White from old alluminum Siding stained Brick

Hello everyone,

I have a brick house with the old white alluminum siding that is chalking. This chalking has dripped down the side of the house a little and made some of the brick white.

Please tell me how I may be able to remove this without ruining the brick. I have tried a high pressure washer and it didn't work so well. Is there a chemical or something I can use?

Thanks

Stephen