Lignosulfonates Compound Application Performance Scale And Corrosion Inhibitor

Sodium lignosulfonate is separated from the byproduct of papermaking, with its merits of low price, convenient sources and no pollution, it once used as the corrosion and scale inhibitor, but its ability of inhibition isn't very good and lack of stability, since these limitation, sodium lignosulfonate replaced by phosphate water treatment agentia. Based on studying the corrosion and scale inhibition performance of sodium lignosulfonate, this paper choose HEDP, ATMP, sodium tripolyphosphate, hexamethylene tetramine and zinc chloride to compound with sodium lignosulfonate. By the test, ATMP and zinc chloride were selected to prepare the new corrosion and scale inhibitor SLA, the ratio of preparation was determined considering performance and environmental protection, with an analysis for the corrosion and scale inhibition mechanism being the first step. The result of the experiment shows:The calcium carbonate scale inhibition ratio of SLA is 95.48% when concentration is 20mg/L, in the same concentration, the scale inhibition ratio of sodium lignosulfonate is only 24.15% and the ratio of ATMP is 90.16%. When the concentration of SLA is 25mg/L, the calcium sulfate scale inhibition ratio is 55.14%, ATMP takes second place, the ratio is 38.54%, the scale inhibition ratio of sodium lignosulfonate is only 5.65%. The research on scale inhibition performance of calcium phosphate shows that the scale inhibition ratio of SLA reaches 50.61% when concentration is 25mg/L, the ratio of ATMP is 30.24%, the scale inhibition ratio of sodium lignosulfonate is the lowest, only 13.01%. With the temperature, rigidity and alkalinity rising, the scale inhibition performance of SLA is dropped. Fe³⁺ existing in solution is bad for scale inhibition, however Cu²⁺ and SLA can possess synergistic effect.This paper uses the weight loss method to determine the corrosion inhibition performance of SLA, it is found that SLA has better effect of corrosion inhibition on pre-filming carbon steel, the corrosion inhibition ratio is over 90% when the concentration is 60mg/L, but if it wanted to achieve the same ratio, the carbon steel sheet of void pre-filming need 100mg/L. The corrosion inhibition ratio of SLA keeps steady state as raising concentration in other pH except in more acid circumstance of pH5. The effect of corrosion inhibition to stainless steel is good, with concentration rising, the corrosion inhibition ratio of SLA goes up, and approaches to 100%. However, the corrosion inhibition ratio of SLA to brass and aluminum rise first and then fall, when concentration is 60mg/L, the maximum ratio is 90.54% and 79.27% respectively. When the corrosion experiment is run in the simulating cooling water and pre-filming is void, SLA can accelerate the corrosion of carbon steel in low concentration, it is knowed that this phenomenon due to the presence of CaCl₂ and NaHCO₃. The static corrosion inhibition ratio is inferior to dynamic condition.It uses the sodium lignosulfonate, SLA and hexamethylene tetramine as the acid-washing restrainer, as well as checking the effect of running time in the corrosion inhibition performance by the experiment. It is found that the performances of sodiumlignosulfonate and SLA aren't very good when solely used, but they behave better after compounding with hexamethylene tetramine. The curves of inhibitors' corrosion inhibition ratio keeps step basically in the 4 and 8 test hours, so the different running time doesn't affect corrosion inhibition ratio during the acid-washing time.It is showed that SLA is a corrosion inhibitor with model of adsorbing membrane, its scale inhibition action against scaling substance in solution is due to synergistic effect of chelation function, dispersion function and crystal lattice distortion function.