I installed an Engman kit and am in the process of repairing the jack posts, so I thought I would clean up the inner longs while I'm in there. I had areas of surface rust on the lower edges of the wheel arch sections of the longs that I reached in and wire brushed as well as I could. Then I used a garden sprayer and lightly but generously sprayed in some Marine Clean throughout the longs and rinsed. I had to be careful in the wheel arch sections because there are knockouts that open into the suspension consoles and I did not want any wet stuff to pool up in the consoles. Just to make sure, I blew them out with compressed air after each step in the process. Dried the entire longs with compressed air and my shop vac on exhaust. The shop vac exhaust is great because the motor generates warm dry exhaust air and helps to quickly dry everything up. I let it dry more overnight and used the same spray method with some metal ready, soaked and reapplied, neutralized with a water/baking soda solution, then final rinse with clear water. Dried same as before. Wanted to add some form of protection especially since I just added about 300 welds to the longs installing the Engman kit. I did not want to leave those welds on the inside of the longs exposed to start rusting. Eastwood sent me an e-mail about their new Inner Frame Coating product so I thought I'd give it a shot. It's supposed to leave a zinc phosphate coat to inhibit rust, hopefully it works, it certainly won't hurt, and gives me some piece of mind about those new exposed welds. I bought some 1/8" polyethylene tubing and made up longer spray tubes than the ones included with the Eastwood kit (which are too short to get all the way to the front or rear of the longs from my access point at the jack post). Coverage is good, took three cans for real good coverage with some left that I will use to finish off the inside of my jack post patches. I'll use the seat belt bolt holes, which are almost directly across from the patches, as access to spray the back side of the new patches.
Click to view attachment Driver side wheel arch, shows knockouts that access console
Click to view attachment Passenger side wheel arch
Click to view attachment
Driver side above heater tube. Shadows hide my new welds down the right side, but they are well covered. Final color is a flat olive (army) green.

Wow! You may have a rust free car. Keep the pics for the next owner if you ever sell

It looks good and has to be way better than nothing. I might also use the wax over the phosphate to help against moisture.

That's sweet!

I've often thought about "fogging" some sort of oily or waxy somthing into the longs.

Very nice. Looks like up close and personal on the "914 Cam".

Is there any way to get to the heater tubes (for removal) without cutting metal?

No.

Looks good! I would have been leery about using Marine Clean on inside surfaces, but it sounds like you got it covered.

Looks great! I don't think you'll ever have to worry about them again.