Self ethching primer

[marks73]

Hoping early this week to have the media blasting complete on the body and frames. My question is: Self etching primer, then weld in new panels, primer them, then followed by rust bullet? Or, media blast, weld in new panels, self etching primer, rust bullet? Or, media blast, weld in new panels, rust bullet then primer?

Signed,

NEVER DONE THIS TYPE OF WORK BEFORE

 

[KingKong]

Hey, I believe it goes......Media Blast, weld in new panels, wipe down with wax and grease remover, then use metal blast....wait until 100% dry, and 2 coats of Rust Bullet on underbody/wheel wells, engine bay, interior/trunk. On the body you will need to epoxy prime it on bare metal, not rust bullet. Then seam seal everything.

If the blasted metal has been sitting for a while after you welded everything in, you will need to go over it with the D.A. to ensure your coating on fresh metal.

Hope this is right, got all this from reading and seeing ALL of Scott's posts and videos LOLOL.

....Scott's the pro, need him to confirm this.

 

[Qcode351mach]

Hoping early this week to have the media blasting complete on the body and frames. My question is: Self etching primer, then weld in new panels, primer them, then followed by rust bullet? Or, media blast, weld in new panels, self etching primer, rust bullet? Or, media blast, weld in new panels, rust bullet then primer?

Signed,

NEVER DONE THIS TYPE OF WORK BEFORE

DO NOT USE SELF ETCHING PRIMER !!!!!!!!!!!!!!!!!!!!!!!!!! IT SUCKS on a car that has been just media blasted & will provide you NO rust protection what so ever ! Since you may not be working on the car every single day you need a product that will allow you to let the car sit (in between working on it) without worrying about the fresh metal rusting ..self etch is not that product ! You have a choice of 2 products to use to PRIME THE ENTIRE CAR & PARTS BEFORE THEY ARE WELDED IN! after it's been media blasted.. 1 is sikkens ep primer http://www.sikkenscr.com.au/sikkenscr/au/Products/Pages/sikkensprimersurfacerepii.aspx (what I used on mine right after it was media blasted it's the only thing that saved my car when the numnut I gave it to to do the structural work PUT IT OUTSIDE FOR 3 YEARS ! he never ended up doing the work & I pulled the car) Or what I'm using now after we D.A. with 80 grit. which is S.P.I. epoxy 2k http://www.southernpolyurethanes.com/tech%20sheets%20new/2010revised/2010TechManual.pdf The procedure is as follows. After everything is media blasted sand the car & PARTS with 80 grit on the d.a. wipe down with spi water base wax & grease remover WAIT 1 HOUR then prime the entire car & parts with the epoxy (any hidden areas or any areas that are not going to be top coated the same finish as the exterior of the car can then be done in rust bullet i.e. under side of car, the under dash ,inside roof, Those areas I would metal blast (just wipe on then wipe off ,they say use water to remove but I use the spi wax & grease instead. I don't like using water on fresh bare metal ! Once you have a part ready to weld in you remove the primer /rust bullet with a 50 grit disc ONLY where the weld will be..spray the spot where you removed the primer/rust bullet with weld through primer http://www.summitracing.com/parts/TRM-5917 Do your welding grinding then mix a small amount of epoxy primer in a cup & use a foam brush to dab the welded repaired spots or if it's rust bullet do the same. A word of caution when welding around rust bullet DO NOT BREATHE THE VAPORS (it is toxic!!!!) created by the weld areas when welding & keep a air blower handy as of it can & will catch fire.

Scott

 

[marks73]

Perfect. I can do that. Will keep the membership udated on the progress. Thanks Scott!!

 

[PAPPY HAROLD]

IMHO the point here is being missed. When you have bare metal, it often gets contaminants on the surface so you use a metal conditioner to prep the surface in order to get maximum adhesion for your primer. I think if you check that is what your metal blast is. The purpose of self etching primer is that it does its own conditioning and eliminates one step, other than that its primer.... In the past 40 yrs I have even washed the metal with vinegar and water to etch the metal. Now thats old school!! Its the same principal as needed for aluminum painting, No etching and paint falls off. As far as some of the other steps, it seems like alot of unneeded steps and expense to me.

 

[Fordication]

I am still confused about using 80 grit on bare metal. Why so rough if the metal is already ready for primer after blasting and cleaning? I have never seen anyone hit a car with 80 grit before priming.

 

[marks73]

On my last project I thought the same as you. Hear I was trying to get a mirror finish on the bare metal when my neighbor stops over and says " Man that's purty! Hope nothing touches it cause the paint will come right off" It's all about adhesion he said and a rougher surface will hold the primer better. The primer gives you the smoother painting surface while holding the metal. Qcode351 is the best source I've found for any educated explanations though.

 

[Qcode351mach]

IMHO the point here is being missed. When you have bare metal, it often gets contaminants on the surface so you use a metal conditioner to prep the surface in order to get maximum adhesion for your primer. I think if you check that is what your metal blast is. The purpose of self etching primer is that it does its own conditioning and eliminates one step, other than that its primer.... In the past 40 yrs I have even washed the metal with vinegar and water to etch the metal. Now thats old school!! Its the same principal as needed for aluminum painting, No etching and paint falls off. As far as some of the other steps, it seems like alot of unneeded steps and expense to me.

Pappy I agree with your explanation of self etch & you are correct it's primer & that's where the problem lies since ALL primers are POROUS EXCEPT for epoxy primer. Thats why if you don't topcoat epoxy after 7 days you have to sand it & respray. It's also why the epoxy can also be used as a sealer when mixed with 10-50 reducer. Epoxy is not porous! hence no absorption of moisture & no chance for rust to form. I'm sure you have seen cars that have been primered with regular primer or self etch than have never been painted & you see surface rust start to form. When you put a porous primer on bare metal & don't topcoat it immediately it starts to absorb moisture especially if you live where it's humid. Where we used self etch is in a production shop environment where it saves you time..i.e. a new fender job..fender is put on car..goes in the booth..wiped down with wax & grease..self etch applied then topcoat (wet on wet) we did this as a standard procedure all the time. Thats where you use self etch not on a complete that's going to sit for month's or even years till it's painted. I'm totally against using any type of water on bare metal & would rather spend the time & money for a few extra steps to insure peace of mind..There are places where you can "skimp" but buying quality materials & the proper procedures isn't one of those places. Take a look at the spi tech manual..There's also a reason ALL the top builders are doing it per the manual. Pretty shortly everything is going to be waterborne & the change over has already begun..Them old lacquer days and the procedures used with them are a thing of the past. Most shops & builders who are not up on the current technology will fall to the wayside.

I am still confused about using 80 grit on bare metal. Why so rough if the metal is already ready for primer after blasting and cleaning? I have never seen anyone hit a car with 80 grit before priming.

The reason is this..Unless you take the car directly into the booth from the media blaster & prime it flash rust & contamination has already begun. 80 grit on a D.A is not rough at all since the d.a. "oscillates" If you take 80 grit on a grinder it will leave much deeper scratches. you need to know that metal is really clean RIGHT BEFORE you prime. sanding with 80 grit does that & it also provides "tooth" for the product your spraying to bite into. It's also part of the procedure as per the tech manual for spi epoxy (theres a link to that manual in this thread)