Applied Study on Composite Type of Industrial Corrosion and Scale Inhibitor

Applied Study on Composite Type of Industrial Corrosion and Scale Inhibitor Preparation with Hot Acid Treated Attapulgite ClayHan Hong1,2, Gu Xu1,2, Li Dong1,2, Zhu Mingbo21 Key Laboratory for Palygorskite Science and Applied Technology of Jiangsu Province, Huai’an, Jiangsu, 223003, China;2 College of Life Science and Chemical Engineering , Huaiyin Institute of Technology, Huai’an, Jiangsu, 223003, Chinanznidy@Abstract—A new composite type of industrial corrosion and scale inhibitor of maleic anhydride-acrylamide copolymer attapulgite was developed, when water was solvent, hydrogen peroxide was initiator, maleic anhydride (MA) and acrylamide were monomers, and hot acid treated attapulgite clay was added into the polymerization system. Its scale and corrosion inhibitions were evaluated by methods of static test and rotary weight loss test. For further study, modification temperature and acidity, stirring time, and adding dosage of attapulgite clay on the scale inhibition performance of copolymer were investigated, as well as the corrosion inhibitory property of the final product. Results showed that, the copolymerization conditions were: modified attapulgite clay after 300 ℃calcination and 4% hydrochloric acid 0.05 g, maleic anhydride 2.7 g, acrylamide 1.525 g, hydrogen peroxide 1 mL, water 9.9 mL, reaction temperature 60 ℃, and stirring time 100 min. Under these conditions, the hightest anti-scaling rate was 85.68% that was improved by 73.40%, and the corresponding corrosion rate was 0.093 mm/a that was improved by 26.2%. The composite type of industrial corrosion and scale inhibitor prepared with hot acid treated attapulgite clay possesses advantages of new-type, efficient, economical and phosphate-free, and proves potential application prospect in industrial circulation cooling water treatment.Keywords-Attapulgite Clay; Hot Acid Treatment; Corrosion and Scale Inhibitor; Circulation Cooling WaterI.I NTRODUCTIONAt present, in the industry of electricity and steel homeand abroad, organophosphorus water quality stabilizers such as HEDP, ATMP, PBTCA and HPAA that have smallmolecules and high phosphorous contents are universally adopted in antiscaling and anticorrosion of industrial circulation cooling water system. The phosphorous content is as high as 12.0%-32.0%. On the one hand, it gives rise to excessive growth of bacteria and algae in the cooling equipment; on the other hand, the discharge water brings about eutrophication to the environment. Thus, water quality stabilizers with low-phosphorous or non- phosphorous have attracted more and more attention [1]. As for the elements of cost and dosage, and undesirable antiscaling and anticorrosion effects, the non-phosphorous water quality stabilizer is still in growing phase. Attapulgite clay is a natual crystalline non-metallic clay mineral, containing aquated aluminum and magnesium silicate. It has special fibre structure, unique colloidal properties of dispersion, heatresistance, salt and alkali toletance, as well as favourbleplasticity and cohesion, and excellent adsorbability, so exhibits wider application prospect in water treatment field[2]. The present data stated that there was rare report on the preparetion of corrosion and scale inhibitor with attapulgite clay and organic copolymer synergistically combining.In this study, a new composite type of industrialcorrosion and scale inhibitor of maleic anhydride-acrylamide copolymer attapulgite was developed, whenwater was solvent, hydrogen peroxide was initiator, maleic anhydride (MA) and acrylamide were monomers, and hot acid treated attapulgite clay was added into thepolymerization system for promoting antiscaling and anticorrosion properties. It aimed at providing a new-type, efficient, economical and phosphate-free composite corrosion and scale inhibitor.II.MATERIALS AND METHODSA.Principle of bi-copolymerizationThe bipolymer based on maleic anhydride (MA) and acrylamide was one of the early developped corrosion andscale inhibitor of copolymer type. The principle was that anhydride (MA) and acrylamide as monomers polymerized by the fuction of initiator, then hydrolyzed, and the producthydropolymaleic anhydride (HPMA)-acrylamide was obtained [3]. In the flask that was equipped with mechanicalrabbling, reflux condenser, drop funnel and thermometer, a certain amount of maleic anhydride (MA) , acrylamide anddistilled water were mixed; then hydrogen peroxide was added by dropwise into the flask while stirring for 20-30min. Then the reaction was kept by heat preservation for 1.5 h, stopped and cooled. In this way, a white or wheat thick liquid, hydropolymaleic anhydride (HPMA)-acrylamide copolymer was prepared.B. Materials and analytical methods1) Main drugsAcrylamide (CP), maleic anhydride (AR), hydrogen peroxide (30%), calcium chloride (AR), sodium bicarbonate (AR), sodium hydroxide (AR), EDTA (AR), calconcarboxylic acid, sodiumchloride (AR), deionized water, attapulgite clay (raw ore, Xuyi, Jiangsu Province), hydrochloric acid.2) Main instruments2011 International Conference on Computer Distributed Control and Intelligent Environmental MonitoringThermostatwaterbath, mechanical agitator, droppingfunnel, thermometer, reflux condenser, centrifuge, drycabinet, retort, corrosion apparatus (ZJ Type). 