sep 25, 2012 4:35 am

baxsie wrote: I was thinking that I was becoming clear on this, but then I see:

ccpalmer wrote: . . . If it is clean metal 2K epoxy is the way to go.

I had my bumpers sandblasted and then put 2 coats of DP90 epoxy on them. Insides of the bumpers are showing rust again after 5 years.

This seems to be an argument AGAINST DP90?

I think in this case the insides of the bumpers were pretty rust-pitted, and while the sandblasting took a lot of it off there was probably some tiny bits of rust left. Two days did go by between blasting and epoxy. And the rust coming back is mostly staining at this point I think...

My current thinking is that if there is any chance any rust is left then POR15 seems to work well. I've only been using it for two years though.

POR15 website says sandblasted metal is fine - key thing is to follow all prep steps -

I love an epoxy but POR15 on my sliding door "step/entry area" is tough as nails - I load tools/wood/etc and the POR15 doesn't budge. Amazing for a one part paint. I also did my sliding door track with it, used the sliding door the next day and a year later the POR15 is rock solid, even where the door sits when shut...

Tue Sep 25, 2012 4:52 am

baxsie wrote: My thoughts were that I could brush (no sprayer yet) on KBS RustSeal (because that is what I have) right over the sandblasted metal.

If using a brush is your desire, I'd go with the Master Series over fresh sand blasted metal. It's primer is self-leveling, and I've found it to be really good stuff.

Wed Sep 26, 2012 11:44 am

There really seem to be a lot of ways to go here.

I went by my local NAPA Automotive Finishes store and talked at length to the very helpful and knowledgeable person there.

The big take-away I got from him is that if I really want long life, I need a "DTM" ( Direct To Metal ) primer. These primers should have the zinc (or other metal) in them that will retard the rust if the outer finish is penetrated.

He sold POR-15, but warned that if the POR-15 is punctured (by sharp flying gravel) that the tiny exposed metal area would then start growing rust. He really stressed that the important thing was to have zinc metal in the primer.

Within the DTM primers there are sandable/no-sand one step/two step and cheap/expensive.

What we decided would probably be the best product for me from NAPA would be the Martin Senour 5227 DTM Epoxy, which is a 2 component, one step process:

http://www.martinsenour-autopaint.com/media/pds/english/MA4702.pdf
http://www.paintdocs.com/msds/PdfDisplay.jsp?docId=43527625
http://www.paintdocs.com/msds/PdfDisplay.jsp?docId=43527624

I'm no expert, but I do see zinc listed on these data sheets, which backs up his claims.

Another possible solution was a two step, using an etching primer then a two component epoxy on top of that. Again he stressed that the important thing was to make sure the etching primer has the zinc in it.

On a separate topic, I mentioned that I wanted to have "Rhino Hyde" shot under the fenders at the gravel impact area. He mentioned that their NAPA store sells a kit for that called "Raptor". It looks like the same thing is here:

http://www.tptools.com/p/2600,186_U-Pol-Raptor-Truck-Bed-Liner-Kit.html
http://www.u-pol.com/documents/datasheets/tds/RLB-TDS-US.pdf

I hope to stop by the PPG store later and ask them the same questions, and also ask the body shop that do the finish painting.

Mon Oct 01, 2012 11:54 am

I contacted a local metal plating shop here in Spokane.

He says he can do "zinc chromate" on the bare blasted parts.

My understanding is that the finish will look like this:

ref: http://www.yellowzincplating.com/FAQ/yellow_zinc_electroplating_information.htm

My plan is to bead blast the four fenders and two running boards and get them dipped.

At this point, my big question is if the automotive finishes will bond to the zinc chromate. At least two source says that paint can be applied successfully over the zinc:
http://www.infinitechfinishing.com/Articles/Article7.htm
http://www.thesamba.com/vw/forum/viewtopic.php?t=529603

Tue Oct 02, 2012 1:20 pm

Rustoleum Rusty Metal primer comes in a brushable can. I refinished my fender under-sides by sanding and wire brushing, using napa rust treatment, wait two days, then brush the Rusty Metal primer on. If you have your hardware store shake the can in the machine, it goes on very smooth. I let it harden for a few days, then used SEM satin black chip gaurd (which is paintable if you want to) on top of that (2 to 3 coats). It also goes on smooth, but not as smooth as paint, more like a modern car wheel-well. The finished look is good, and I think it will be quite durable. It is not rubbery or tarry, and running your hand over it feels like almost a plastic liner. I would do it again, and may use that SEM product on the undersides of my running boards as well.

Another plus is that if a big rock DOES happen to cause a big scrape or chip, I can clean up the damage area and re-spray that chip gaurd on.

Wed Oct 10, 2012 8:14 am

por 15 works GREAT on new blasted metal to protect and prevent rust. follow application on can to the letter and you will not be disappointed. i have por'd many, many, mnay new parts with very long lasting protection. starters, master cylinders, body panels etc... it's pricey but fantastic. only peels if you do not follow instructions and degrease well. acid etching needed if not blasted

Sat Jan 26, 2013 12:17 am

I did some adhesion tests for RustSeal (POR-15 competitor) over here:

http://www.thesamba.com/vw/forum/viewtopic.php?t=5...p;start=25

My conclusions:

* Using a wire brush only, with or without etch does not get a good bond.
* Bead blasting without an etch does not get a good bond.
* We only saw good bonds on the bead blasted, etched samples.

2K epoxy sticks with no etch, even on the zinc chromate.

Sat Jan 26, 2013 12:20 am

skills@eurocarsplus wrote: blast anything you want to last, and get it into a coat of epoxy

really? But can't I spray rattle can on it if I just want to gir'er done?

Epoxy #1. POR15 #2 for me. Rattle can/other #3

Sat Jan 26, 2013 12:23 am

baxsie wrote: I did some adhesion tests for RustSeal (POR-15 competitor) over here:

http://www.thesamba.com/vw/forum/viewtopic.php?t=5...p;start=25

My conclusions:

* Using a wire brush only, with or without etch does not get a good bond.
* Bead blasting without an etch does not get a good bond.
* We only saw good bonds on the bead blasted, etched samples.

2K epoxy sticks with no etch, even on the zinc chromate.

I beg to differ in a way; I agree on #1 - no wire wheels/brushes.

But sandblasted metal + proper prep + POR15 = as good as epoxy or at least very close a screwdriver hit won't chip/nick it. And so far I think POR15 has better resistance to old rust coming back on thick metal.

Sat Jan 26, 2013 10:37 am

ccpalmer wrote: . . . sandblasted metal + proper prep + POR15 . . .
Yes, I agree. This combination was represented by the two successful adhesion tests in blue.

ccpalmer wrote: . . . sandblasted . . .
Point taken.

I now understand that "sharp/angular" abrasive is better than glass beads for paint prep. The sharp abrasive can effectively remove the paint at a lower pressure than the blunt beads.

Less pressure => lighter impacts => less surface relaxation on the metal (it is not heat!) => less warping on thin metal.

One thing that 2K epoxy, POR-15, and RustSeal do not offer is any sacrificial zinc. Once there is a nick that goes through the paint exposing the bare metal, there will be rust. Having zinc on the metal should give at least some "galvanized" style self-healing properties.

I really like the idea of the zinc plated steel, coated with the well-adhered, tough 2K epoxy and a topcoat. (IMHO) I think that has to be close to the ultimate way to battle rust. If only there was a zinc chromate dip large enough for the whole chassis or body :)