My son and I just finished cleaning the air conditioning unit this afternoon. The condenser is corroded due to neglect. Anyone here has suggestions on how to stop or at least minimize the spread of corrosion aside from regular cleaning?

By the way, usual charge for cleaning is 400 Pesos. I said to my youngest son that we saved 400 since we did the cleaning. So I followed it up by saying that I will take 200 from it and the other half​, he share it to his older brother. He is more than happy to comply.