Abstract
Corrosion behaviour of cast iron and low alloy steel in cocoa liquor and well water was investigated. The average weight losses of the specimens were measured using digital weighing balance. The results showed that the weight losses of both cast iron and low alloy steel in both media increases with time. Corrosion rate of cast iron in cocoa liquor increases rapidly with time for up to 336 hours (1000 μm/yr), but in well water the rapid rate of corrosion only lasted up to 187 hours (1160 μm/yr) thereafter it continuously dropping until 264 hours (667 μm/yr) after which it remains constant. Low alloy steel corroded faster in cocoa liquor up to 264 hours (200 μm/yr), whereas the initial rapid corrosion rate only lasted up to 168 hours (180 μm/yr) in well water environment. The results revealed that low alloy steel exhibited better corrosion resistance in both media, with cocoa liquor been more aggressive. Thus, low alloy steel will be a better material for piping and pumping system in cocoa processing industries.
Highlights
Grey cast iron is a high carbon ferrous material that was previously been used for water and wastewater services pipes in several parts of the globe [1,2]
Crude protein is responsible for gradual degradation of both grey cast irons and low alloy steel while fat inhibits their degradation when exposed to cocoa liquor
The relationship between weight loss/area (g/cm2) and exposure time of both the cast iron and low alloy steel samples in cocoa liquor and well water are shown in Figures 1 and 2
Summary
Grey cast iron is a high carbon ferrous material that was previously been used for water and wastewater services pipes in several parts of the globe [1,2]. Most of the carbon in this material is in the form of continuous network of flake graphite platelets, which are dispersed throughout the metal matrix This matrix is the major factor controlling its mechanical properties and is responsible for its relative weakness and lack of ductility [3]. A combination of factors which may include corrosion damage, external loading, internal pressure and manufacturing flaws contribute significantly to the failure of these pipes [4,5]. This failure becomes accelerated as the pipes age resulting into leakages [6]. In order to prevent this type of failure, efforts were geared towards finding alternative high corrosion resistance alloys in both water and other similar environments [7]
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