Rust prevention

[Treeman]

Originally Posted by marcedesbenz

Government trying to save money?

Is this an oxymoron?

[GGR]

Hi all,

I'm pleased to find this thread. I've been using POR-15 on various parts and though I did not use them yet results look good: restored a fuel tank, painted a rear axle and a manual transmission after rebuilding them, and will soon paint a rebuilt front axle. I've been using one coat of semi-gloss black POR-15 and then one coat of Chassis Coat Black also produced by POR-15. I will treat the underside of my '62 W111 Coupe when I swap all my rebuilt items. The car is very sound and does not need any rust repairs. Just some surface rust here and there that needs brushing and prepping before applying POR 15.

My question to all the specialists here is how best to proceed. I'm planning to clean well all the underside, and then brush the surface rust and any coating not holding well, but I won't remove what is still holding tight. I was first planning to coat everything with POR-15 but I was told it is not necessary on areas where metal is not bare. What do you think? Wouldn't coating everything be an additional protection? Or would that be wasted money and energy? What about "Chassis Coat Black"? I would prefer coating all the underside for aesthetic reasons but will it hold on areas where POR-15 wasn't applied?

Thanks in advance!

[Graham]

Originally Posted by GGR

My question to all the specialists here is how best to proceed. I'm planning to clean well all the underside, and then brush the surface rust and any coating not holding well, but I won't remove what is still holding tight. I was first planning to coat everything with POR-15 but I was told it is not necessary on areas where metal is not bare. What do you think? Wouldn't coating everything be an additional protection? Or would that be wasted money and energy? What about "Chassis Coat Black"? I would prefer coating all the underside for aesthetic reasons but will it hold on areas where POR-15 wasn't applied?

Thanks in advance!

Most Benzes have some type of rubberized coating on the underside. It is quite thick and sometimes rust develops behind the coating.

On my old cars, I have looked for spots where that coating is loose or bubbled and cut them back to metal. Then applied POR-15 then an undercoating spray from an autoparts store. It eventually all blemds in.

To strip off all the old undercoating would be quite a chore. But if it was done and then POR-15 applied followed by Chassis black that would do an excellent job! I suspect that you could apply Chassis black or any black undercoating spray over the existing undercoating just to spruce it up. Try some in a small area first.

I first used POR-15 back in 1989 on my '72 SLs trunk sump and that job is still good as new. Great stuff!

[GGR]

Thanks Graham,

I don't have that rubberized stuff under my car, just paint. I don't know if it was removed or if it was not there on early models.

[Graham]

Originally Posted by GGR

Thanks Graham,

I don't have that rubberized stuff under my car, just paint. I don't know if it was removed or if it was not there on early models.

That's a big plus!

I was at a local car show recently and spoke to some guys with Model A and T Fords - They were into POR-15 and had painted the entire chassis with it and then overcoated with black chassis paint.

The great thing about POR is that it gets so hard and is unlikely to chip and develop weak spots. The overcoating chassis paints are really just cosmetic.

But it's really a case of cost and how long you want it to look good. Eventually it all gets covered with road grime anyway

[GGR]

So I can just coat POR-15 over the paint there and it will hold and protect efficiently?

[Stretch]

Originally Posted by GGR

So I can just coat POR-15 over the paint there and it will hold and protect efficiently?

POR15 have a de-greaser called Marine clean. I think you should use this at the very least. It is water based and they say it won't kill fishes (if that floats your boat) - but importantly for your car it doesn't leave a residue that could react with your first coat of POR15.

KBS another company make a similar range that I have been using - as well as the POR15 stuff.

Both of these companies have a water based de-greaser Aqua clean is the KBS version. They then also have pre-treatment stuff - the KBS one is called rust blast. It essentially adds a zinc layer on top of the rust and turns the surface black. They say the more you soak the more rust you turn into hard black stuff. I think this works well - though it is a pain in the arse applying it the the underside of a car (it drips off!).

POR15 and KBS Rust seal seems very similar in the pot / can - though I get the impression that POR15 adheres and covers better than the KBS product.

Both companies have top coating products that are flexible enough to paint on to suspension springs - so they say.

I've just done my car - underside + front and rear suspension in a combination of KBS and POR15 products so in a few months / years (hopefully) I'll be able to say what works best.

My final comment is that there doesn't seem to be too much of a difference between these products - I bet they share the same (or similar) patents.

[Stretch]

Oh yeah both companies (POR15 and KBS) also have a primer that allows you to paint "normal" paint on top too

[Graham]

Originally Posted by GGR

So I can just coat POR-15 over the paint there and it will hold and protect efficiently?

From my experience, POR-15 will stick to most surfaces, but painting it over existing paint doesn't make much sense because for one, it is expensive and then you are relying on the existing paint for adhesion to the steel. Your idea to use POR where you have bare metal, and then overcoat entire bottom with a Chassis paint, is probably the way to go. But don't worry if you get some POR onto existing paint.

Just out of interest, how will you get at the underside - Will you have it up on a hoist?

[GGR]

Thanks Army and Graham,

I will brush and clean all the uderside, then apply Marine Clean, rince, apply Metal Ready, rince and apply POR-15 in the relevant areas. I will then apply chassis black coat everywhere. It-s not going to be a fun job though as the only installation I have are four jack stands.

[Graham]

Originally Posted by GGR

Thanks Army and Graham,

I will brush and clean all the uderside, then apply Marine Clean, rince, apply Metal Ready, rince and apply POR-15 in the relevant areas. I will then apply chassis black coat everywhere. It-s not going to be a fun job though as the only installation I have are four jack stands.

You need one of these

[Stretch]

Originally Posted by Graham

You need one of these

I think we BOTH need something like that...

Read the warnings that come on the tins

For example

"If Rust Seal dries on your skin only time will remove it"

They do mean it.

[GGR]

Originally Posted by Graham

You need one of these

Waow! Indeed, what is that called? Where can I get one?

[Stretch]

Originally Posted by GGR

Waow! Indeed, what is that called? Where can I get one?

There are loads of versions of these available

see

http://www.cjautos.org.uk/phdi/p1.nsf/supppages/cjautos?opendocument&part=2

for example or search for "car roller" / "chassis tilter" on an internet search engine

There are many plans for a DIY job if you like as well

http://www.driver.ie/forum/showthread.php?t=75140

for another example...

[cth350]

Skinned Knuckles did a series on rust inhibition and prevention ages ago. Here's the summary...

1. Use lots of elbow grease to get down to bare metal. For a vintage Mercedes, that means removing the undercoating (Gael, your car had it; somebody removed it).

2. Working on an area roughly 1 foot square at a time clean the metal with just about any of the metal prep solutions that have phosphoric acid. This is more elbow grease with a scotch bright pad. Follow the instructions on the bottle with respect to safe application, disposal and cleanup. ((my personal favorite is from the guys that make Kroil)).

3. Paint it with something designed for bare metal. The metal prep will leave behind a white residue. Things like POR-15 and etch primer won't mind that in the slightest. Read the safety instructions about application. Using POR-15 in a sprayer can kill you and others if you don't use the right breathing apparatus.

4. Paint it with something else. The things that are good for bare metal usually aren't happy with exposure to fresh air, sunlight, water and/or ozone.

HTH -CTH