Try a variation of the classic bleach battery which has an anode of aluminum in aqueous NaOCl/NaCl. The latter is commonly sold as disinfecting chlorine bleach prepared from the action of chlorine on aqueous NaOH.
However, in place of the usual noble cathode of copper, I would try instead a freshly prepared inexpensive high surface area carbon cathode. For example, I have experienced good results from burnt food, to quote a source:
In cooking utensils, burnt food may produce carbon deposits with resulting rapid galvanic corrosion from the aluminum-carbon couple [474, 475].
Consider burnt bread with which I have had some success. Studies on advanced oxidation processes (AOP) interestingly cite, per my recollection, also the use of burnt coconut shells (likely reflecting local access).
Also, applying heat should promote the rate of the anodic corrosion of the aluminum (alloy?), which normally involves an inception period (which is characteristic of an electrochemical reaction).
Rationalization: Your Al contamination on the steel file may consist of an aluminum alloy, making it less anodic (so that, its tendency to corrode is reduced). Also, the relative surface area of the Al-steel anode to the cathode may not be small, which also reduces its rate of corrosion. Hence, the recommended use of a high surface area carbon cathode. Now, one could purchase activated carbon but I would try my home recipe if your problem is expected to be ongoing and you are looking for an efficient low-cost solution.
Note: In the current situation, the iron/steel file is the cathode which is coated with aluminum. As such, the cathode has little surface area relative to the anodic Al, which is the reverse of what one should have for fast electrochemical dissolution.