Pressure losses measured on a compressed air net as a consequence of corrosion

On a compressed air net DN150 and DN100, long of around 300 meters, we measured pressure losses 250 to 500 times higher than expected on the basis of standard pressure loss calculation.
We believe that rust is responsible for this exceptional pressure loss!
Compressed air was supposed to be dried either by a frigorific dryer – insufficient in winter – or by an adsorption “MD” dryer – a good dryer which was excessively oversized.