Study On The Scale & Corrosion Inhibition Mechanism And Performance Of Tannic Acid

Each structural unit of tannin molecules includes polycyclic aromatic and activefunctional groups which embody phenolic hydroxyl group, hydroxyl and carboxy, etc. With avariety of active functional groups in the molecule, hydrophilia, surface active nature,ion-exchange, complexation and adsorption dispersing capacity are involved in tannic acidwhich can be used as scale inhibitor and corrosion inhibitor in water treatment applications.So it is very important to study and develop tannic acid.The capacity of scale and corrosion inhibition of tannic acid are researched with amethod of static-state scale inhibition, weight method and rotation specimen method. Firstly,the influencing factors of scale inhibition and corrosion inhibition of tannic acid are studied,such as scale type, temperature, alkalinity, hardness, metallic ion and specimen of differentmaterial. Secondly, PASP, PESA, ATMP, HEDP, HPMA and sodium gluconate are selected tocompound with tannic acid. Through the initial screening and orthogonal experiment design ,proportional allocation is defined. At the same time, tannic acid scale and corrosioncompound are obtained. Finally, we do research on scale and corrosion inhibition mechanismof tannic acid . The main conclusions are as follows:（1） Tannic acids have certain scale and corrosion inhibition. When dosage of tannicacids was 40 mg/L, the scale and corrosion inhibitions rate had reached 69.1% and 36.7%respectively.（2） Tannic acids applies to calcium carbonate scale in the situation of under the watertemperature of 70 degrees, low＆middle basicity and low＆middle hardness. Fe³⁺caninhibit scale inhibition of tannic acids, but Cu2+has synergistic effect.（3）With the temperature rising, the corrosion inhibition rate of tannic acid is dropped. It can be used in cooling systems that the temperature below 50℃. With pharmaceutical contentrising, the corrosion inhibition rate of tannic acid to H62 brass goes up. But to 1Cr18Ni9Ti, itrises first and then fall. When concentration is 40 mg/L , the corrosion inhibition rate to H62brass and 1Cr18Ni9Ti is 46.7% and 39.4% respectively.（4） The formula of tannic acid compound contains 15 mg/L tannic acid，15 mg/LPASP ,6 mg/L ATMP and 17.5 mg/L sodium gluconate. In cooling systems, its scale inhibition issignificant while the temperature below 80℃. Moreover, the best concentration is 8 mg/L ,and the scale inhibition reaches 100 %. In assition, Its corrosion inhibition is the best while thetemperature below 50℃. When the concentration is 50 mg/L, the corrosion inhibition rate is72.9 %.（5）The scale inhibition of tannic acid mainly be based on chelating function, crystallattice distortion function and dispersion function. Its corrosion inhibition primary depends onboth chemical adsorption and physical adsorption, so it possess definite corrosion inhibitingefficiency to metal.