To reach the flange you need to remove the aluminum siding trim around the window but that may prove difficult.
How to take off aluminum siding.
Put on your protective gloves safety glasses and face mask before you start spraying.
Combine cream of tartar with baking soda.
Inspect the siding for loose sections.
Locate the area of your aluminum siding that is damaged.
Slowly add hydrogen peroxide until a thick paste forms.
You will use the utility knife to cut or score two vertical lines on either side of the damaged part of the siding.
If none are loose then start at the top section.
Directly scrub the aluminum siding with a soft scrubber dipped in the mixture.
Combine a few slices of fresh lemon vinegar and warm water in a five gallon bucket.
Pull the bottom down and away and then you should be able to simply unzip that piece horizontally across the wall all the way down to the end.
If you cannot cut through the aluminum with a utility knife and strength you can use a screwdriver and hammer to get the line started.
A loose siding section may be the easiest to remove.
Spray tsp onto wet aluminum siding.
Wash away paste with hot water.
Pull out the bottom locking edge of the siding from the section below it with a siding removal tool.
Using a metal clothes hanger or other small hooks dig into the end of one of the pieces of siding which will allow you to pull it off.
If you re using a traditional chemical sprayer pump the tank until you feel resistance.
Place scraps of wood underneath the edge of the upper piece to expose the nail flange of the piece that you are removing.
How much you use depends on the size of your home.
Rinsing with the solution may also help remove soap scum if you started with the laundry detergent method.
With the ryobi chemical sprayer you just pop in a battery and turn it on.
The wood will hold the upper piece of siding out of the way.