Phosphoric flashing ??? What's it called!?!

My friend and I were talking about that thing where the spray the stuff on your thing :roll: What is that called? How do you do it?

I am talking about when you sandblast/electrolysis a part and you spray it with the stuff so it doesn't flash rust before you prime it.

Where do you get the supplies and how do you use them?

Any number of products. Some aerosols are in paint bases with the phosphoric acid. Others come in bottles and are dilute solutions of phosphoric acid. Either requires some sort of followup (sanding/scoring, or simply washing off) before getting down to the business of priming and painting. I tend to favor the dilute acid solutions (Ospho, Jasco, and others) that convert the surface metal but leave no residue when cleaned up. That strikes me as preferable to a product with a paint base that might not be compatible with the primers and paints that you want to cover them with.

I've used wd-40 to spray on bare metal.

The product with the highest concentration of phosphoric acid for the money I've found is Behr concrete and masonry etcher sold at home cheapo for about $15 a gallon. You can dilute it down more to what works pour some on and then pour the rest back in the jug.

Scotty has mentioned some and others include evaporust and similar products. According to the msds sheets on those products listed with the epa, the behr stuff has the highest concentration that I have found.

There ought to be a source for pure phosphoric acid by the gallon just like they sell muratic (hydrochloric) acid but I have found it. I'm sure the places that paint and powder coat lots of metal must buy it by the drum somewhere. But then maybe the painters don't use it since it changes the surface of the metal.

This may be the same stuff mentioned earlier. Home Depot sells a Klean Srip product called Phosphoric Prep & Etch. Barr is the manufacturer. It is used full strength for rust stripping. 1 part water to 3 parts Prep & Etch for phosphating. 1 part water to 4 parts Prep & Etch for comncrete etching.

When using it for phosphating, iron phosphate is formed on the surface of the metal which promotes paint adhesion and also thickness. It is important to wash the part well after phosphating to remove residule materials and to thourghly dry the part before painting. The iron phosphate grows on the surface of the metal like little Chritmas trees and really holds water. If dried properly these same growth structures provide a place for the paint to bond. Something like painting a rough sawed board.

I have painted test samples with and without phosphating and can see a difference when scratching the painted surface.

Hope this helps.

Thank You

Thanks ffor the help. It was all very useful. I always get nervous that I won't get all the WD-40 off and I will mess up the paint. I thought I would try this method. There is nothing like playing with dilute acids! It stinks that you will have to scuff or wash it before you can paint. I would hate to wash it, this seems like an invitation for rust. I usually wipe the surface down with solvent before I paint. Will this take care of the coating or is scuffing still necessary?

Must For Rust ($) or Picklex 20 ($$$). Home Depot used to have the former, haven't seen any lately. The latter is available over the internet. A little of each goes a long way and does not have to be washed off. I do remove the residue with a scotchbrite pad. One potential problem. Cast is pourous. If you use it on cast without any further treatment it can get hung up in the pores and later lift the paint. I have used it on cast, but don't anymore. The best way to prevent rust is to keep sandblasted parts in a dry enclosed building. I have kept them for months that way with no other protection. Snow last night, hummidity near 100%. My building is dry, Super A in sandblasted pieces in a couple of piles, they will not rust. As far as electrolysis, etc, which I don't use either -- flash rust will occur immediately, dry the stuff off before it forms and remove what you miss with a wire wheel on an angle grinder or drill and keep it DRY. And no, I don't get condensation with temperature or dew point changes, as mentioned in an earlier post.

Use a wax and grease remover made for the purpose before painting. "Solvents" can be incompatible with the paint. All this info is on the paint and bodywork forum, this site. Hundreds of posts.

(quoted from post at 08:05:30 01/29/10) Use a wax and grease remover made for the purpose before painting. "Solvents" can be incompatible with the paint. All this info is on the paint and bodywork forum, this site. Hundreds of posts.

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Cool deal, I never really went to any of the other forums! I don't like to meet new people

Why don't you like electrolysis?

BTW, we always just put stuff in the shed and it would be fine for a couple of days. In the summer with high humidity you could see little rust spots, but they cleaned right up. We do get condensation formed with extreme temp changes here in WI. The concrete will sweat and so will the steel up here. Not if you keep it in the heated shop.

I am looking at a W-30 with a TRASHED motor that I was thinking about using electolysis on. I have heard it will eat all the rust around the bearings and pistons etc. Both of these machines have been outside uncovered for 30+ years. I have offered the guy scrap price for them and I am hoping he takes it. The investment in these tractors will be HUGE so I don't really want to offer more than that.

We keep seeing this topic. How to preserve steel in the white, blasted, or whatever?
Part of your restoration plan is obviously epoxy priming the tractor. Well why not just plan ahead?
When the items are ready for this extra "preservative" step. why not just use your epoxy primer?
The guy that does my sandblasting gives me a call on his cell before hestarts. By the time he finishes, I am there with a full spray gun. I plug into his air and I have them done, and back on the trailer headed home in about 30 minutes.
So my answer to questions about what to use as an interim coating is, "If you can't prime it when you finish cleaning it, don't clean it. MikeCA learned this the hard way.

Gordo

I don't like or dislike electrolysis, I just have never wanted to use it.

And you are covering all sorts of residual sand, etc with epoxy, particularly on cast. Perhaps it doesn't matter, but I spend more time cleaning the metal after blasting than the operation itself takes.

(quoted from post at 10:27:32 01/29/10) We keep seeing this topic. How to preserve steel in the white, blasted, or whatever?
Part of your restoration plan is obviously epoxy priming the tractor. Well why not just plan ahead?
When the items are ready for this extra "preservative" step. why not just use your epoxy primer?
The guy that does my sandblasting gives me a call on his cell before hestarts. By the time he finishes, I am there with a full spray gun. I plug into his air and I have them done, and back on the trailer headed home in about 30 minutes.
So my answer to questions about what to use as an interim coating is, "If you can't prime it when you finish cleaning it, don't clean it. MikeCA learned this the hard way.

Gordo

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It is kind of weird, we actually were talking about preserving metals that were never to be painted/VERY long term (ie steel in storage). It had nothing to do with tractors or painting or sandblasting. There is a lady on the Miller welding forum that uses it on files and other raw metal tools and that is where the conversation came from. Just kind of wondered what you use more than anything.

(quoted from post at 13:26:15 01/29/10) And you are covering all sorts of residual sand, etc with epoxy, particularly on cast. Perhaps it doesn't matter, but I spend more time cleaning the metal after blasting than the operation itself takes.

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Ditto, I am hoping there is some serious surface prep between the sandblasting and priming.

When I did my rims (the only "real" painting I have done for myself) I painted them immediately. When we did ammonia wagons we have left them inside for a few days with no problems, but that is NOT a nice finish. We would roll really heavy primer and paint on them.

Thanks for all the great discussion!

The only cast items I've had blasted were wheels. I go over those with 4 1/2 angle grinder with 80 grit flap wheels to smooth them up before priming.
The tin, just a healthy dose of 125 air. I don't understand what you have to clean off after sandblasting.
Additionally about 75 % of the area on tin gets body filler or glaze over the epoxy before primer surfacer build starts.

Gordo

Sand is a form of soil, or the slang term "dirt". At a minimum, on sheet metal you should use several applications of wax and grease remover. I wire wheel cast after sandblasting. I simply do not want any contaminant under the paint that I can easily remove.