Any special prep required after sandblasting?

[ericher69]

I was wondering if any special prep/work are required after sand blasting and before priming?

In the past priming/painting after blasting has led to rust within a year!

Am I missing a step?

Any advice from pro painters would be appreciated!

Thanks

 

[strum456]

I spray my blasted parts with southern polyurethanes wax and grease remover and wipe them off with a rag. Then i use scotch brite in one hand and an air hose in the oher to blow off the rag fuzzies. Then i spray 2 coats of southern polyurethanes epoxy primer. This holds up very well from my experience.

 

[moored4]

When I bead blast something I take it immediately out using CLEAN gloves and spray it with primer. Clean metal will start rusting the second it's blasted!

 

[strum456]

That flash rust isnt much of an issue. I also try not to let part sit around for a long time but i know a very accomplished restorer that washes his blasted parts with dawn dish soap and water. As soon as everything is dry he sprays epoxy. Of course he gets some rust after doing this and he says it hurts nothing. This guy does very expensive cars that are usually concourse judged.

 

[Gary Fowler]

You just have to remove all the grit from the steel. How you do that is either by washing it with water like a pressure washer or just a water hose or you could blow it off with compressed air but that usually stirs up the dust again. Washing with water is best but then you need to get it dry and immediately prime it. If you are getting rust in a year, I would change paint systems. A good inorganic zinc primer is good as it self heals if scratched and helps prevent rust in light scratches followed by an acrylic enamel top coat should work for you. It could be that you are not covering the sharp edges properly to get proper mils of paint. That is usually a problem with novice painters. I would suggest that you spray all the sharp edges first then overspray them when coating the othe flat surfaces and most of the time this will give you good millage on the corners. See your local paint dealer like Sherwin williams, Dupont or Pittsburg paint suppliers. They usually have a knowledgeable paint person that can recommend a good coating system that will last for many years.

 

[EddieWalker]

You really get what you pay for in primer. I remodel homes for a living and I'm still surprised at how many people use Kilz and then wonder why the paint doesn't go on well, or looks terrible.

Same thing with painting metal. I really like Rustolium Premium paints. They go on better and last a long time without any issues.

As for preping the metal before priming, I just blow off the dust and residue with my air hose and then prime right away.

Eddie

 

[Ductape]

You really get what you pay for in primer. I remodel homes for a living and I'm still surprised at how many people use Kilz and then wonder why the paint doesn't go on well, or looks terrible.

Same thing with painting metal. I really like Rustolium Premium paints. They go on better and last a long time without any issues.



Eddie

Eddie, what do you use when priming woodwork, interior and exterior ? Now that so much has gone water based...... hard to know what works best.

 

[Just Bill]

Look up zinc phosphate metal prep.
Its used for bare metal prep

 

[EddieWalker]

Eddie, what do you use when priming woodwork, interior and exterior ? Now that so much has gone water based...... hard to know what works best.

Zinsser is what I buy. Their 123 primer is great for latex paints and new sheetrock. It's on the shelf right next to the other primers at Home Depot and Lowes. For staines or problem areas, their oil based BIN primer works great, but it's misserable stuff. Sticky, runny, and very strong smelling.

Sherwin Williams brand primers are also very good. They have specialty primers that are just as good, so if I'm at one of their stores, I'll buy their product, but if I'm at the box store, I go for Zinsser.

Eddie

 

[3930dave]

I'm not a pro, so keep that in mind.

For easy to find in Canada, I use Tremclad Red Oxide (oil based) primer. I figure if red oxide is good enough for structural steel.....

Tremclad is an old Canadian label, but I think it is now owned by Rustoleum.

A trick I learned from a bodyman was to use fiberglass resin on problematic seams or weld areas. He'd clean up the area really well, then selectively use the resin to seal these problem areas. The resin will block water from migrating back into the problem spots.

I'm trying a variation of that approach with the steel wheels I just refinished on my trailer. I primed with Tremclad Red Oxide after sandblasting, painted with wheel paint (colour coats, then 2 clear coats). Once it was all dry (next day), I ran a bead of clear silicon around the seam between the inner section and the outer wheel rim, both front side and back. I'll see how this silicon approach stands up over time, as the seams are usually where rust re-starts from.

Rgds, D.

 

[ericher69]

I spray my blasted parts with southern polyurethanes wax and grease remover and wipe them off with a rag. Then i use scotch brite in one hand and an air hose in the oher to blow off the rag fuzzies. Then i spray 2 coats of southern polyurethanes epoxy primer. This holds up very well from my experience.

