Brown pipes turning grey

[Macnabpipe]

I have used brown Marley rainwater pipes and gutters in my new house. After a couple of years some of the pipes and gutters have turned grey. It appears to be a coating of some sort and when you scrape it it is still brown underneath. However it turns back to grey after a few minutes. Most of the piping is ok and it is only few pipes that turn to grey.
Does anyone know what causes it and if there is a cure?

 

[KenGMac]

What has possibly happened is that the brown pipes fitted are indeed supposed to be for below ground use? Historically I have seen quite a few of them,

https://www.williamwilson.co.uk/dbdocument/3396/Marley%20Full%20Range.pdf

If not the above?? are the discoloring D/Pipes and Gutters exposed to full sunshine for long periods of time?

The most obvious possibility s are
1/. Sunshine leaching the colour from the plastic?
2/. Air borne contamination [unlikely]

Ken.

 

[Macnabpipe]

What has possibly happened is that the brown pipes fitted are indeed supposed to be for below ground use? Historically I have seen quite a few of them,

https://www.williamwilson.co.uk/dbdocument/3396/Marley%20Full%20Range.pdf

If not the above?? are the discoloring D/Pipes and Gutters exposed to full sunshine for long periods of time?

The most obvious possibility s are
1/. Sunshine leaching the colour from the plastic?
2/. Air borne contamination [unlikely]

Ken.

Hi Ken, thanks for your quick reply. Some of the gutter fittings have also turn grey and they are not for going underground so unlikely to be that for the gutter. The pipe is still a possible reason.
They are exposed to sunlight for long periods but so is the rest of the guttering and pipes attached to them. Having said that there none of the pipes etc on the shaded side of the house turning grey so the sunlight could be playing a part in the problem.

 

[KenGMac]

Have had a look round my local area and a lot of Plastic D/Pipes are indeed [shall I call it ] faded? As far as I can see it is all down to Sunshine ??

As for repair?

Plastic does not tend to like normal oil based paints, My neighbour earlier this Summer painter a couple of D/Pipes.

What he did was to use canned spray paints, similar to spray paint used in model making, but it took several cans the cover rate was small.

The other trick he used was to heavily mask the surrounding stone, he use a one meter square piece of heavy cardboard from an Amazon delivery, knew these packages would somehow become useful??.

Ken.