Once the source is stopped dutchboy recommends.
How to remove aluminum siding stains from brick.
Mix one part bleach with one part water.
How to remove deck stain from aluminum siding hunker.
However don t use muriatic acid which is commonly suggested because it can stain or bleach many colors of brick and cause aluminum window frames to corrode.
Clean the surface of the aluminum siding with a water sprayer.
The white chalky film that sits on your brick right next to the aluminum siding is oxidation.
Brick areas that are stained by chalk run down should be scrubbed with a stiff brush and detergent.
Here is a quick how to video for removing oxidation from brick on an old house.
Mix 1 3 of a cup of laundry soap and 6 gallons of water.
Hope it helps someone else because there really isn t much out there on this.
Dec 29 2015 combining brick and siding on a home s exterior looks nice but can cause a few extra maintenance chores for the homeowner.
Mix strong detergent such as trisodium phosphate tsp with warm water in a plastic.
Instead several brick cleaners are available that because of special buffers work well without the staining problem.
Put on a pair of latex or rubber gloves.
Apply to the stains and scrub with a soft bristled brush.
Scrub the stained area thoroughly.
Removing stains from brick caused by siding using acid and power washing is a great way to get your house or building looking new again.
Professional cleaning may be required to remove this staining.
Saturate a rag with mineral spirits.
Scrub at the stain turning and rewetting the rag frequently.
Your local brick dealer probably carries these products.
Rinse the stained area with a hose to remove large pieces of dirt and debris.
I d say the first thing to do would be to eliminate the source of the problem either repaint replace or seal the siding.