Internal cavity rust treatment, Would/do you use Ospho? Options

[bbrock]

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?

[burton73]

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

[bbrock]

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

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.