This question is specifically for those enclosed cavities that do not get opened during a full rustoration. On my car, there aren't many (inner cavities of roof pillars, roll bar, windshield frame, trunk cross member, and inside driver's suspension console). I bought a bunch of tubing to modify a garden pump sprayer so I could spray Ospho/Jasco inside those cavities. My thinking is that it would seep into seams where there is ALWAYS rust even in parts in good condition, and convert whatever rust it contacts. This would be followed by treating with Eastwood Internal Frame Coating, and finally, 3M Cavity Wax Plus. So two questions about the Ospho treatment:

1. Would you do it? It makes sense in my head, but it is spraying acid inside structural components.

2. If you did, would you follow with a water spray to neutralize the acid? My understanding is that the product forms a protective coating that can be left indefinitely, but it needs to be neutralized before it can be painted. For internals, I wonder if I'd get better long-term protection by just spraying Ospho and leaving it alone.

Thoughts?

Sounds like you have a decent plan in place. I used the Eastwood internal conversion/spray coatings and they worked very well. Used several cans and made sure I covered as much as possible

internal spray:

https://www.eastwood.com/eastwood-internal-...oz-aerosol.html

I used eastwood seam sealer as well:

https://www.eastwood.com/ew-brush-on-seam-sealer-quart.html

I wrestled with this question, too with regards to neutralizing the internals after spraying with ospho. In the end I decided that spraying water in areas that I couldn't get to wasn't a good idea. After giving the osphy plenty of time to dry I followed it up with ehammerite or rust-oleum hammered rust cap, (I can't remember which product).

So far so good.

I don't think your supposed to get that stuff on good metal, are you? Wouldn't the frame coating stop the rust that is already present?

Ospho and similar is designed as a metal prep for metal regardless of whether it is rusted. From what I can tell, it etches the metal to provide "tooth" for painting, converts rust to some benign compound that I can't remember, and leaves a protective phosphorous coating to help protect the metal. The data sheet for the PPG epoxy primer I'm using actually says "Chemical treatment or the use of a conversion coang will enhance the adhesion and performance properes of the finished system."


I've had a hard time getting details on how the internal frame coating works. IIRC, they have it listed as an "encapsulator" which suggests it doesn't convert rust by seals it so no oxygen can get to it. That should stop further corrosion IF you get complete coverage. I was thinking of the pre-treatment with Ospho as more of a belts and suspenders approach. First, convert as much rust as I can, then encapsulate. I've also considered spraying epoxy primer instead of internal frame coat using the same modded pump sprayer.

rjames, that is the exact same thought process I'm going through. Water in the internals seems bad, but I wonder if not doing it will interfere with adhesion of coatings. Also wondered if going over all the seems with a heat gun to steam out the water after spraying would be sufficient to dry things quickly.

Ultimately, I think cavity wax is the real hero in the arsenal I plan to use against rust. I've used it before and have been very impressed. Almost 30 years ago, I did a piss poor patch on my pass jack point and sprayed in cavity wax using a homemade application wand. When I opened it up to replace the long on this project, all the places with wax looked pristine even on bare metal, while the rest of the metal had corroded to dust. Now they have wands and have reformulated the product so you get much better coverage. No affiliation, it's just good stuff:


https://www.youtube.com/watch?v=OfisO8h8vYY

Yes I'd use Ospho. No I wouldn't rinse with water.

I use OSPHO and will rinse it on extrernal body parts where I can dry it immediately thereafter. Then epoxy primer. If I use it internally, I make sure that I can drain it and if I can, will also try to rinse it and drain that. If any black oxide remains, I use POR 15 preferably, but also use other spray rust converter or encapsulator, then primer. The internal frame spray primers are sold for the convenience of the hose and spray head that it comes with so you can coat way up inside the longitudinals or even the center tunnel on our cars. I have had very good success with POR15 on floor pans when I remove enough scale and rust powder and follow the directions. It needs topcoat as it is not UV stable.

Some discussions are concerned with remaining acid between layers of metal. If these are re-wetted over the years from rain, this could reactivate the acid and etch or remove more steel. There is merit to this concern. If used, flushing and good drying is needed before rust conversion or sealing with epoxy primer.

Cavity wax appears to be good stuff. I will consider it in the future. Thanks for posting

I have use the Eastwood internal frame coding for several years now and it appears to be working great, super easy to apply but it is runny and will stain anything that it drips onto

The new 3M (old name Minnesota Mining) stuff looks really good. As I said I put a shitload of the Eastwood and rotated it so I know it is all over. There is the question of the heat in the tubes after your car is down the road. The guy says the new stuff does not smell as strong so it must be low VOCs.

I personally do not think you should put metal prep in the longs. If I was to buy your car or say, If you where doing your car for me, I would say pass on the metal prep in the longs and I would be happy with the new 3M waxes but put a lot on with several passes allowing time for drying.

Bob B IMHO

The

I've almost exclusively used Master Series in the past for spraying into cavities. It's less of a rust treatment more of a rust encapsulator / prevent it from growing or spreading. It's a 1K product, moisture cured. It can be thinned and sprayed out of a gun or brushed.

Here's their website: http://www.masterseriesct.com/

It's not cheap at $35-40 per quart, but I've had really good results. I also use it as a primer on top of metal that has been treated or had the rust removed. The entire bottom side of my 914 and some of the trunks or other panels have this as a primer, some places were even top-coated with epoxy on top of this stuff to really keep rust out. It's not as thick or as messy to work with as POR-15 and it won't peel and flake off if you don't apply it exactly as described.

