I believe this is the white pigment from the powder coating on the metal siding that is washing down onto your brick. Yes, you can remove the streaks yourself but this will continue to be a persistent problem until the siding above is removed or re-coated.
The powder coat finish of the metal siding is deteriorating and oxidizing. This has no effect on the siding’s performance, only its appearance.
Removal of the Oxidation Directions
Please note: this may be very labor intensive and dangerous depending on the chemicals you use. Please take appropriate safety precautions or consider hiring a professional if you are uncomfortable with doing the following tasks. Also, your clothing will be ruined at the end of this project.
1: Rinse the stained area with a hose to remove large pieces of dirt and debris.
2: Mix one part bleach with one part water. Dip a sponge into the solution and apply it to the stain. Let the bleach and water sit on the stain for 15 minutes.
3: Scrub the stained area thoroughly. Choose a synthetic bristled brush. Steel or metal brushes will damage the brick. You can remove most of the oxidation with heavy pressure and scrubbing. Rinse and dilute area thoroughly to protect foliage around the home. If the oxidation is not completely removed, continue to Step 4.
4: This is a test cleaning of a small area to be sure the following chemicals do not damage the surface of the brick. Put on rubber gloves. Mix 1 lb. oxalic acid with 1 gallon of water. Put a small amount of the solution on a brick to test the effects. Let the solution sit for 15 minutes. Remove with clean water. Rinse and dilute area thoroughly to protect foliage around the home because oxalic acid is toxic to foliage. If the brick is not stained or damaged, proceed to Step 5.
5: Apply the oxalic acid solution to all of the oxidation areas. Let the solution sit on the brick for 5 minutes. Rinse with a garden hose to remove all chemicals and dilute area thoroughly to protect foliage around the home.
Without seeing your home, it is impossible to estimate how long or how much it will cost to remove the white streaks from your brick. But considering how labor-intensive and potentially dangerous the chemicals involved are, it’s usually a wiser move to hire professionals to handle this for you. If you would like expert help with evaluating this project or recommending a professional to do the work, please call our office at 314.909.1800 or contact us here.