Aluminium body paintwork advice

[XKJon]

I have some minor surface under paint corrosion (Black car) on two places on my 2011 XK. I have extensive experience re steel bodies but can anyone offer some extra guidance when sorting this problem on an alloy bodied car. I presume its necessary to clean off and gently rub down the small area that is affected, under normal circumstances I would then treat this with chemical degreasing agent, paint with etching primer then paint / lacquer.  The area is about 15mm square on a bodywork corner directly behind the front wheels on both sides. I have removed the liner and the back is 100 percent solid so its definitely caused by stone rash and then alloy corrosion. Any guidance appreciated.