3) performance measurement of copolymer [4]a) Scale inhibition performance: static evaluation test（GB-T 16632-2008）Simulative circulation cooling water was prepared usingdeionized water as solvent, and ρ（Ca2+）=0.7 g/L ，ρ（HCO3-）=0.35 g/L. EDTA complexometric titrationmethod was used for determination of Ca2+ content. Theanti-scaling rate was calculated as fomula (1): anti-scaling rate = (V1-V0) / (V2-V0) × 100% (1) in which ：V0—— without copolymer ，dosage of EDTA after constant temperature (mL); V1——with copolymer ，dosage of EDTA after constant temperature (mL); V2——blank value, dosage of EDTA at room temperature (mL). b) Corrosion inhibition performance: rotary weight loss test （GB-T18715-2000） Corrosion rate (η) was meatured by gravimetric method using 20# carbon steel. It was indicated with degree of corrosion annually, and was calculated as fomula (2):η= 87.6 × (w1-w0) / (S×T×7.85) (2) in which: w1——weight of test block before experiment (mg); w0——weight of test block after experiment (mg); S——total surface area of test block （cm2）; T——storage period of test block （h ）; 87.6——conversion coefficient ; 7.85——density of carbon steel (g/cm3) . C. Preparation methods of composite corrosion and scaleinhibitor1) Modification of attapulgite claya) The refining flowchart of raw attapulgite clay wasas follows:Final productb) Hot acid treatmentHot treatment ：Attapulgite clay after refinement wasroasted at a certain temperature for 4 h, then cooled ；Acid treatment: Attapulgite clay after hot treatmentwas added into a certain concentration of hydrochloric acid,at a solid-to-liquid ratio of 1:10. Stirred for 2 h at 200 r/min,then filtered and dryed.2) Synthesis experiment with modified attapulgite claya) Weighed 0.1 g refined attapulgite clay, conductedhot modification temperature at 200 ℃, 300 ℃, 400 ℃, 500 ℃, 600 ℃, respectively, then put it into the synthetic reaction system when maleic anhydride (MA) and acrylamide had totally dissolved, then dropped hydrogen peroxide, copolymerized. Measured the anti-scaling rate. Thus the best modification temperature was drawed. b) Weighed 0.1 g refined attapulgite clay after hotmodification at optimal temperature, put in into hydrochloric acid for acid modification at mass fraction of 2%, 3%, 4%, 5%, 6%, respectively. Then put it into the synthetic reaction system following a). Thus the best modification acidity was drawed. c) Varied stirring time of copolymerizing at 20 min, 40 min, 60 min, 80 min, 100 min, 120 min ，respectively. Put the modified attapulgite clay at best temperature and acidity into the synthetic reaction system following a). Thus best stirring time was drawed. d) Varied the dosage of modified attapulgite clay at0.025 g, 0.050 g, 0.100 g, 0.125 g, 0.150 g, respectively.Then put it into the synthetic reaction system following a).Thus the best dosage of modified attapulgite clay wasdrawed.e) Measured corrosion rate of the copolymer before and after the addition of attapulgite clay, respectively. Compared the effect of attapulgite clay on corrosion inhibition performance. III. RESULTS AND DISCUSSION By the single factor method, the determined bi-copolymerization conditions were: maleic anhydride (MA)2.7 g, acrylamide 1.525 g, 30% hydrogen peroxide 1 mL, water 9.9 mL, reaction temperature 60 ℃, reaction time 2 h, under which the available anti-scaling rate was 55.82% and the corrosion rate was 0.126 mm/a. Then the effect of attapulgite clay addition on corrosion and scale inhibitionperformance was further investigated, maintaining the above conditions. A. Hot treatment of attapulgite clay on scale inhibition performance Attapulgite clay by hot treatment at diffetrent temperatures was feeded, Graph 1 showed the scale inhibition performance. It was clear that, scale inhibition performance enhanced with the increasing of temperature;When it reached 300 ℃, the anti-scaling rate peaked at 76.54%, then after it began to decrease, at the point of 500 ℃, it approached to a flat. In low temperature range, zeolitic water and crystal water of attapulgite clay were partly deprived with the increasing of temperature [5], which enlarged the contract area of particle surface with organics, and improved graft copolymerization efficiency; When the temperature exceeded 400 ℃, the pore canal of attapulgite clay showed folds and the exchange and adsorption abilities with organics were