On Monday, 20 July 2020 10:49:42 UTC+1, Andrew wrote:
There is an aluminium extrusion that I want to use for an LED strip
light. But, it is anodized and I want it painted the same colour as the
wall. It will be inside and 8ft above ground so well out of the way of
any knocks or wear.

What preparation would I have to do to allow it to take Vinyl Matt paint?

Depends how it is sealed most cheap stuff will have a lacquer type finish more exotic is teflon, neither of which are good bases for paint. A rub down with fine wet & dry will remove the top surface but take care the oxide layer is only microns thick and it is easy to rub down to the base metal. Then again if you are painting that may not matter too much.

Richard