Apr 20th, 1:00 PM - 4:00 PM
Investigation of Accelerated Corrosion in a Fresh Water Irrigation System
Dr. Darryl Butt
The Idaho agriculture industry relies on extensive fresh water irrigation systems to help sustain favorable crop cultivation conditions during the growing season. Modern irrigation systems not only transport and distribute fresh water from a source but also regulate pH and fertilizer concentrations to maximize harvest yields. Accelerated corrosion was observed in an irrigation system with recently replaced galvanized steel pipes. The new pipes had experienced more significant corrosion in 3 years than had been observed on older pipes in service for 17 years. A series of electrochemical experiments were conducted to investigate the causes of the accelerated corrosion. These experiments focused on the effect of various concentrations of fertilizer and water mixtures on the corrosion rate of the pipe material. Tests were performed on both the zinc and steel surfaces on the inside of the galvanized steel pipes to simulate corrosion effects before and after the protective zinc layer had been corroded. The pH level of these mixtures was intended to simulate possible environments in the irrigation water. The corroded pipes were examined with scanning electron microscopy (SEM) and optical microscopy for clues of the possible cause of the accelerated corrosion. The images obtained resemble a type of corrosion attack that has been found in other fresh water systems known as microbiologically influenced corrosion (MIC). This evidence, along with the results of the corrosion measurements performed suggests MIC is likely present within the irrigation system.