How to remove marks and staining from outdoor render

bnason

 I have significant marks yellow, white and dark on one of my front rendered pillars. I have tried to power wash these off however there has been little to no effect. I have noticed that some of this is raised. What products do I need to remove this as I don't just want to paint over it.

MitchellMc

Welcome to the Bunnings Workshop community @bnason. It's great to have you join us and many thanks for your question.

I believe you have limited options if you don't want to paint over this area. It appears you have both rust and salts permeating from the material. The white colouring is commonly called efflorescence and is often seen on new builds.

This is not something that can be washed off but rather is coming out of the cement. 

You could certainly try using Crommelin 4L Efflorescence Remover as it might disguise what had already reached the surface. CLR Calcium Lime Rust Remover might also have some effect on the rusty areas.

Let me mention a few helpful members @JDE, @Stuardo, @Noyade, @Brad to see if they have any additional ideas.

Mitchell