Longer 'lasting' color...

[Externet]

Hello all.

Noticed red vehicles and items fading their color coatings and rust surfacing earlier than in other colored coatings.

Which metal roofing color should last longer from showing corrosion -for equal paints composition- ?

-Image borrowed from web-

[swansont]

2 hours ago, Externet said:

Noticed red vehicles and items fading their color coatings and rust surfacing earlier than in other colored coatings.

Red items are red because they reflect red and absorb the shorter-wavelength light (blue) which is higher in energy, and tends to break bonds. Once bonds are broken, the molecule doesn’t have the same reflection and absorption spectrum. So they fade.

[StringJunky]

That particular picture could be efflorescence and not fading; leaching of consitituents to the surface.. Those are masonry pantiles on that roof.

[StringJunky]

Rust-o-leum company, is  US+-based iirc, makes stuff for that application. This is a UK reseller company that stocks them, and you can see from here the sort of solutions that may be available to you in the US. 

https://www.promain.co.uk/roof-paints-primers-cleaners/metal-roofs-cladding-paint.html

 

[John Cuthber]

3 hours ago, swansont said:

Red items are red because they reflect red and absorb the shorter-wavelength light (blue) which is higher in energy, and tends to break bonds. Once bonds are broken, the molecule doesn’t have the same reflection and absorption spectrum. So they fade.

Yes and no.
The molecule absorbs energy and some electrons get shuffled round. 
But ordinarily, those electrons manage to transfer their energy to vibrations of the molecule and it's dissipated as heat.
So the molecule isn't usually permanently damaged.
We deliberately chose molecules for their ability to stand up to this process even when it's repeated many times.

Most fading by sunlight is actually caused by UV rather than visible light.

UV photons carry enough energy to break bonds and that's not so easy to recover from.
On the other hand, as has been pointed out, those are clay tiles. The pigment is essentially iron oxide and even if that molecule gets damage, the only plausible products are iron and oxygen. 
If any iron is produced, it wont be long before it rusts back to the original orange/ brown colour.

So it's pretty much permanently light fast.

The discolouration is probably, as SJ says, efflorescence. (I can't absolutely rule out leaching by acid rain or something if the place is in a chemical works or something.)

 

[Externet]

2 hours ago, StringJunky said:

That particular picture could be efflorescence and not fading; leaching of consitituents to the surface.. Those are masonry pantiles on that roof.

Thanks. That particular picture is a metal roof, imitation of tiles or disguised :

Am not after painting; but will buy new roof building a house and wanted to decide for a more lasting color... not for the looks but for durability.

[John Cuthber]

OK, pretend I was talking about the bricks.

 

[Externet]

My roof is in post #5 at --> https://forum.allaboutcircuits.com/threads/where-a-fuse-will-not-protect.182027/  

And somewhere else in this forum too.-->post #4 at   https://www.scienceforums.net/topic/127669-positioning-of-solar-panels/#comment-1215829

How is your roof ?

Edited again... Some text dissapeared while editing, cannot find the original now

Edited March 20, 2023 by Externet
added link

[studiot]

I don't know what they paint bridge steelwork with in America, but the UK standard uses a 7 coat MIO recipe.

MIO = micaceous iron oxide.

The obviously thick paint contains tiny flakes of mica which diffuse the incoming lightfrom penetrating as far as the base steel.

Sadly the coulour pigments used are almost exclusively battleship grey or puke green.

British Rail has experimented with some brighter colours.

 

I have experimented with some modern alternatives and every time I drive up the motorway I look to see how they are going.

I can see no visible degradation 25 years on.

[StringJunky]

1 hour ago, Externet said:

Thanks. That particular picture is a metal roof, imitation of tiles or disguised :

Am not after painting; but will buy new roof building a house and wanted to decide for a more lasting color... not for the looks but for durability.

The new roof is going to be plain metal for you to paint, or already finished?

[Externet]

Hi.  It is supplied already painted, I have to choose the color.

 

[StringJunky]

probably the lightest colour

[John Cuthber]

Carbon black is cheap and almost indestructible. It will also protect the underlying material from light/ UV.
Aluminium paint does the best job of thermal isolation.