The problem with just using epoxy is that unless you've gotten every last bit of rust pores out of the metal, it will eventually come back. At least with this stuff, I'd like to believe it's truly encapsulated and sealed away.

If you've welded on the longs and need to treat it, I do very hot water with soap, rinse, Ospho (wait 15min), rinse, and then hot water followed with compressed air to dry it out.
I'm a little OCD so I use a heat gun to warm it all up to evaporate the moisture.

Then paint it with whatever product of your choice, and then after it dries you could use the cavity wax if you want. IMHO, once you've restored a car to a certain level, it will probably never see the conditions that brought it to the pre-restoration state.

Let me clarify. The longs on my car have been opened up, rebuilt and the outers replaced. When I had them open, I treated them with metal prep, neutralized with water, then scuffed them with a red scotch brite pad to get rid of the phosphorous residue before wiping with dewaxer and spraying thoroughly with epoxy primer on the internals and Upol copper on the weld flanges. I'm not planning to spray metal prep back inside any of the cavities that have been opened and treated this way (which is most of them). The only thing planned for the longs, tunnel, and other cavities I've had open is to spray with cavity wax, or with internal frame coat followed by cavity wax. Every cavity will be filled with wax to be sure.

But as we know, there is always rust in the seams, even on good panels. It is for those few cavities that are NOT going to be opened that I'm asking. I have the rollbar and roof pillars open enough that I know it is pretty clean inside so I could go either way on the metal prep in there. The area I'm most concerned with is the insides of my driver's side suspension console. The console on the passenger side has been replaced so I treated it like I did the longs. But I know what it looked like in there. The driver's side console is good and solid, but I'd be a fool to think it hasn't started to rust inside. I think every other remaining cavity, I can get a boroscope inside. But that console worries me.

From that website: This will take care of all of your VW rust problems. Good thing we have NARPs or this might not work. Are you using this inside cavities too? If so, how are you applying it?



That's another question I had. I'm using PPG DPLF which is supposed to be a primer and sealer so I am hoping it also seals and encapsulates although I've done a pretty thorogh job of media blasting the cavities I've opened before the metal prep and primer. But it seems like any part that is welded on needs to have some sort of additional coating applied after the welding is done.

I'm currently at a point of using something inside my center tunnel and under the front headlamp assemblies. I've used a product in the past on most of my Brit car restorations called Waxoyl which has an active chemical called CAS-No cosmoline a rust killer. The wax must be the vehicle to help spread and keep it in one place until it solidifies. Only drawback would be in hotter climates the wax would tend to liquefy as the temperature rises. The delivery would be just that to heat it and flow it through an appropriate size spray nozzle.
It worked great!

Then paint it with whatever product of your choice, and then after it dries you could use the cavity wax if you want. IMHO, once you've restored a car to a certain level, it will probably never see the conditions that brought it to the pre-restoration state.
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big time

Bob B

It's ok if it's just me, but water after Opshpo? NO!!! The stuff converts rust, it doesn't keep eating your metal. Please don't add water!!! OMG, it's like yes, I've stopped your rust, now I'm adding rust incubator! Water! Might as well throw some salt down there too. Please don't contribute to the problem. Do not add water after Oshpo. That's about as intelligent as the dingwads who think you need some rust to form before applyling POR15 so it has something to bite to.

It's OK to rinse off Ospho, it's basically phosphoric acid. If you are going to paint it with a rust encapsulating product, you aren't hurting anything., especially if you blow/heat it dry. If you don't it rinse or wipe it off, it leaves a white powdery residue that will inhibit paint adhesion, which is very difficult to wipe off inside the longs and dead air spaces

Milt Becker (Zeke) applied Ospho after patching the hell hole area in the 'BB' and told me to rinse with water and immediately blow the area dry with compressed air the following day. Next was primer and a couple days later the top coat.

I hit the tunnel with the Eastman Internal Frame Coating prior to installing the shift rod & lever, still want to coat the longs at some point. Being on the west coast (CA & AZ), I doubt I'll need anything else (like wax) in the cavities.

I agree. But instead of Ospho I am using this Home Depot stuff which is really affordable. Brush it on or spray bottle even. Several coats over a couple hours. Wire brush where you can reach. Goes black like rust converter. Rinse with water. Immediate compressed air to dry. Heat gun if you are concerned. Hit it with epoxy, acid etch prime, or Por 15 soon. Works for me anyways.
Rich

I'm using the Klean-Strip brand from home depot also. I wound up following this same procedure for the roll bar. Ospho equivalent, rinse, dry, Eastwood frame coating. I'll still follow up the Eastwood with cavity wax in any opening I can access after the welding is done. I agree it isn't necessary, but I've seen firsthand how well the wax works and the Eastwood stuff is still a bit of a question mark IMO. Belts and suspenders.

I'd use a one part rust neutralizing epoxy paint before cavity wax, like Eastwood's Corroless

I'm not familiar with that product. When I search "Corroless" on their web site, their rust encapsulator products show up, which I have used. But I'm not sure how that would get delivered inside the cavities. That's why I've been planning on Eastwood Internal Frame Coating before the cavity wax where possible. But yes, definately some type of rust converter/neutralizer before the cavity wax. Always interested in better products to get the job done.