Identification and Characterization of Corrosion Scale of Cooler Heat Exchanger

The formation of hard scale due to cooling water corrosion has significant effect
in reducing the heat transfer performance and integrity of heat exchanger. The
objectives of this study are to identify the corrosion products of the internal heat
exchanger tube, to characterize the mechanical and chemical properties of rust products
in order to propose better cleaning method. The sample was obtained from PETRONAS
refinery plant which then been cut and analysed. The identification of the corrosion
products by X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy
(FESEM)/Energy Dispersive X-ray Spectroscopy (EDX). Mechanical properties for the
corrosion products are characterized using Vickers microhardness test and the
dissolution of rust scale or the cleaning methods for the characterization of the chemical
properties. The results found from XRD are Iron oxide Fe2O3, Hematite a-Fe2O3,
Lepidocrocite g-Fe2O3 / Fe2O3.H2O / Fe + 3O(OH), Goethite a-FeOOH / Fe2O3.H2O
and Magnetite Fe3O4. Moreover, Goethite α-FeOOH (cotton ball), Lepidocrocite g-
FeOOH (fine crystal plate), cracking and flaking are found with FESEM and EDX
approved the existence of their elements. From the hardness test, the hardness value
found is 110HV. The corrosion scale was successfully removed by using industrial
FOVAC F315 Rust Remover. In conclusion, laboratory characterization of corrosion
scale can assist plant operator to provide better heat exchanger cleaning procedure.