Hughes 500. Agree totally , I have operated C20Bs for over 25 years less than 40 miles from the coast( and often at the coast ) never comp. washed except at the annual (even before the days of coated wheels) and never had a problem. Not a fan of leaving all that water in there.
However at annual/100hr we inspect the compressor wheels very carefully, for corrosion not just the case halves but never found any. Last case halves served 9 years ! Always kept in heated hangar at min 15c