Sulphur-induced corrosion in Duplex stainless
steel: a case study in a petroleum refinery
G. Siracusa & A. D. La Rosa
Dipartimento di Metodologie Fisiche e Chimiche per l’Ingegneria
(DMFCI), Facoltà di Ingegneria, Università di Catania, Italy
Abstract
From the introduction of its first-generation, Duplex (austeno-ferritic) steel has
seen a steady increase in popularity [1]. Recently, the production of highstrength, corrosion resistant super-duplex coil has been implemented in several
applications.
The case study we present in this paper concerns its use in a set of tubes of a
heat exchanger affected by corrosion. The tubes material, S31803 Duplex
stainless steel, is particularly suited to applications where corrosion is likely due
to chlorides and/or sulphides being present. The heat exchanger operates in a
chloride environment due to marine water on the inner side while the outer side
is in contact with a hydrocarbon mixture rich in sulphur. It also has high
resistance to general, pitting, crevice and erosion corrosion and to corrosion
fatigue.
The aim of our study is to understand the corrosion mechanism occurring and
the factors responsible (e.g. the presence of chlorides, sulphides etc.) using
several techniques for the experimental characterisation of the materials
including optical microscopy and SEM (scanning electron micrography).
Keywords: Duplex steel, pitting corrosion, sulphide cracking, SEM.
1
Introduction
The first-generation Duplex stainless steels were developed more than 70 years
ago in Sweden for use in the sulfite paper industry. Duplex alloys were originally
created to combat corrosion problems caused by chloride-bearing cooling waters
and other aggressive chemical process fluids such as sulphides depending on the
concentrations. Called Duplex because of its mixed microstructure with about
High Performance Structures and Materials II, C.A. Brebbia & W.P. De Wilde (Editors)
© 2004 WIT Press, www.witpress.com, ISBN 1-85312-717-5