Electroplating conductivity and potential changes of electric heating tubes

Electroplating conductivity and potential changes of electric heating tubes

The increase in Na3PO4 content leads to a decrease in colloid conductivity (Table 1), resulting in a higher conductivity when "4mol/LKOH+2% PAA+8% Na3PO4" becomes a colloid than when there are no additives. When J=75mA/cm2, the effect of Na3PO4 on aluminum potential is shown in Figure 3. Na3PO4 in colloidal electrolytes can improve the performance of Al anodes and enhance the discharge performance of aluminum.

Table 2 shows the effects of different additives on the electrochemical performance of Al anode.

The colloidal electrolyte containing 2% PVA and 8% Na3PO4 additives ("4mol/LKOH+2% PAA") has a significant improvement in polarization degree (see Figure 2), open circuit potential, electrode potential negative shift, discharge time, and other aspects compared to the absence of additives ("4mol/LKOH+25% PAA"). The effect of Na3PO4 is good.

Electroplating of aluminum and aluminum alloys is relatively difficult because aluminum has a strong affinity for oxygen and its surface is easily oxidized; Aluminum is an amphoteric metal that is unstable in both acids and alkalis; The potential of aluminum is very negative, and it is easy to be corroded and replaced by the plated metal in the electroplating solution; The expansion coefficient of aluminum is larger than that of most metals, so the coating is prone to bubbles and detachment, which affects the adhesion.

The key of aluminum and aluminum alloy electroplating is special pretreatment to remove the natural oxide film and prevent its re formation, and prevent the occurrence of single displacement reaction when aluminum parts are immersed in electrolyte. As a naval aircraft overhaul factory, we often encounter aluminum and aluminum alloy electroplating during the repair process. Through experiments, the optimal process conditions were explored. The surface of aluminum alloy coated parts not only has good glossiness, but also has excellent adhesion and corrosion resistance, meeting the requirements of navigation aids. This article introduces the electroplating process for repairing old aluminum alloy parts.

3 Conclusion

Adding 2% PVA and 8% Na3PO4 respectively can just make "4mol/LKOH+20% PAA" become colloids. Compared with "4mol/LKOH+25% PAA" colloidal electrolytes, the electrochemical performance of aluminum is greatly improved; In addition, 8% Na3PO4 has a more significant improvement in the electrochemical performance of aluminum than 2% PVA.

www.superbheater.com