weakened, thus graft copolymerization efficiency decreased. At 600 ℃, the anti-scaling rate wasdistinctly low, which resulted from further decline ofspecific surface area. Table 1 showed the relationship between specific surface area of attapulgite clay and modification temperature. Therefore, 300 ℃ was chosen as hot modification temperature.A n t i -s c a l i n g r a t e / %Tem per atur e / ℃Figure 1. Hot treatment temperature of attapulgite clay on scale inhibitionperformanceTABLE I.SPECIFIC SURFACE AREA OF ATTAPULGITE CLAYAFTER HOT TREATMENTHot Treatment Temperature（℃） Specific Surface Area（m2/g ） 200 124.3 300 128.9 400 119.0 500 81.68 60064.87B. Acid treatment of attapulgite clay on scale inhibition performanceAttapulgite clay by acid treatment at diffetrent acidities of hydrochloric acid was feeded, Graph 2 showed the scale inhibition performance. It was visible that, scale inhibition performance enhanced with the increasing of acidity; When the acidity reached 4%, the anti-scaling rate peaked at 76.54%, then after it began to decrease. The adsorption property of attapulgite clay was conditioned by micro crystal structure. It mostly presented that, substance that was adsorbed by the internal surface of attapulgite clay must have a molecular diameter less than that of the pore canal. While after acid treatment, the contents of Mg, Al, K, Fe in attapulgite clay sharply reduced, and impurities that inside the pore canal were cleared up; At the mean time, H+ replaced Mg2+、Al3+、K+ and Fe2+ inside the layer, which expanded pore allowance and weakened bonding forces between layers, thus the crystal lattice cracked, the pore canal was more dredged, and the abilities of adsorption and graft copolymerization with organics reinforced. When the acidity was relatively low, the octahedron cation was partly soluted, and most silicon-oxytetrahedron retained, and the aggregation of Si-OH functional group on the surface inproved its surface performance greatly; then as the acidity increased, crystal structure was damanged, which blocked the graft copolymerization and lowered the anti-scaling rate correspondly. Therefore, 4% of hydrochloric acid was chosen as acid modification acidity.C. Stirring time on scale inhibition performanceStirring time of copolymerization process was varied, Graph 3 showed the scale inhibition performance. It could be seen that, scale inhibition performance enhanced with the increasing of stirring time; When the stirring time was 100min, the anti-scaling rate peaked at 77.68% , then after it began to decrease. With the increase of stirring time, attapulgite clay had been able to fully contact with the organics, and the organics entered into the pore cannal for adsorption and graft copolymerization; Moreover, the special decentrality of attapulgite clay enabled it disperse rapidly in the reaction system, its favourable adsorption and adhesion stress abilities rendered it adsorb Ca2+ in the solution effectively, and the positive charge in its surface could also substitute with Ca2+, thus the anti-scaling rate was augmented. But, if the stirring time was too long, the copolymer mightdestablize and influence the anti-scaling rate. Therefore, 100 min was the balance point of adsorption and copolymerization, and it was the chosen stirring time.304050607080A n t i -s c a l i n g r a t e / %A cid it y / %Figure 2. Acid treatment acidity of attapulgite clay on scale inhibitionperformance1020304050607080A n t i -s c a l i n g r a t e / %Stirring time / minFigure 3. Stirring time on scale inhibition performanceD. Dosage of attapulgite clay on scale inhibition performanceDosage of modified attapulgite clay was varied, Graph 4 showed the scale inhibition performance. It was distinct that, when the dosage was less than 0.05 g, scale inhibition performance enhanced with the increasing of dosage notably, When the dosage was 0.05 g, the anti-scaling rate peaked at 85.68%; then after it began to decrease, after 0.1 g the downtrend was obvious. This was because graft copolymerization between attapulgite clay and organics existed the saturation adsorption quantity; if it was exceeded, the redundant attapulgite clay would suspend in the copolymerization system and solutions, which interferenced with the scale inhibition performance of the copolymer, and that, superfluous attapulgite clay might form residua that was hard to clean. Therefore, the chosen dosage of attapulgite clay was 0.05 g.12345678910A n t i -s c a l i n g r a t e / %Dosage of attapulgite clay / gFigure 4. Dosage of attapulgite clay on scale inhibition performanceE. Corrosion inhibition performance evaluation of composite systemThe coupon was submerged into test water with corrosion and scale inhibitor at (45±1) ℃, using the copolymer with and without attapulgite clay, respectively. After 72 h, it was taken out and weighted. When the corrosion