What is the thing that emerges like a white solid on desert cooler walls after some days of running?

well it's somewhat a silly or i should say a useless question (please don't mind me saying that) as you don't need to know this however if you are so eager to know the answer then i should tell you that that white thing is usually a type of fungus which forms on cooked kidney beans when kept open for some days or of it is on the motor of the fan then it should be something like that which forms on the electrodes of the inverter's batteries over a period of around 5 Months!!!!!!!!!!!!!!!!