This chapter studies the operational parameters effects, such as immersion time, corrosion products, and pH, on the inhibition efficiency against corrosion for low carbon steel in simulated cooling water system of the mixture 1 (10-3 M 3-MPOX + 20 ppm CTAB), which corresponds to the best inhibition efficiency. The results show that the corrosion inhibition performance of the studied mixture reinforces with immersion time and has a maximum in the pH range 6.5–7.5. In addition, the analysis of the results shows that there is a dependence of the pH value of the solution and the corrosion current density (icorr). Indeed, a correlation can be established between log (icorr) and the pH using the polynomial equation. Finally, the mixture 1 provides good protection for the attack materials. These studies were evaluated from the polarization curves (PP), electrochemical impedance spectroscopy (EIS).
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Steel is a material widely used in various industrial fields [Benarioua et al., 2019; Lafont et al., 1993; Abouchane et al., 2015]. It is found in cooling water systems because of their interesting properties including electrical and thermal conductivities high, good chemical weld ability and low cost. Despite these properties, this material may suffer a significant degradation whose forms and their characteristics differ according to several parameters: composition of the middle, temperature, pH, flow velocity...
The quality of the heat exchange in a cooling circuit is a crucial element. Scale, corrosion, and biocoorrosion affect the performance of the cooling process That is why researchers are currently working on the development of formulations of water treatment composed mainly of scale inhibitor, corrosion inhibitor, oxidizing and non-oxidizing biocide, Legionella, biodispersant and dispersants for mineral and organic matter [Abousalem et al., 2019; Ramesh et al., 2004].
For instance, in our recently papers [Rochdi et al., 2014, 2015], the oxadiazoles derivatives effect on corrosion and scale inhibition of brass and low carbon steel in simulated cooling water was compared. It was found that these compounds acte as mixed inhibitors-type and their inhibition efficiency depended on their molecular structure of the oxadiazoles compounds and more precisely on the position of the methyl group in the cycle. Indeed, the sequence of the undertaken oxadiazole inhibitors is then, 3-MPOX ≥4-MPOX >2-MPOX. In addition, their inhibitions were enhanced by the non-oxidizing biocide CTAB addition. So, a large plate of passivation (about 500 mV/SCE of wide) was registered in the case of mixture 1 (10-3 M 3-MPOX + 20ppm CTAB) which reinforced the low carbon steel or brass resistance against pitting corrosion.
The originality of this work lies in the fact that the proposed formulation protects both the low carbon steel as brass [Rochdi et al., 2014, 2015] and therefore can be used in a cooling system constitutes, as is the case in general, the two materials. In such a case, the industrial use of formulations containing two inhibitors; one for the brass and the other for the steel.
Scheme 1. Cooling water Triangle
Scheme 2. SEM micrographs of copper electrode surface after immersion in cooling water solution: (a) the blank solution and (b) the presence of mixture VATP and biocide CTAB
[Ramesh et all., 2004].