Sounds expensive! Don't you need supplied air to paint with polyurethanes or does ORganic Vapor cartridges cut it?

 

[strum456]

Sounds expensive! Don't you need supplied air to paint with polyurethanes or does ORganic Vapor cartridges cut it?

With proper ventillation O V cartridges will do. The stuff i use is made by a realitively small.company in georgia. It is probably the best epoxy you can buy for any dollar amount. You will be pleasantly surprised by the price too (unless you are comparing it with something like rustolium). You havent mentioned what you are painting but if it is valuable epoxy is the only product I would consider.

 

[Mace Canute]

I was wondering if any special prep/work are required after sand blasting and before priming?

In the past priming/painting after blasting has led to rust within a year!

Am I missing a step?

Any advice from pro painters would be appreciated!

Thanks

Have a read though this site about "profile".

It's one of the possible reasons for your paint job rusting so soon after it's done.

 

[Renze]

You really get what you pay for in primer. I remodel homes for a living and I'm still surprised at how many people use Kilz and then wonder why the paint doesn't go on well, or looks terrible.

Same thing with painting metal. I really like Rustolium Premium paints. They go on better and last a long time without any issues.

Very true. Some paints are allmost water, they are full of solvents but have no solids in them: When you apply a heavy coat, the solvents evaporate and you stay with a thin layer when dry.

Also if you take the time and money to sandblast, the last 5 bucks on a can of paint means nothing compared to the cost of blasting.
Some primers just eat their way into the metal and stick for decades, and some can be blown off with a pressure washer.

Not all paints/primers are equal....

oh, and to what standard does your blaster blast ?? Swedish standard SA 2.5 is what we demand from our suppliers of wheel loader frames. Sa 2 is enough for earth buckets that wear bare within a day anyways. SA 3 is a 100% equally grey surface colour without ANY impurities, its harder to achieve because the blaster usually works in a dusty environment and cant see his work in bright daylight...

 

[Hooked_on_HP]

Do you have a good water trap on your blaster. If you are useing a siphon blaster you are probably getting a lot of moisture from your air line.Siphon blasters use a lot of air. Pressure tank blasters use a lot less air. If you are blasting when it is cool out you will get a lot of condensation in the air lines. If you paint or prime over moisture it just traps it and makes rust quicker. What media are you blasting with. The coal slag they sell at menards seems to leave a greenish film that I don't like. I still like silica sand. I know you arent suspose to use it but it still gives the best results. You can still get it at menards. The call it handy sand.
Bill

 

[strum456]

I would wager that the last two posts combine explain your problem. You need enough mil thickness to burry the blast profile and and this can be hard to achieve with much of the low solids paint out there. Even if the paint says it is high solids on the can that doesnt mean it is. Unfortunately there is no standard on this and companies are free to market their paint how they want. The only oway to oknow for sure is to buy it and try it.

 

[ericher69]

Very true. Some paints are allmost water, they are full of solvents but have no solids in them: When you apply a heavy coat, the solvents evaporate and you stay with a thin layer when dry.

Also if you take the time and money to sandblast, the last 5 bucks on a can of paint means nothing compared to the cost of blasting.
Some primers just eat their way into the metal and stick for decades, and some can be blown off with a pressure washer.

Not all paints/primers are equal....

oh, and to what standard does your blaster blast ?? Swedish standard SA 2.5 is what we demand from our suppliers of wheel loader frames. Sa 2 is enough for earth buckets that wear bare within a day anyways. SA 3 is a 100% equally grey surface colour without ANY impurities, its harder to achieve because the blaster usually works in a dusty environment and cant see his work in bright daylight...

Standard? For large items I get the local large welding shop to blast

For smaller items I use my blast cabinet with silica free sand from TSC

Yes it is a syphon blaster and I have a desiccant air dryer with a filter after the dryer

 

[EastBerkshireCustoms]

I would suggest a good epoxy primer after blasting with a silica free media. Not only is silica very bad for your health, but it can leave a residue behind that paints won't adhere to.

 

[ericher69]

I would suggest a good epoxy primer after blasting with a silica free media. Not only is silica very bad for your health, but it can leave a residue behind that paints won't adhere to.

Epoxy primer ; any brands in mind?

Are these only available for spray guns or also in rattle cans?

 

[strum456]

What I suggested is epoxy primer. Southern Polyurethanes makes it. Their plant is in Blairsville Georgia. I've used epoxys from several of the major paint companies, and I like the SPI epoxy a lot better. Here are a couple pictures of a paint job I did with SPI products.