Feather edging galvanized panel

[Bob Kontak]

Painting a 944 Turbo. Stripped front three panels as per Freddy Hernandez's paint stripping advice. I left about 1/8 inch paint around all the borders by covering them with duct tape. Freddy knocks this paint off with a DA sander.

99% of the panel is galvanized. If I use a DA sander I will cut through the galvanized coating on the edges. I just want to feather edge the paint where the edges wrap. Is this a hand sanding job, do I have to strip the whole panel or am I just working it too hard and a little burn through is not the end of the world?

I am painting this with Sikkens and will use the Washprimer 1K CF etching primer before urethane primer.

[drcoastline]

Bob,

You will not cut through the galvanizing while feather edging. The paint is much softer then the galvanizing and you will be finished feather edging long before you damage the galvanize coating. Hopefully 962Porsche will chime to confirm but I think 400 paper on your DA you will do the job.

[Bob Kontak]

Good info - I was using 220 on a test spot - too harsh.

[962porsche]

because of the mills of the galvanizing on most porsches is only about 2 mills thick you sand it off real ez . think of it this way it takes about the same amount of effort to sand thru a manila envelope . so just about any amount of sanding on or to bare metal will take some or all the galvanized coating off . so any spot bigger than a quarter you want to spray one to two coats of a chromated E-primer down after sanding . this will replace the galvanized coating . like the Bob's stated try to go with a 320 or 400 grit paper . the finest grit paper you can use is best ! one it will not cut the panel edges and two it will keep as much galvanized coating on the panel as possable . an 1/8 " on the edge is not all that much to feather back with out seeing a gost of the old paint after the car get a new finish on it .so you may be better off to sand the 1/8 " of old paint right off the panels . because you stripped the panels down to bare matel and now you need to prime you will need to have a sand paper cut of about 220 or 180 for the new primer to bite into . if you go with a finner grit cut sand paper than 220 you will get a lower adhesion from the primer or under coats making the finish chip or delaminate very ez . if you did a chemical stripping to the old finish and you have no residual paint left on the panels then you can prep the panels with a red pad insted of sand paper on a DA sander . this will give you the cut needed for a primer to bite into and still leave the galvanized coat intact .

[drcoastline]

I'm glad 962 chimmed in before you took my advice and did damage. I thought the galvy was thicker.

Sorry.

[Bob Kontak]

Porsche962 is a God. Thanks!

It is a mild Catch-22. You want to keep the zinc in place but to prep the surface without stripping the entire panel you have to remove some galvanized material. Even if you use 600 to feather edge.

[962porsche]

O-PLEASE ! i'm no god i have just been doing this body and paint crap for so long . but yes its a catch 22 you need to prep the panel so the primers have some thing to bite into but the grit needed to do so will sand off the galvanized coating real quick . that is why we try to use a red pads . it will give the cut needed to have the primer bite into but it not quight as aggressive as a piece of 220 sand paper . this is just one reason why needless stripping of paint is not good . at times you have to strip the finish off cars because of checked paint . paint that is just so dead that is turned to chalk or the panel has so many chips that you can't feather them out .

[drcoastline]

962- This may be an option for Bob, can you confirm or deny this information?

Last night I was reading the Dec 2010 issue of 911 & Porsche. Page 92 was a write up on Norfolk Premier Coachwork's from the UK.

In the article they are doing some minor rust repairs, road rash fixes and a repaint to a 964. In some areas that meant sanding back to bare metal and that would remove some galvanizing in those areas. The shop states that "modern etch primers do just as good a job of protecting the steel, so nothing to be concerned about". Do you agree?

If so Bob could feather the areas and then etch prime?

Not to high jack Bob's thread but I have a '74 nongalvy car I am not taking the car down to bare metal but I do have some areas that will be taken back to bare metal what do you recommend for metal protection on those areas?

[962porsche]

as i stated you should spray down one or two coats of a chromated E-primer if you have a bare metal spot bigger than a quarter . E-primer is either a epoxy primer or a etch primer . it is very important to only put down the manufacturers recommendations of number of coats of an e-primer . more is not better at all ! as for if a modern etch primer is as good as the galvanized coatings porsche uses ? thats splitting hairs ! there are pros and cons when ever you mess with the OE finish ! but most E-primers of today that are on the market are very good and will equal the the galvanized coatings of todays cars . but ok lets split some hair ! i would not say all E-primers are just as good from brand to brand and will equal the galvanized coatings on todays cars ! i don't know the article you were reading ? so i don't know the primer they are using to make that statement ? but i would say you are more than ok to do any repair down to bare metal as long as you use a activated/catalysed type of a chromated E-primer . another good reason you should use an E-Primer first is that many of the filler primers on the market are not DTM primers ( direct to metal ) . if its not a DTM primer you need an e-primer for the filler primer to bite into to stick to the panel . also not all body fillers stick to galvanized coatings . so you should also make sure that you are using a E-Primer 1st under your body filler if you are not using a body filler that is made to use over galvanized / zink coated metals .

[Bob Kontak]

All good info. I found that if I move the duct tape to the very edge of the panel vs the 1/8" overlap it works well and I can hand sand the feather edge vs taking a DA to it. Still will burn through some but thems the breaks.

I do have to strip the car because of checked paint. The paint was good quality but the build primer was astoundingly thick.

drcoastline - I ended up using the 400 grit to minimize burn through on the 1/8 lip but it still happened.

[Bob Kontak]

Originally Posted by 962porsche

O-PLEASE ! i'm no god

I still love you, man!

[drcoastline]

962Porsche can you give me a little more info on the E-primers? Epoxy vs. Etch? Is one better then the other? Used for different purposes? Stay within the same brand of top coat?

On my 74 non-galvy car which E-primer do you recommend? Epoxy or Etch?

In another thread you gave advice to D911SC who was refinishing his wheel wells. You advised him to use SEM rust-shield to replicate the factory e-coat. Is that the same as the E-primers? if not what gets used where?

Thanks again.