PAN PITTING CORROSION

摘要

During the 2013-2014 maintenance season, routine pressure vessel inspections at Invicta and Kalamia mills found pitting corrosion in three recently installed batch vacuum pans. The pits measured 2-3 mm deep and 3-4 mm in diameter, with Invicta pan No. 7 experiencing the most severe pitting. As these pans had only been in service one to two seasons, a metallurgist was engaged to determine the root cause of the pitting corrosion and offer solutions as this type of corrosion can be aggressive. This paper details the findings of the metallurgical investigation and the redesign undertaken to prevent potential pitting corrosion. Also discussed are the analysis and trials undertaken for louvre spray which associates the pitting corrosion to the mode of operation of the pan.