Acidic Medium, A New Nitrogen-containing Corrosion Inhibitor For Carbon Steel Corrosion Inhibition

This paper synthesized two mannichbase corrosion inhibitors. The raw materials of first inhibitor are acetone, aldehyde and diethylamine, named ZD-1; the raw materials of second inhibitor are acetone, aldehyde and hydroxylammonium chloride, named ZD-2. Experiments show that two mannichbases have corrosion inhibition on Q235 steel when in acid medium. In order to improve the corrosion inhibition efficiency, the writer also laid emphasis on the research of the corrosion inhibition of corrosion inhibitors together with halogen ions and surfactant complex on Q235 steel which was in acid medium.The main methods of research are:immersion test, potentiodynamic scanning, EIS. The writer researched the Q235 steel's corrosion in acid medium which contain different corrosion inhibitors, and also the Q235 steel's corrosion in acid medium with same corrosion inhibitor at different temperatures. Corrosion inhibitors species are: ZD-1,ZD-1-KCl,ZD-1-KBr,ZD-1-SDS,ZD-1-SDS-KCl,ZD-2,ZD-2-KCl,ZD-2-KBr,ZD-2-KI. The results from above three methods are consistent, and the relations between corrosion inhibition efficiency and corrosion inhibitor are:(1)ZD-1-KBr>ZD-1-SDS>ZD-1-KCl>ZD-1-SDS-KCl>ZD-1; (2)ZD-2-KI> ZD-2-KBr>ZD-2-KCl>ZD-2; (3)ZD-2>ZD-1; ZD-1-KCl>ZD-2-KCl; ZD-l-KBr >ZD-2-KBr. Temperature experiment showed that the two mannichbase corrosion inhibitors can adapt wide temperature range, and has little effect when temperature changed.According to polarization curve, ZD-1 is cathodic corrosion inhibitor; ZD-1-KCl and ZD-1-KBr are cathode-controlled mixed type corrosion inhibitors; ZD-1-SDS and ZD-1-SDS-KCl are mixed type corrosion inhibitors; ZD-2 and ZD-2-KCl are cathodic corrosion inhibitors; ZD-2-KBr iscathode-controlled mixed type corrosion inhibitor; ZD-2-KI is mixed type corrosion inhibitor.Nyquist graph in EIS reflects the change rule of corrosion inhibition efficiency along with concentration change. Fitting the Nyquist graph by Zsimp Win, the relevant equivalent circuits and electrochemistry parameters are obtained. By these three methods, this paper researched the corrosion inhibition mechanism of the two mannichbase corrosion inhibitors and mixtures in-depth. Adsorption models from fitting are:ZD-1 adsorption accorded with El-Awady adsorption model; ZD-1-KBr, ZD-1-SDS-KCl, ZD-2, ZD-2-KCl, ZD-2-KBr and ZD-2-KI adsorption accorded with Frumkin adsorption model. Also, thermodynamical parameter was calculated in the paper. The conclusions provide theoretical basis for corrosion and protection of metals in the production practice.