Electrolytic treatment device for preparing plastic parts to be metallized and a method for etching plastic parts
The present invention refers to an electrolytic treatment device having an anodic compartment comprising a non-chromium (VI) etching solution to be treated and immersed therein an anode. The anodic compartment is separated by a membrane from a cathodic compartment comprising a cathodic solution comprising an inorganic acid, wherein the anode and the cathode are used comprising or consisting of a ternary or higher Pb alloy with Sn and at least one further metal selected from the group consisting of Sb, Ag, Co, Bi and combinations thereof. Moreover, a method for etching plastic parts is provided as well.
1. An electrolytic treatment device having
an anodic compartment comprising a chromium (VI) free etching solution as anolyte and immersed therein an anode,
a cathodic compartment comprising a cathodic solution comprising an inorganic acid as catholyte and immersed therein a cathode,
a membrane separating the anodic from the cathodic compartment;
wherein the anode, and optionally the cathode, consist(s) of a ternary or higher Pb alloy with Sn and at least one further metal selected from the group consisting of Sb, Ag, Co, Bi, and combinations thereof,
wherein the chromium (VI) free etching solution consists of:
47-74 wt % of at least one inorganic acid,
0.01-5 wt % of at least one periodate salt,
0.01-0.5 wt % of at least one manganese salt,
0.01-5 wt % of at least one iodate salt, and
water up to 100%.
2. The device according to claim 1 , wherein the at least one further metal is Sb, Bi or Ag.
3. The device according to claim 1 , wherein the alloy comprises from 85 to 95 wt. % of Pb.
4. The device according to claim 1 , wherein the alloy comprises from 0.5 to 10 wt. % of Sn.
5. The device according to claim 1 , wherein the alloy comprises from 0.05 to 10 wt. % of the third metal.
6. The device according to claim 1 , wherein the etching solution consists of:
47-74 wt % of at least one inorganic acid,
1-4 wt % of at least one periodate salt,
0.01-0.1 wt % of at least one manganese salt,
0.01-2 wt % of at least one iodate salt, and
water up to 100%.
7. The device according to claim 6 , wherein the inorganic acid of the anolyte and/or the catholyte is phosphoric acid or sulfuric acid.
8. The device according to claim 6 , wherein the etching solution consists of:
47-74 wt % of at least one inorganic acid,
2.2-3.8 wt %, of at least one periodate salt,
0.01-0.06 wt %, of at least one manganese salt,
0.01-0.64 wt %, of at least one iodate salt, and
water up to 100%.
9. The device according to claim 6 , wherein the periodate salt comprises sodium metaperiodate.
10. The device according to claim 6 , wherein the iodate salt comprises sodium iodate.
11. Method for etching plastic parts with the following steps:
a) providing the electrolytic treatment device of claim 1 ,
b) immersing a plastic part in the etching solution as anolyte in the anodic compartment chamber, and
c) applying a current from 1 to 8 A/dm 2 for re-oxidizing the iodate to periodate in the anodic compartment.
12. The method of claim 11 , wherein the temperature during step c) is from 50 to 80° C.
13. The method according to claim 11 , wherein the re-oxidation rate to reoxidize the iodate to periodate is from 0.1 to 1 g/Ah.
14. The method according to claim 11 , wherein the dissolution of the anode immersed in the etching solution without any current applied is from 0.1 to 3 g/dm 2 day.
15. The method according to claim 11 , wherein the dissolution of the anode immersed in the etching solution with a current from 0.8 to 1 A/dm 2 current applied continuously is from 0.05 to 0.8 g/dm 2 day.