
This is my feature wall, its 90x45mm verticals. i would like to attach my TV on this but without any damage to it

My idea is 2x Vertical posts which are held against the feature wall with horizontal wood on the back and the TV bracket at the front. My question is what sized timber do i need as Bunnings doesn't sell 4x2 (90x42) on thier web site and i need 1800mm high?
The total weight is 40kg. So what thickness of wood do i need?