An experimental study has been performed on a high-capacity steam boiler burning heavy fuel oil to assess cold-end corrosion damages. In this second part of the research, acid corrosion in the rotary continuous-regenerative air heaters (CRAHs) has been analyzed. Corrosion potentiality has been evaluated from both qualitative and quantitative viewpoints. Results have shown that acid corrosion in the CRAHs is reduced when the low-quality heavy fuel oil is mixed with a magnesium-based additive. In this research, two commercial additives have been tested: a magnesium oxide-based slurry and an organometallic one. The best results have been obtained when the organometallic additive was used in the treatment of the heavy fuel. For this experimental condition, an increase in the useful lifetime of the pie-shaped baskets, as well as a decrease in both the acid dew point temperature (ADT) at the stack gases and the pressure drop (fouling) on the CRAHs have been confirmed. (C) 2004 Elsevier B.V. All rights reserved.