Development And Evaluation Of The Corrosion Inhibitor For Mud Acid Cleaning Of Galvanizing Equipment

Zinc is one of the important non-ferrous metals in industry and common life, which was often used in anti-corrosion coating protection of metal and electrochemical anodic protection of equipment.With the development of modern industry, agriculture and aquaculture, the use of galvanized equipment, especially the processing of galvanized Evaporative cooler for agricultural products and refrigeration and heat exchanger for aquatic product processing and storage, are increased hugely.In the process of running these galvanized heat exchange equipment, the impurities in the medium(mostly water) deposition and scaling can decrease the equipment in the thermal efficiency, even let it unable to run.The best way to remove fouling is chemical cleaning, with useing the effective cleaning agent of hydrochloric or mud acid.The development of acid cleaning inhibitor for galvanized equipment is very difficult, as the corrosion resistance of zinc in acid level is 10, which means zinc is one of the most not corrosion of metal materials with low electrode potential(phi ? = 0.7628 V) and K? = 5.888×1025 for zinc and acid reaction equilibrium constant.It is hard to keep the zinc coating from corrosion for the galvanized equipment coating is very thin, even if the zinc corrosion efficiency up to 99% above.Combined with it is susceptible to macro galvanic corrosion during the steel exposed in equipment, the development of acid cleaning inhibitor for galvanized equipment is even difficult.It has successfully developed several domestic hydrochloric acid cleaning inhibitors for galvanized equipment, while the practical value of mud acid cleaning inhibitor for galvanized equipment has not been reported both at home and abroad.Herein, the zinc corrosion performance of a large number of compounds in 2.5% mud acid solution under the normal temperature was studied. It is shown that the aldehyde, heterocyclic compounds and quaternary ammonium salt has good corrosion effect for zinc in the mud acid.A large number of experimental results show that the synergistic effect on inhibition of one-component between aldehyde and amine has the very good effect. Four kinds of amine(SA), triethanolamine [N- methyl diethanolamine(NA), aniline(BA), o-phenylendiamine(LA)] and four kinds of aldehyde [salicylic aldehyde(SQ), benzaldehyde(BQ), furfural(KQ), cinnamaldehyde(RQ)] synergies between the best.To evaluate a two-component corrosion inhibitors, the effects of the 16 aldehydes and amine groups were studied using weight loss method and electrochemical method, and the corrosion mechanism is analyzed at the same time.Mud acid medium, zinc in under the action of different concentration of amine and aldehyde, its corrosion rate gentle erosion efficiency diagram, confirmed that amine and aldehyde happened very good effect, the synergistic effect and mixed amine and aldehyde is the best ratio. Electrochemical polarization curves showed that the join of aldehyde amine and corrosion inhibitors compared with single aldehyde or amine as a corrosion inhibitor, corrosion potential is move, and significantly reduce the corrosion current. The composite corrosion inhibitor is cathode inhibited type, which is a secure corrosion inhibitor. The corrosion inhibition of this kind of corrosion inhibitors is due to the adsorption or overlap among aldehyde on the oxygen in the lone electron pair or amine, as well as the PI schiff base electronic cross the zinc surface.By multi-component compound corrosion inhibitor, identify the best combination of corrosion inhibitor ingredients, using orthogonal experiment method to obtain the optimal proportion between corrosion components, thus developed a highly efficient galvanized equipment JZL mud acid cleaning corrosion inhibitors, and the corrosion inhibition performance was evaluated. It shows that the corrosion inhibitor corrosion rate can be as high as 99.9% above with the inhibitor, and the corrosion rate of zinc fells to 0.15g·m-2·h-1, indicating that the inhibitor has high efficiency of the corrosion. The corrosion inhibitor has good anti-jamming performance, the corrosion rate of zinc is less than 0.4 g·m-2·h-1, with the case that acid concentration in soil is less than 6%. Under 40 ℃, the zinc corrosion rate is only 0.27 g·m-2·h-1; No corrosion inhibitor failure phenomenon was found in 24 hours. JZL electrochemical research results show that the corrosion inhibitors is a kind of cathode inhibition of mixed corrosion inhibitor, which makes zinc corrosion current decreased greatly. The corrosion inhibitor dosage of JZL is small, nonpoisonous and harmless, with high efficiency and strong anti-interference, which do not produce non-uniform corrosion phenomenon. JZL is a kind of environmentally friendly efficient mud acid cleaning inhibitor for galvanized equipment, which has the very good application prospect.