Use of fatty amides and anionic surfactants as corrosion inhibitors for carbon steel in different atmospheres

Abstract

Sulfonated corrosion inhibitors have been used to protect materials in in-door or out-door storage temporarily. However, the use of environmentally friendly inhibitors becomes a necessity to reduce the environmental impact. In this work, fatty amides and anionic fatty surfactants were synthesized from inedible coconut and palm oil. These active compounds were formulated in natural wax and synthetic oil as vehicles of the anticorrosive formulation. The fatty amides were characterized by FTIR and NMR Spectroscopies. The corrosion behavior of carbon steel covered with these inhibitors was compared with the action of two marked products sulfonate base. Quantification of accelerated corrosion testing of preventive inhibitor coated evaluation was made by weight loss measurements after exposure in a fog chamber, simulating four types of atmospheres, namely marine, industrial-marine, rural and rural polluted. It was found fatty amide inhibitor from palm oil reduces corrosion rate efficiently for carbon steel protecting in rural environment 336 h with a 98.4% of efficiency and for a polluted rural environment 168 h (98.8%) in fog chamber. For Prohesion cyclic conditions, the temporary protective layer regularly used to protect until 244 h with 99.8% of efficiency. XRD patterns of rust samples revealed the presence of Fe 3 O 4 as the main phase in the film. The SEM micrographs showed that the fatty amide base coating presented an excellent efficiency in the four proposed atmospheres. Finally, this work is the first evaluation study of fatty amides in conditions of accelerated corrosion in the fog chamber.