My 1927 Roadster is going to be out of sandblaster sooner than expected. Monday 10/07/2016 What primer do most people use for heavy pitting and rust prevention? What are you guys using today? What is best ?
PPG DP-90 or whatever their current number is. High dollar paint but good for sealing/preventing rust.
eastwood's black epoxy primer the fill in any pits afterwards with your favorite filler
I recommend PPG's DP-LF primer/ sealer. It's an epoxy sealer that etches to the metal, so you get great corrosion protection. It comes in white (DP40LF),brown (DP48LF), light gray (DP50LF) and black (DP90LF). Doesn't really matter what color for the primary application because you'll prime over it. After it's sealed, you can scuff sand it and use a good body filler to fill in the rust pits. I like 3M Platium Plus filler. It spreads nice, is easy to sand and you don't have an issue with pin holes. After filling the pits, then use a good epoxy or urethane primer to fill in the sand scratches. Direct to metal primer is best even though it's sealed. Finish sand the primer then re-seal when you paint.
I forgot to mention,if you go the (PPG)-DP route, you have a choice of what catalist hardner to use. There's 401 hardner and 402 hardner. 401 requires a 20 minute induction time (which means you mix the sealer and hardner, then you must let it sit in the mixing cup for 20 minutes prior to application). 402 has no induction time and you can mix the sealer and hardner and apply immediately. I would recommend 402 hardner so you don't have to wait for the induction time and just mix and spray. Will not make any difference in corrosion protection for your purposes.
What about Powder coating? after Sand blasting
Can you Powder Coat Nuts & Bolts and Lock Washers and still be able to tighten them
I am asking for a Non T
The DP 90 is also useful to replicate the parkerized finish, but with more rust resistance.
DP adheres better to sandblasted metal without phosphorous treatment, just bare metal--do use degreaser to clean off any oils or sand dust first. After using the filler of your choice, apply a thinned coating of DP 90 (thinned to provide better flow-out and smoother finish) to encapsulate the filler. You can then spray on a surfacer to fill in any sand scratches and then apply the top coats.
Prepared this way, I have seen catalyzed Acrylic Enamel last 20 years out in the weather.
Powder coating is great for wheels and chassis parts. The trouble is, powder coating will not fill in any rust pits, so they will still be there for all to see, and they will show up. You could use a product called "Lab Metal" which is a filler which will take the 400+ degrees to bake the powder coat. I've never personally used it. If asking about powder coating a body, I would never do that. Not only will the rust pits be there, but near impossible to repair, should it be needed. I haven't personally seen anyone do that.
You can get DP60LF also, sort of a blue color. I like all the DP primers, good stuff that lasts and lasts.
Another option along the PPG route is to use their SX1071 Etch Primer direct to bare metal with their ECP17 10-Series Primer for filling and repairs. You can let the etch flash and then spray ECP right over it so the two will "crosslink" which creates a better bond than abrading before spraying and saves a step.
ECP behaves more like urethane primers did. It will cure hard in colder weather whereas DP primers don't "kick" once things get cooler and they continue to move for some time thereafter. ECP also does an excellent job of locking down filler repairs in addition to making it easier to achieve heavy film thickness for blocking out repairs.
We still use DPLF as a sealer over ECP or where we need a true black primer left exposed. It has not been as good a product since they took the lead out (LF = lead free).
When I was ready to have my 26 Touring painted, I took it to Tulsa and had it powder blasted. My painter then sprayed it with aircraft primer, which he said had more body than automotive primers. The paint job turned out great and I was very satisfied. After 35 years it still looks good. Ed
We do need to be clear about Primers and Surfacers, the first is a bonding coating, the second is a filling coating. "Back in the day" they sold a lacquer Primer-Surfacer that did both, although not well, compared to what we have available nowadays.
The DP series (Which, I agree was a better product before it became LF) is a primer. There are other spray products that are surfacers and have a very high solids base to fill imperfections and allow for easy sanding. The ones I used to use are no longer made, so I'm not up on what the types are today (it's been 10 years since I did any automotive painting--although I hope to do some again in the near future). When I was doing painting, I would apply the DP and then within an hour or so, apply the surfacer coating so they would cross-link. And yes, you do have to watch the temperature, DP does not like cool weather--and hates cold weather! IO also failed to mention that once the surfacer is sanded and the surface appears to be ready for finish coating, I apply the thinned DP coat, and then immediately (within an hour or 3) apply the top coat so it bonds to the DP without having to sand it.
Get the MSDS on whatever you use--many of these paint contain deadly stuff that if you don't protect yourself, your health will suffer. Also the manufacture has compatibility and application information, which will help you not do something that will be problematic. I do know the new coatings (they aren't paint anymore) are much less tolerant of contaminants in the material or on the surface than the "old" stuff.
When I was in college I did a special project where I tested corrosion resistance of different coating systems. I made up sample piece of steel, all alike, and applied them with various coating systems. The samples then had identical scratches made to the surface to provide bare metal spots. I then subjected them to a salt-spray bath to induce accelerated exposure. One of the "oddities" I found was the DP had better exposure resistance when applied over bare metal than metal that was treated with a phosphate "Metal Prep." I thought this was an anomaly, and then the new materials handling sheet from PPG came out and it verified my findings!
Yes, sometimes it is wise to read the directions!
A lot of stuff has changed over time. It's almost guaranteed that whatever was used 35 years ago isn't even available today and most of what was around ten years ago, even if the name still exists, is different from what it was back then. At the rate things are going, we will eventually see the day when solvent based primers and paints are regulated out of existence in favor of waterborne, as is already the case in certain states. That will create a whole new problem for the hobbyist unless the technology improves.
David, that's interesting about your findings with epoxy over metal prep as DP isn't recommended to use over etch primer either.
Daniel, PLEASE be sure your blaster knows what they are doing!!!! Sand blasting T sheet metal can cause damage and more problems than you can believe!!!! Putting primer over warped and deformed sheet metal gets you nowhere. I'm sure others can confirm the nightmares on what happens when done incorrectly. Best of luck MG
Thank you guys..... Dan