How to determine the concentration of tonifying liquid?
In order to prevent rust and improve the anti-corrosion performance of phosphating film during the process, passivation treatment is often carried out after metal cleaning or phosphating. The traditional passivation agent is sodium dichromate or chromic anhydride. Public nuisance has been eliminated. This method uses two chromium-free passivating agents, PAR_COLENE90 and DEOxYLYTE54NC provided by Henkel, Germany, and the introduction is as follows.
1 PARCOLENE90 chromium-free passivation agent
This product is a chrome-free post-treatment chemical specially used for zinc phosphate conversion coatings in the automotive industry, and can be used for both spraying and dipping. After treatment, the corrosion resistance of the metal surface after conversion coating can be enhanced, and the concentration is 13~19 points, and the pH value is 5.0~6.0.
(1) Determination of concentration:
For the H2s04 solution, use a 50mL titration tube with bath solution to carry out the titration, so that the pink color disappears and becomes orange-yellow as the end point.
(2) Determination of pH value: Use a glass electrode pH meter for measurement, and the sensitivity of pH test paper is poor.
2. DEOXYLYTE54NC chromium-free passivator
This product is an acidic chromium-free liquid chemical for the final rinse of phosphating-treated metal surfaces. It can be sprayed or dipped. After treatment, it can improve the adhesion of paint coatings and prevent corrosion and blistering under the coating. phenomenon is greatly reduced. The process controls the total acid volume to be 4.0~6.0mL, the pH value to be 4.0~4.5, the concentration to be 1.5kg/1000L, and the temperature to be 20~55℃.
(1) Determination of total acidity: transfer 100mL of water into a 300mL beaker with a pipette, add 6-10% phenolic indicator, and determine with 0.1mol/L NaOH until the color turns pink, and keep for 30s. The total acid volume is 4~4.6mL.
(2) Determination of pH value: Rapid determination can be made with pH test paper or electronic pH measuring instrument.
