Abstract
Background: Corrosion of materials is a natural phenomenon that is a cause of concern as it has incurred a total damage of billions of dollars to many industries. Many ways of overcoming the corrosion problem such as inhibitors, anodic protections, cathodic protections and coatings are developed. Natural products such as plant extract, amino acids, proteins, and biopolymers have been reported to be efficient corrosion inhibitors. Plant extracts are viewed as rich source of naturally synthesized chemical compounds that can be extracted by simple procedures with low cost. These natural extracts are analogous to the synthetic organic inhibitors and are being proven to work as much as their synthetic counterparts.
Methods: The initial weight of the mild steel specimens was measured using 4 digit model Dewyer SI-234. The initial weight of the coated mild steel specimens was measured. Weight loss experiments were carried out by immersing the coated mild steel specimens in HCl, H2SO4 and HNO3 acids after cleaning and weighing. A medium sized leaf of an Indian Aloe vera is taken and peeled and collected 50ml of the extract. The stem of the banana plant was collected from a local market. The sheets of the stem were separated, crushed in a grinder and the sap is extracted. The sap is stored in the freezer at 18 °C for further use. About 500 gms leaves of the Henna were collected from the garden. It is then cleaned and washed in distilled water. Leaves were blended to batter and the extracts were filtered out.
Results: The surface morphology of the corroded mild steel sample is examined under colonial microscope and pictured by a mobile camera. The pictures reveal that the corrosion occurred, and the acids affected the inhibitor layer. Calculated data from the experiment are plotted using the Igor software. Weight loss of the mild steel without any inhibitor by acids is plotted against time. This plot reveals that HCL corrodes more than HNO3 than H2SO4, proving that HCL is more corrosive on Mild Steel Sample. HNO3 corrodes the sample from the 48th hour corroding about ~7 grams. The weight loss of the sample with Aloe Vera extract on various acids. From the plot aloe vera shows more resistance towards HNO3 than HCL and less protection towards H2SO4. The weight loss of the sample with banana sap extract on various acids. It shows the best protection against HNO3.
Conclusions: Inhibition efficiency of the aloe vera, Banana sap and the henna extract are found to be higher than the other green inhibitors ranging from 70% to 98% against HNO3, H2SO4 and HCL. Henna extract is found to be more efficient than the rest. Relative corrosion resistance calculated from the corrosion rate is found to be outstanding. Relative corrosion resistance calculated from the corrosion rate is found to be outstanding. The green inhibitor reported in this work is found to be an excellent replacement of the chemical coating present today. These green inhibitors are ecofriendly, nontoxic, leading to zero pollution thus certainly needed for this generation.
Keywords: Waterbath method, spin coating extracts, green inhibitors, corrosion rate, inhibition efficiency, aloe vera, banana sap and henna.
Graphical Abstract
11
2