Journal Published Online: 14 February 2019
Volume 8, Issue 1

Effect of Viscosity on the Erosion-Corrosion of Steels Exposed to White Liquor Including Abrasives for Extended Time Periods



Erosion-corrosion is a type of corrosion in which mechanical (erosive) and chemical (corrosive) effects combine to accelerate material loss because of corrosion because of its negative impact on the reformation of a protective oxide layer on a metal surface. Erosion-corrosion has been observed in most industries that utilize alkaline streams such as pulping liquors, including the pulp, paper, nuclear, petrochemical, and pharmaceutical industries. Although erosion-corrosion research has been conducted mainly by studying the effects of changing chemical species and concentrations within the environment and mapping corrosion modes for specific alloys and environments, the mechanical properties of the electrolyte such as its viscosity have been neglected. Erosion-corrosion rate is directly related to flow characteristics such as flow regime, wall shear stress, etc., many of which are directly influenced by viscosity. Furthermore, variable viscosity is a factor in many occurrences of erosion-corrosion, notably black liquor-related corrosion in the pulp and paper industry. To understand such a system, a white liquor electrolyte was spiked with various concentrations of an inert viscosity adjusting additive (agar agar) under alkaline conditions. Corrosion rates were obtained from combinations of white liquor, alumina erodent, and agar agar using mass loss testing over 100 h of C1018 carbon steel, 316L stainless steel, and 2205 duplex stainless steel (DSS) at 60°C. The results showed that higher wall shear stress resulting from a higher viscosity tended to increase the corrosion rate. Erosion-corrosion surfaces were observed using profilometry and scanning electron microscopy, revealing that higher viscosity led to more severe damage but with fewer damage sites. This indicated a lower number of critical impacts because of the higher resistance to flow but higher damage to the passive film because of higher shear stress. In the two-phase structure of 2205 DSS, preferential dissolution of ferrite was observed at a viscosity of 14.86 cP.

Author Information

Baykal, B. Aydin
School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA, USA
Singh, Preet M.
School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA, USA
Pages: 15
Price: $25.00
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Stock #: MPC20180013
ISSN: 2379-1365
DOI: 10.1520/MPC20180013