Biocorrosion of stainless steel grade 304L (SS304L) in sugar cane juice

Abstract

The main objective of this research study is to assess the behaviour of stainless steel AISI 304L in contact with sugar cane juice. Stainless steel grade 304L is largely used in the sugar cane industry but the acidic nature of sugar cane juice pose a serious challenge in maintaining the life span of vital components. Sugar cane juice is acid having a pH value of around 5.6 at extraction. This acidic property is accounted for by the presence of a variety of acids namely: aconitic, citric, malic, oxalic, glycolic, mesaonic, tartic, succinic, fumaric and syringic in sugar cane juice. In addition to these acids there are approximately 50 different kinds of microorganisms present in the green cane and which are very active. These microorganisms will act as a contributor to a rather quick drop in pH (pH∼3.1) of the sugar cane juice once extracted. The more so, several minerals like water, salt, sulphate and silica are also present throughout the process line and are other contributor in the surface degradation wear mechanism. Faced with all these adverse elements, it is therefore fundamental to investigate thoroughly in the wear corrosion mechanism and biocorrosion on stainless steel grade 304L. To evaluate the mass loss, several corrosion experimentations were carried with the help of a potentiostat both in a sterilized juice and none sterilized juice. From these experimentations, it has been noted that corrosion was present on the surface of the disc (SS304L) in contact with none sterilized juice in the form of pitting while no corrosion wear was observed in the case of sterilized juice. The presence of biofilm was also observed on the sample disc surface. Biofilm formed on the surface of the sample disc was transferred to a potato dextrose agar (PDA) plate by stamping the disc in a circular sequence on the plate in sterilized condition in view to measure the density and resistance of the film. It was noted through this stamping protocol that the biofilm was very resistant due to the fact that after 12 stamping time we still observe the trace of the biofilm on the PDA plate. Microorganisms present in the biofilm have growth on the PDA plate and isolation of each colony was carried out in view of their identification.