Failure of Hastelloy C-276 pump impeller in hydrochloric acid

This paper presents the results of a failure investigation carried out on a cast Hastelloy C-276 pump impeller that suffered general corrosion in 32% hydrochloric acid at ambient temperature in a chemical plant. Microscopic examination revealed that the attack was crystallographic in nature. The attack was more enhanced at the interdendritic arm spacing as well as the boundaries of columnar grains, resulting in deep grooves. Taking into consideration that the local temperature could reach up to 50 °C in the summer months, Hastelloy C-276 was judged to be unsuitable material for applications involving 32% HCl. A search into a suitable alternative alloy did not provide a satisfactory answer. Therefore, rubber-lined pump impeller was considered the better alternative.