Corrosion failure of titanium tubes of a heat exchanger for the heating of dissolving lye. (November 2021)

• Record Type: Journal Article
• Authors: Romanovski, Valentin; Hedberg, Yolanda S.; Paspelau, Andrei; Frantskevich, Vitali; Noël, James J.; Romanovskaia, Elena
• Is Part Of: Engineering failure analysis. Volume 129(2021)
• Publication Date: 2021-11
• Subjects: Titanium -- Corrosion -- Heat-exchanger -- Chlorine -- Sylvinite ore -- Cracking; System failures (Engineering) -- Periodicals; Fracture mechanics -- Periodicals; Reliability (Engineering) -- Periodicals; Pannes -- Périodiques; Rupture, Mécanique de la -- Périodiques; Fiabilité -- Périodiques; Fracture mechanics; Reliability (Engineering); System failures (Engineering); Periodicals; Electronic journals; 620.112
• DOI: 10.1016/j.engfailanal.2021.105722
• Languages: English
• ISSNs: 1350-6307

Abstract

Highlights: Corrosion of titanium tubes of a heat exchanger to heat lye investigated. Exhibited a failure case induced by local overheating, rapid cracking and erosion. Possibly hydrogen embrittlement due to Fe, Cu, and Zn deposits. Pitting corrosion started above 80 °C in the simulated dissolving lye environment. Rapid cracking through both oxide and metal matrix without Cl enrichment. Abstract: Corrosion of titanium heat exchangers in the processing of sylvinite ore is undesirable from economic, safety, and process sustainability perspectives. Triggered by an industrial case, we investigated the extent of corrosion during simulated contact with sylvinite ore (in dissolving lye) in relevant conditions. Detailed characterization of the failed tubes and corrosion products was carried out to understand the mechanism of failure. Corrosion of titanium (Grade 2) tubes was investigated at room temperature, 60, 70, 80, and 90 °C. After electrochemical and surface morphology analysis, we found that pitting corrosion of the titanium tube material sharply increased above 80 °C in the simulated sylvinite ore environment (pH 7.1). The failure analysis revealed extensive degradation by transgranular cracking through both the oxide and metal matrix, likely caused by a combination of the high temperature, pressure, possible vibrations, the build-up of lye deposits causing crevices, the high salt content of the lye, and possibly metal (copper, iron, zinc) impurities/deposits in or on the titanium metal, which can catalyze hydrogen evolution.