To me it’s case by case.
What coil am I cleaning!
What kind of water source and pressure do I have to work with..
Which coil is it! How thick (deep) is the Coil! How clogged is the Coil, What’s on the Coil? Is it in a garage, out back, on a roof, in a closet, suspended in a ceiling??? Will I have to pull the Coil to clean? If I can share one thing with you after cleaning with any chemical….Rinse, Rinse, Rinse and then Rinse again!!
I try to stay away from chemicals unless it is needed. Usually rooftops which reside next to or near a kitchen exhaust get coated with grease and become a real mess. In these situations i use the chemicals but i still usually dilute more than is recomended...
never ever have problems with coil cleanings usually salt deterioration causes that
Salt is a problem here in Florida thats for sure but, this was not a salt problem. The front of the Coil that was exposed and easily rinsed is just fine. The whole mall had the same units and none were this bad. This particular customer had the Coils cleaned once a year under the Maintenance agreement. This is the result of a lazy persons work or, lack of knowledge on how to use a product.
For my part you follow the mfg directions as to chem strength and rinse long and strong. You are not going to degrade the coil beyond usable condition before it's life span is reached. The problem I most often see is a dirty condenser coil, and many more compressors are lost due to this than coils failing. this goes for hvac as well as refrig or ice machines. In a commercial setting such as a restaurant the contaminants produced by hood exhaust far out weigh the degradation caused by condenser coil cleaning chemicals. Also in an environment like Metro Atlanta the smog factor just adds to the oxidation of aluminum fins and in cleaning AC coils and documenting pressures before and after the benefits of chemical cleaners were immediately evident.