Atmospheric corrosivity in a bagasse/coal co-firing power plant influenced by a tropical marine climate

Introduction

Combined marine and industrial conditions form a complex climate that complicates corrosion prediction in energy infrastructure design. The impact of pollutant mix, driven by wind action and high humidity, may affect the evolution of corrosion product formation. This study provides valuable insights into the corrosivity of a unique marine-industrial location on the tropical island of Mauritius.

Methods

S235-grade carbon steel plates are subjected to a 14-month atmospheric exposure test at a bagasse/coal thermal power plant situated 3 km from the tropical coastal sea. Weight loss analysis is performed with triplicate specimens retrieved at specific time points to determine the corrosion kinetics. Furthermore, surface analysis using SEM-EDS and FTIR helps to identify the rust phases.

Results

The results demonstrate a corrosion rate (340 gm^-2a^-1) in the medium ISO 9223 category (C3). The chloride (Cl^-) deposition rate is elevated at 74 mg m^-2 d^-1 but does not cause the formation of flaky corrosion layers. Lepidocrocite (γ-FeOOH) and goethite (α-FeOOH) are the predominant rust phases. Also, sulphur dioxide (SO₂) emissions do not lead to significant surface deposition, mainly due to the low sulphur content of bagasse and the location of the gas stack relative to the exposure rack.

Conclusion

Formation of stable corrosion products, such as (α-FeOOH), limits Cl^- penetration due to the inherently compact and dense rust layer. Extreme corrosion protection measures may not be required in bagasse/coal cogeneration plants. However, higher times of wetness and lower SO₂ emissions may lead to conditions more conducive to chloride attack in a marine region.