The inhibition of Carica papayaleaves extract on the corrosion of cold worked and annealed mild steel in HCl and NaOH solutionsusing a weight loss technique

• Main Authors: Samuel Uzoma Nwigwe, Reginald Umunakwe, Stephen Ogbonna Mbam, Moses Yibowei, Kooffreh Okon, Godwin Kalu-Uka
• Format: Article
• Language: English
• Published: Khon Kaen University 2019-06-01
• Series: Engineering and Applied Science Research
• Subjects: Mild stee; Carica papaya; Leafextract; Corrosion; Inhibition
• Online Access: https://www.tci-thaijo.org/index.php/easr/article/view/151118/135502

The current work investigates the corrosion inhibition of cold worked and annealed mild steel in 0.5 M HCl and0.5 M NaOH solutionswithCarica papaya leafextract as an inhibitor. The as-received diameter of the mild steel rods was 4.42 mm before some of them were cold drawn to 3.35 mm wire bars. Rods that were 30 mminlength were cutfrom the as-received, cold worked and annealed samples. The cut samples were thoroughly pickled, dried and weighedbefore they were suspended in an aggressive media that contained theinhibitor as well as in the media without inhibitor. The samples were examinedon the 3rd, 5th, 7th, 10th, 12th, 14thand 17thdays, and then, pickled, dried and reweighed.In the 0.5 M HClsolution without inhibitor, maximum corrosion rates of the as-received and cold worked samples were reportedon the 5thday, andtheir values were 1.0x10-4 and 1.3x10-4 g/cm2h,respectively.Themaximum corrosion rate of the annealed sample was reportedon the 12thday and its value was 5.9x10-5g/cm2h. The extract was able to reduce the maximum corrosion rates of the as-received, cold worked and annealed samples in 0.5 M HCl solution by 54.1 %, 42 %, and23.1 %,respectively. Similarly, in a0.5 M NaOH solution without inhibitor, maximum corrosion rates of the as-received and cold worked samples were reportedon the 5thday.Their values were 7.0x10-5 and 8.8x10-5 g/cm2h,respectively.Themaximum corrosion rate of the annealed sample was reportedon the 12thday and its value was 4.1x10-5g/cm2h. The inhibitor reducedthe maximum corrosion rates in a 0.5MNaOH solution by 53.8 %, 51.4 % and 33.3 % for the as-received, cold worked and annealed samples respectively. The corrosion rates of all the samples were reduced in the media that contained the inhibitor.