Effect of diesel on corrosion inhibitors and application of bio-enzyme corrosion inhibitors in the laboratory cooling water system

• Diesel negatively affects corrosion inhibition performances of chemicals and bioenzymes.
• Optimal combined inhibitor has trimethylene phosphonic acid, lysozyme and laccase.
• Combined inhibitor has good performance at pH being 7–9 and temperature being 30–70 °C.
• Combined inhibitor has a wider tolerance of organic substances and Ca2+.

Negative effects of diesel on corrosion inhibition performances of 1-hydroxy ethylidene-1, 1-diphosphonic acid (HEDP), amino trimethylene phosphonic acid (ATMP), lysozyme and laccase were investigated. Orthogonal array design (OAD) was used for achieving the optimal composition of a combined inhibitor. The applied conditions of the combined inhibitor were also optimized. The results show that diesel can badly affect corrosion inhibition performances of HEDP, ATMP, lysozyme and laccase. The optimal combined inhibitor consisting of 30 mg/L ATMP, 30 mg/L lysozyme and 40 mg/L laccase can make the corrosion rate of carbon steel below 0.0075 mm/y and the corrosion inhibition efficiency above 96%.

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