after blasting ?

[bodyman]

iv ebeen doing this along time but never really been comfortable about what to do to bare metal after blasting it . ive used ppg products for years all of the metal conditioning products have to be put on then rinsed with water ive never liked the ideal of putting water over bare metal !!!! does anyone make a bare metal conditioner that safe to leave unprimed or painted for a while ? and safe to prime or paint without water rinsed or striped again ? i put alot of hours in my paint jobs & would hate to redo because rust issues coming up later ??? thanks

[Alchemist]

Blasted metal parts do not require a "metal conditioner" but a good direct to metal (DTM) primer to prevent oxidation (rust). Be sure to blow/wipe off residual powder/dust from the parts (using a oil/moisture trap at the base of the air blower) prior to priming.

PPG's DP/LF Epoxy primer is a good product and other manufacturers have comparable products.

Take a look at this product. I've been using this for a long time and works great for restoration projects.

www.zerorust.com

Hope this helps!

Alchemist

[bodyman]

yae but where im at the humidity can be really high. sometimes i cant get the car blasted & in epoxy the same day this happened on the dash of a car im doing the paint blistered in a small area about three months after i painted it . sure enough there was rust under the paint !! i used dp 90 on it ,then k201,then dbc base coat , 2001 clear. the compressor air was checked by my paint supplier and said it was clean and dry ?? wore gloves never touched the metal with bare skin ,so what gives ??? im hoping the rest of the car doesnt give me any problems its not been painted yet.

[Alchemist]

bodyman,

I've mentioned this in another thread so, pardon me if you are already informed but many users who apply DP epoxy primer, apply one or two wets coats then allow to flash and then surfacer etc.,

Epoxy primers as well as other products require a minimum DFT "dry flim build" in order to meet minimum service requirements.

I too shared the same experience with DP epoxy primer many years ago, with the popping from substrate corrosion. I only applied 2-3 wet coats of DP and went on to apply surfacer etc.. at that time.

In my experience 3-5 mils of DFT using epoxy primer is what I've discovered to prevent moisture bleeding. Anything less and you can/will see blistering with corrosion under the epoxy primer. So, depending on how you apply your material, will dictate how many passes or coats you need to meet this requirement. Obviously, 2-3 wets coats will not be sufficient since, in general, when solvents evaporate, depending on the product sprayed, in this case DP epoxy primer, leaves approximately a 50% DFT - so a hypothetical deduction would be 6-8 coats of DP to meet the minimum standard requirements and to allow for sanding/scuffing of the DP prior to applying surfacer. I highly suggest you allow the DP to dry at least 7 days because this is the amount of time required for DP epoxy primer to fully crosslink (cure) and if the temp remains consistantly around 70-75 degress ambient. Any deviation of temp, especially lower temperatures would require additional dry time.

Epoxy primers will seal out moisture, but require, as I've already mentioned a minimum DFT.

PPG's K201 or any primer surfacer for that matter is porous and will not prevent moisture from bleeding to the substrate.

Again, this is from my experience.

[Denvervet]

Is it safe to assume that you use a wax and grease remover with adequate drying time prior to appying the DP primer?

[bodyman]

Is it safe to assume that you use a wax and grease remover with adequate drying time prior to appying the DP primer?

yes . i only put 2 coats of dp allowed the proper time ( i dont remeber but i think the tech sheets claimed 1 hr )before i put the k 201 on then allowed the k201 a couple of days to cure. sanded pre cleaned then painted . i thought the tech sheets said not to do more than 2 medium wet coats ? maybe that was my problem?? maybe moisture from the outside air ? maybe someone bumped into the bare metal with there skin .thats why i was asking about conditioning the bare metal first . i dont know where i went wrong ? ive been a painter in the collision repair business for over 18 yrs but doing cars from bare metal up is a totally different animal . when i talk with my ppg rep i really dont get any real world feed back just what the tech sheets say . they are pretty much geared for the collision rpr market in my opinion . thanks for any and all help

[David Sloan]

yes . i only put 2 coats of dp allowed the proper time ( i dont remeber but i think the tech sheets claimed 1 hr )before i put the k 201 on then allowed the k201 a couple of days to cure. sanded pre cleaned then painted . i thought the tech sheets said not to do more than 2 medium wet coats ? maybe that was my problem?? maybe moisture from the outside air ? maybe someone bumped into the bare metal with there skin .thats why i was asking about conditioning the bare metal first . i dont know where i went wrong ? ive been a painter in the collision repair business for over 18 yrs but doing cars from bare metal up is a totally different animal . when i talk with my ppg rep i really dont get any real world feed back just what the tech sheets say . they are pretty much geared for the collision rpr market in my opinion . thanks for any and all help

Go to SouthernPolyurethanes.com
They make primers an paints that are for the restoration ind.
We love the MS clear, it stays looking wet longer than anything eles i have used.
Check out Barrys Paint's an info. they also have a forum an you want find any better customer service than they give.

[Alchemist]

bodyman,

From my experience, if anyone had touched the blasted metal part with bare hands and left for a few days, I would see corrosion in the shape of finger or a palm. Quite annoying - LOL!!

I've been in the restoration arena for over 25 years and I never have the opportunity to prime blasted parts immediately. So, my procedure is to take the blasted part and buzz over it with a clean and strip disc or bristle disc initially. I make sure the panel look "shiny everywhere". This procedure will convert the blasted part from the "bead blasted" look to a smooth shiny swirly like finish. This will remove any surface corrosion from ambient contamination or from being handled with bare hands.

At this point I wipe the part down with a good wax and grease remover. Afterwards, blowing across the part, not on it, my air blower having a moisture trap attached to it, wiping it with a good clean towel. As I've mentioned in another thread, I like the Scott Blue Shop Towels. Don't use the shop towels that are sent out and chemically cleaned by a service. These are good if you are doing mechanical work but a disaster if you use them for prepping parts for paint. I tell you this from personal, painstaking experience!!

For the final step, I use a DA or orbital sander with an #80 grit sandpaper disc and abrad the entire part so that there is no evidence of shiny metal.

Now the part is ready for DTM primer then surface etc.,

As for PPG's DP epoxy primer - the tech sheet is specifically directed for air quality compliance and towards the collision repair industry - not for restoration, which is why the tech sheet will read that you apply 2 coats prior to topcoating.

Even if you applied a metal conditioner and the chemical leaves a conversion film on the metal, you would still need to prep the part appropriately prior to coating with any paint materials.

I can appreciate your situation because I've had to address the same issues more than a few times. I still "scratch my head" in wonder because when you restore something from the ground up, it's very difficult to keep every part clean or away from interested hands, unless you have a vaulted surgical facility - LOL!!!!

Now, that's an idea - huh?!!!

Hope this helps!

Alchemist

[bodyman]

alchemist & everyone else thanks for your help. alchemist i did it exactly the way you described bristle disc , then 80 grit da wiped it down with the blue paper towels & all!?!? its just one of those things i guess ill never know where it went wrong ??? hopefully the rest of the car will be fine ?? thanks again for all your help