Plastic plating-A brief introduction to the analysis of coarsening solution for ABS plastic plating.
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1 preface.
The coarsening process of plastic electroplating makes the plastic surface achieve micro-roughness, changing from hydrophobicity to hydrophilicity, so as to improve the adhesion between the surface and the coating. Accurately grasping the content of each component in the coarsening solution is beneficial to the adjustment, maintenance and control of the coarsening bath, and is very important for the whole process of plastic electroplating. At present, the high chromic acid coarsening solution with fast coarsening speed and good effect is mostly used in plastic plating production line, and its composition range is generally [1]: H2SO4 330g / L, CrO3 400g / L 430g / L, or H2SO4 600g / L, CrO3 250g / L 350g / L.
Through analysis and test, the author has developed an analysis method of high chromic acid coarsening solution, which has had a very good effect on the maintenance, adjustment and control of coarsening bath solution since the establishment of plastic electroplating production line.
2 Analysis method.
2.1 H2SO4 content analysis.
2.1.1 principle of method.
The Pb (NO3) 2 solution added to the analytical sample reacted with CrO2-4 and SO2-4 to form PbCrO4 precipitation and PbSO4 precipitation, and quantitative H + was precipitated. The sample solution was titrated with NaOH standard solution, and the H2SO4 content in the coarsening solution was calculated.
2.1.2 Reagent.
W (Pb (NO3) 2) = 20% Pb (NO3) 2 solution, c (NaOH) = 1 mol/ L NaOH standard solution, w (methyl orange) = 1% methyl orange indicator.
2.1.3 Analysis steps.
Take 1 mL coarsening solution in a 250 mL beaker and slowly drop warm (< 45 ℃) Pb (NO3) 2 solution under continuous shaking until the yellow of the upper supernatant disappears completely and is colorless. Filter in 300mL triangular beaker with two layers of filter paper, wash the precipitation with warm water for several times, cool the filtrate to room temperature and add 1 drop methyl orange indicator, titrate with NaOH standard solution until the solution changes from red to orange as the end point.
2.1.4 calculation.
ρ (H2SO4) / (g / L) = c × V × 5016 / V0-ρ (CrO3) × 1.0112.
In the formula: the concentration of the amount of substance in the c-NaOH standard solution / (mol/L).
Volume / mL of NaOH standard solution consumed in V-titration.
Volume / mL of coarsening solution taken during V0-titration.
Mass concentration of CrO3 in ρ-coarsening solution / (g / L).
1.0112-CrO3 is converted to the conversion factor of H2SO4.
2.1.5 this method is compared with the traditional method (gravimetric method).
This analysis method is simple, fast and high accuracy. it solves the problem of poor accuracy when the traditional method consumes a long time and high content, plays an important role in the maintenance, control and adjustment of trough liquid, and achieves excellent results in practical production.
2.2 content analysis of CrO3 and Cr2O3.
The content analysis method of CrO3 and Cr2O3 in coarsening solution is the same as that of CrO3 and Cr2O3 in chromium plating solution. This method is also suitable for high sulfuric acid coarsening solution [1].
3 conclusion.
This method is practical, simple, fast and accurate. In the process of application, it guides the production timely and accurately for many times, achieves satisfactory results in the maintenance, adjustment and control of coarsening bath, and plays an important role in the whole process of plastic electroplating.
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