painted metal coolant pipe

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Car is 2000 Mazda MPV which uses Ford's Duratec 2.5L V6. The smallest V6 there is. Anyway, in preparation for some repair at next coolant exchange, I ordered the engine oil cooler and the pipes that connect to the cooler. Original engine oil cooler is right above the oil filter, and the coolant spouts are rusted.

The original coolant pipes that go to/from the cooler include a section of "plastic" tubes (because they snake between the engine block and the exhaust manifold), which naturally does not have rust issue. But the new pipes I bought (OE part) have painted metal sections. Questions I have:

Doesn't coolant eat painted? paint inside the pipe will get resolved, leaving bare iron, which is going to rust from inside out. What would car makers choose to use painted metal pipe for coolant? I googled the net, and found other car makes do the same thing, but why? I don't want to re-use the old part because it's been there for 12+ years. Bu the new metal pipe really makes me worry, and there's simply no batter alternative. sigh.
 
Here's a picture of the coolant pipes.

P1010570_coolant_lines.jpg
 
Don't worry about this...

Bare iron doesn't rust in coolant unless the coolant is worn out and old...if coolant rusted iron/steel...what do you think would happen to iron engine blocks?
 
If I had a choice between a metal pipe and a plastic pipe as part of the cooling system, I'd choose the metal part every time. As Chris notes, the coolant is protecting the inside of the pipe - it has additive to prevent that type of corrosion. The metal also won't get brittle like a lot of plastics do after repeated heat cycling.

There may be a reason the repalcement parts are metal.
 
The coolant will not eat the paint that is used on those pipes. They thought of that when they chose the paint. A lot of those automotive engineers are smart guys, you know, even if some occasionally do something obviously nutzoid. The paint provides protection to the pipes where they're exposed to open air and a little extra protection against electrolytic corrosion on the inside.
 
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