[maddog2020]

the coolant tubes that run along the passenger strut tower are made from steel and are cad plated from the factory. The problem is that the CAD plating doesn't go very far inside the tube and due to their age they are starting to rust from the inside out.

Here are some pics from a local 928er.





If you are doing a waterpump/timing belt and see this:



You can be assured that your coolant tube is indeed rusting out.

I've had new versions made from aluminum in left hand drive and right hand drive.



Here are some comparisons.





https://928-innovations.mybigcommerce.com/

[worf]

the coolant tubes that run along the passenger strut tower are made from steel and are cad plated from the factory. The problem is that the CAD plating doesn't go very far inside the tube and due to their age they are starting to rust from the inside out.

Your thesis is correct: some of the coolant hardlines are beginning to rust from the inside out.

But I will argue with your trail of connected dots.

The factory plating is not Cadmium. It is (was) a surface treated electroplated zinc
Good electroplating processes result in all metal surfaces both inside and outside - on a piece as simple as that one - getting plated.
And the factory's supplier's plating processes were very good.
The surface treatment, not ionically driven, isn't as uniform as the plating. But, on the inside, the treatment is less important than on the outside.

Rust on the outside of these is environmental.
Rust on the inside is - mostly - the result of the wrong coolant sitting for years and years.
Rust and pitting on the surface between the hose and the pipe is the same as above exacerbated due to crevice corrosion.

[worf]

If you'd made these out of steel, I'd buy a couple every year or just buy a batch of 10 or 20.

But, aluminum doesn't electroplate and thus I can't achieve the same appearance as the stock line.

[maddog2020]

you can buy plenty of the steel versions from Porsche for over $500 each if you like. you can get these anodized gold to look close to the factory but not exact.

talk to any plater and they will tell you to plate the inside of a tube a wire has to be run inside each tube to get the inside of the tube plated more than an inch at this diameter. The plater that I use does milspec plating for DOD, so I think he may know what he is talking about. I looked at a brand new one a few years ago, fresh out of the porsche bag. I used a bore scope and could see where the plating faded to nothing and bare metal the rest of the way thru the tube.

Sure if you are doing a concours car then by all means buy the factory part. Most owners are struggling to keep the cars on the road at an affordable rate.

[worf]

I qualified what I wrote carefully and stand by what I wrote. In particular the conclusion: the death of these lines is due to old coolant and crevice corrosion. The hole you highlight is exactly where the hose clamp lies. The worst thinning and pitting are the surfaces over which the hoses slip.

My plater is 3rd generation and 50% of throughput is Mil-Spec Cad. I do not dispute that if you do a 30-second rack plate in a static bath with one hook that that line won't get plated on the inside. It won't get uniformly plated on the outside either. Minimum effort almost always results in a poor outcome. That's why I wrote 'good process.'

New non-NOS Porsche steel parts are often - indeed usually now - rusted in the bag. So, I would expect shitty plating - if any - on a new $500 line. If the line you used for your model wasn't NOS it wasn't representative of the originally-supplied parts. And at $500 it was a PCG part not NOS. The NOS parts were $<100.

[maddog2020]

down to the last 3. Roger sold 8 and I've sold almost 30.

[maddog2020]

Original batch sold out and we have a new batch in. And just for Worf we had a couple of yellow ones made