rate leveled off, the corrosion rate was 0.126 mm/a and 0.093 mm/a before and after addition of attapulgite clay, respectively. Corrosion inhibition performance was improved by 26.2%. It was demonstrated that attapulgite clay benefited on the corrosion inhibition performance. Silicate has been applied in corrosion inhibition of steel for about 60 years, it was rich in resources, non-toxic, cheap and bacteria breed prevented. It can form deposited film on the surface of the metal and prohibit corrosion [6]. When modified attapulgite clay and organics copolymerized into organosilicate, on the one side, it made up the weakness that corrosion inhibition performance of phosphate-free organic copolymer was non-ideal; on the other side, it overcomed the shortcoming that inorganic silicate was apt to form silicate scale. It realized phosphate-free in circulation cooling water treatment.F. Probe into mechanismThe adsorption of maleic anhydride–acrylamide copolymer on calcium carbonate microlite was mono-molecular chemical adsorption and accorded with Langmuir isothermal adsorption, which took effect in inhibition of crystal growth [7]. The scale inhibition effect gave priority to adsorption, accompanied by deformation, dispersion, solubilization, chelation and so on [8]. When the composite inorganic-organic copolymer was prepared by graft copolymerization of modified attapulgite clay and organics, it generated synergistic effect with the original organic copolymer. The special decentrality of attapulgite clay enabled it disperse rapidly in the reaction system, its favourable adsorption and adhesion stress abilities rendered it adsorb Ca2+ in the solution effectively, and the positive charge in its surface could also substitute with Ca2+, thus the anti-scaling rate was augmented. At the same time, attapulgite clay was a kind of inorganic silicate clay mineral and could form deposited film on the surface of the metal itself, which made up the weakness that corrosion inhibition performance of phosphate-free organic copolymer was non-ideal, and enhanced the corrosion inhibition performance of the copolymer.IV. CONCLUSIONS1) It was feasible when water was solvent, hydrogen peroxide was initiator, maleic anhydride (MA) and acrylamide were monomers, and hot acid treated attapulgite clay was added into the polymerization system for promotion of corrosion and scale inhibition of the product; And the conditions of copolymerization were: 300 ℃calcination and 4% hydrochloric acid with attapulgite clay for pretreatment , dosage of modified attapulgite clay 0.05 g, and stirring time 100 min, under which the maximun anti-scaling rate was 85.68%, improved by 53.5%, and at this point, corrosion rate was 0.093 mm/a, improved by 26.2%. 2) Attapulgite clay had special fibre structure, unique colloidal properties of dispersion, heatresistance, salt and alkali toletance, as well as favourble plasticity and cohesion, excellent adsorbability, and definite corrosion inhibition performance. When the composite inorganic-organic copolymer was prepared by graft copolymerization of modified attapulgite clay and organics, it generated synergistic effect with the original organic copolymer.3) The composite type of industrial corrosion and scale inhibitor prepared with hot acid treated attapulgite clay possesses advantages of new-type, efficient, economical and phosphate-free, and proves potential application prospect in industrial circulation cooling water treatment.A CKNOWLEDGMENTAuthors would like to thank Huaiyin Institute of Technology, and Young Teacher support program, who financed this study.R EFERENCES[1] Dong-jin C. Development of an environmentally safe corrosion, scale,and microorganism inhibitor for recirculating cooling systems. Materials Science and Engineering, 2002, 335:228-236.[2] Ahmed, Al-Futaisi, Amer Al-Rawas and Saif Al-Hanai. Adsorptioncapacity and mineralogical and physico-chemical characteristics of Shuwaymiyah palygorskite (Oman). Environ Geol, 2007, 51:1317-1327.[3] Zhou Bensheng. Technology in industrial water treatment. Beijing:Chemical Industry Press, 1997. (in Chinese)[4] Analysis and experiment methods of cooling water by ChinaPetroChemical Corporation. Beijing: Petroleum Industry Press, 1989. (in Chinese)[5] Mark P.S. Krekeler and Lance E. Kearns. A new locality ofpalygorskite-rich clay from the southeastern Yucatan: a potential material source for environmental applications. Environ Geol, 2009, 58:715-726.[6] Larry W Beeker. High calcium to tolerant deposite control method.US:4479878, 1984.[7] M.M. Reddy and G.H. Nancollas. The crystallization of CalciumCarbonate II, Calcite Growth Mechanism. J.Coll.and Interfac.Sci., 1971, 37:824-830.[8] Marentette J.M., Norwig J. and Stockelmann E.. Crystallization ofcalcium CaCO3 in the presence of PEO-block-PMAA copolymers. Advanced Materials, 1997, 9:647-653.。