Factors Affecting the Corrosive Behavior of Used Cooking Oils and a Non-Edible Fish Oil That Are in Contact with Ferrous Metals

Abstract

The corrosion behavior of three used cooking oils and one non-edible fish oil was experimentally investigated by the immersion test of iron rods at room temperature. The corrosivity of the tested oils was indirectly determined from the amount of the dissolved iron in the tested oils after the immersion test. Different factors that affect the corrosive behavior of the tested oils were assessed. Among the tested oils, the fish oil showed the highest amount of dissolved iron owing to its chemical properties such as high water content and acid number. In general, water content and acid number have direct effects on the amount of dissolved iron. The addition of oleic acid to the used cooking oil resulted in a 60% less amount of dissolved iron. It was suggested that the addition of oleic acid prompted the formation of a monolayer, which inhibited the permeation of oxygen and water to the surface of the iron rod. Moreover, the addition of glycerol gave the lowest amount of dissolved iron in the oil sample owing to its ability to bind water molecules and form microemulsions in the presence of a surfactant (for example, oleic acid).

Metal Rod Surfaces after Exposure to Used Cooking Oils

“…TBA (98%), used as a corrosion inhibitor, was purchased from Sigma-Aldrich (Saint Louis, MO, USA). The other chemicals used for chemical analyses are described in [13,26,27]. All chemicals and solvents used in the experiment were of analytical reagent grade.…”

“…Hydrogen was used as a carrier gas with a flow rate of 0.8 mL/min. Details on the oven temperatures and gas flow rates can be found in [13]. The individual components were identified by capillary gas chromatography-mass spectrometry (GC-MS) analysis with a Hewlett-Packard (HP) 6890-5973 GC-quadrupole-MSD instrument (Palo Alto, CA, USA), using helium as carrier gas.…”

“…Hydrogen was the carrier gas with a flow rate of 7 mL/min. Details of the temperatures in a wide-bore GC oven and gas flow rates can be found in our previous study [13].…”

“…According to Bruun et al [13], oleic acid or oleic acid and glycerol additions prevented corrosion of steel rods exposed to UCOs. Fazal et al [14] reported a significant increase in corrosion rate upon immersion of metals in fossil and biodiesel samples at 27 • C, 50 • C, and 80 • C for 50 days.…”

“…In our previous works, the chemical, physical, and thermal properties and the effect of storage time on the corrosivity of bio-oils were investigated [13,26,27]. The corrosiveness of different bio-oils during storage and usage are some of the concerns yet to be investigated for addressing compatibility issues.…”