Internal Frame Coating/Cavity Wax Question
 

I am trying to treat some of the rust on my 220D. For internal cavities where access will not be possible after the rust repair, which is a better treatment:
1) a zinc phosphate coating like this:
Internal Frame Coating w/Spray Nozzle | Eastwood
or
2) a yellow cavity wax type coating like this:
Heavy-Duty Anti-Rust in Amber - Rust Proofing Products - Eastwood

I am not committed to Eastwood necessarily, as many others make similar products. But am just trying to figure out the best approach to preventing further rust on internal cavities. I have seen both types of products recommended here in DD, so am a bit confused how to proceed. Thanks.

I like their internal frame coating. first link. I've used it on all my repairs that required that type of protection.

I'd use it again.

Oddly enough, I've never used Eastwood's internal frame coating, but I swear by their heavy duty anti-rust. I will be using it inside my rockers, post-repair.

Hmmm, one vote for each. Clear as mud, as they say. haha. I do appreciate the advice.

Here is a pic down the rocker/sill of our one 300SD. I sprayed some of the internal frame coating down it, not a complete spray it looks like.
http://www.peachparts.com/shopforum/3284000-post3.html

Additional pics you might find useful:
W124 300D Rust Repair 7-20-13 - Imgur

300SD Rust Analysis ~2 Years Later - Imgur

Here is another option. I've never tried it but it's an interesting read.

Home made Waxoil

Have a look around light aircraft parts sites ( Aircraft Spruce , Sky Geek and so on . ) I seem to remember an oil made for closed spaces that wicked. ( Though I'm sure a roll or two would help the process as well. )

Linseed oil might be a possibility.

Avoid the zinc in acid suspension rust treatments for cavities. So stuff like POR15 metal ready is a no no in my opinion partly because you can not wash the surface effectively but also because if you do wash the surface all you are likely to do is to put water between unprotected spot welded joints...

...I have heard talk of how "acid dipped" restorations have had a lot of trouble later on because the acid wasn't washed away properly. Think of the area around a battery tray for example and then think of that inside your rockers / sills.


My choice of product would depend on the condition of the area you are treating. If it has already been treated at some point in its life with a cavity wax then applying a paint-like treatment won't work. Paint doesn't stick to grease. In this case I would go for something like Dinitrol cavity wax.

If it is virginal very very very little surface rust then a paint system would probably work. However with even light surface rust - no matter what it says on the tin (i.e. don't believe the paint straight over rust claims) - a paint will peel off. Peeling paint inside a cavity makes the application of a wax a bit hit and miss - so you mess up your future treatment chances.

I think that generally speaking a decent cavity wax with rust inhibitors is probably going to be best. But you can over cook it and put too much in a cavity. If you do this and you clog up the drains then you end up with an emulsion that aids corrosion (think water in an automatic transmission - eeek!)

There's another product called fluid film or something like that, uses lanoline to coat the internal frame bits, and seems to be very effective, as it seems to be popular in marine applications.

Thanks everyone for all the great suggestions. Based on the fact that I am trying to protect existing metal that is not virgin, nor easily cleaned, my plan is to use a oily spray called CorrosionX HD (heavy duty). It seems similar to the second Eastwood product I linked to above. The reviews on amazon are very positive:
http://www.amazon.com/Corrosion-X-90104-Heavy-Duty-12oz/dp/B0009H1AMG/
It is a thicker version of this product, which also has good reviews:
http://www.amazon.com/CorrosionX-Lubricant-Penetrant-aerosol-90102/dp/B0009E1QWI/ref=cm_cr_pr_product_top
It is sold by both of the aircraft sites that 97SL320 mentioned above, which is where I learned of it. So thanks again for all the help.

Stretch nailed it. On an old car, you have no idea of what you are trying to treat, nor any way of preparing the surface.

I used Fluid Film insome areas as well as Krown and Rustcheck sprays. Latter two are the most common rust treatments most of us use each year in Canada.

Most of these products need to be done regularly. No magic potions ;)

Cheers mate!