Metallurgical Evaluation of Corroded Piping - Pit Seen at Center
Metallurgical Evaluation of Corroded Piping - Pit Seen at Center

Failure analysis on corroded irrigation piping – possibly related to issues with self-draining gaskets and/or non-conformance to specification.

Metallurgical Investigation involved:

  • Chemical analysis to identify the alloy
  • Stereo microscopy of corroded ID surfaces
  • Cross section examination to determine alloy microstructure and mode of corrosion
  • Scanning electron microscopy

Chemical Analysis discovered the primary composition was copper (Cu), Iron (Fe), Magnesium (Mg), Manganese (Mn), Silicon (Si), and Zinc (Zn). The presence of 0.84 weight percent manganese indicates that the alloy is a 3000 series aluminum alloy. These aluminum alloys can be work hardened, but not heat treated. The composition of the alloy most closely matches type 3004, although the alloy is somewhat below specification in manganese and somewhat above the specification in iron.

Subsequent stereo microscopy discovered corrosion pits, and scanning electron microscopy (SEM) discovered chloride pitting – a common occurrence as the chloride ion is known to facilitate breakdown of the aluminum oxide film.

In order to eliminate this mechanism promoting accelerated corrosion attack, one of our recommendations was to reduce the chlorine/chloride in the irrigation fluid system.

 

 


We Perform Engineering Failure Analysis Services on Equipment for Clients in Industries including Agriculture, Civil and Construction.

(412) 835-5007

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