Study Of Modified Potato Starch As Scale And Corrosion Inhibitor Performance

As more and more people tend to asses the scale and corrosion inhibitors from environment angle, research and development of the green scale and corrosion inhibitors is attaching more and more importance. Based on the analysis and generalization of the existent scale and corrosion inhibitors, a new scale and corrosion inhibitor called Oxidation Phosphate Potato Starch (OPPS) was modified from potato starch. The preparation condition on modifying was optimized through lots of single-factor experimental studies. Static scale and corrosion inhibition tests show that OPPS has better scale and corrosion inhibition properties. The scale and corrosion inhibition mechanism was also ratiocinated and researched.The condition of oxidation on potato starch are: weight ratio of starch (hydro-starch =5%) and NaIO₄ is 14500～14545; reaction time is 18～20h. The condition of oxidation on Double Aldehydes Potato Starch (DAPS) are: pH is between 4.5and 5.0, reaction time is 9.5～11h, ratio of H₂O₂ liquor (30%), NaClO₂ liquor (40%) is 3: 7.The condition of oxidation on Carboxyl Potato Starch (CPS) are: phosphate concentration (PO₄^3-) is 4.0%～5.0%; reaction temperature is 30°C～40°C; reaction time is 2～2.5h; pH is 5.0～7.0.OPPS is a composite inhibitor in which the main mechanism includes anode control. The corrosion inhibition mechanism is the dispersing, passivation, obstructing of the sedimentation membrane and absorbing membrane. Both membranes are brought up by the OPPS. The scale inhibition mechanism includes: crystal lattice aberrance, solubility augment of the scale, electrostatic exclusion.OPPS has nicer scale inhibition property. On certain condition that rigidity (CaCO₃) is 140.0— 144.4mg/L, pH is 8.3, temperature is 80°C, thescale inhibition can reach that of the ATMP on 4mg/L, also reach that of HEDP on 10mg/L. The tiptop of scale inhibition of OPPS can reach 78.59%. The optimal condition of single-factor scale inhibition tests contain: temperature is 70°C～80°C, concentration is 18mg/L～30mg/L, pH is 5.0～ 10.5, and rigidity (CaCO₃) is 100 mg/L～200mg/L.The optimal corrosion inhibition of OPPS on the condition of rigidity (CaCO₃) 100 mg/L～200mg/L and pH8.3 includes: corrosion inhibition to carbon steel can reach 91.25% on 80mg/L and 80°C; corrosion inhibition to copper steel can reach91.95% on 80mg/L and 70°C; corrosion inhibition to stainless steel can reach 92.78% on 20mg/L and 60°C; corrosion inhibition to aluminum can reach 91.57% on 80mg/L and 60°C.The optimal condition of single-factor corrosion inhibition tests contain: temperature =90°C, pH 5.0～10.5, rigidity (CaCO₃) = 200mg/L. Zinc is also a factor.In this experiment, the phosphorus concentration of the water is 0.312mg/L with maximum cast of OPPS is 200mg/L, under the limit(0.5mg/L) of the GB8978—1996 I on phosphorus.