GB2603003A - Method of etching a plastic component - Google Patents

Abstract

A method of etching a plastic component is described. The method comprises: providing a plastic component with a plastic outer surface; providing an etching solution comprising Mn(III) ions and a superacid; and contacting the plastic outer surface with the etching solution. The etching solution may comprise Mn(III) ions at a concentration of 10-100mM and where the super acid has a Hammett acidity function H0 of less than -12. The superacid can be perchloric acid, magic acid, trifluoroethane sulfonic acid, fluorosulfuric acid hydrogen fluoride, fluoroboric acid or fluoroantimonic acid. The etching solution can be aqueous. The plastic component may be or a car or automobile

Description

Method of etchina a plastic component The invention relates to a method of etching a plastic component, a method of plating a plastic component and an etching solution for etching a plastic 5 component.

In order to cover plastic or nonconductive substrates with a metal coating (metallize), it is common to use very concentrated solutions of chromic acid as a pretreatment (etch) for the plastic substrate. Normally this is the first step in the metallization process. The etch treatment results in a micro-roughening of the surface that makes the surface more susceptible to the application of a catalyst for the subsequent metallization steps, a process well known to those skilled in the art. The micro-roughening results from oxidation and scission of the double bond on polybutadiene molecules in the substrate, leading to cleavage of the polymer and dissolution and subsequent micro-cavities in the substrate surface.

The use of chromic acid is increasingly regulated due to its hazardous (carcinogenic) nature and a number of alternative treatments have been proposed. However, none of them are capable of direct substitution of the chromic acid etch bath for various reasons, for example the etching rate is too slow, the adhesion between the substrate and the metal deposit is not strong enough, etc. Many proposed alternatives are based on manganese(VII)-containing baths, such as those of US2005/199587A1, US8394289, EP2639333 and US9023228. Manganese (VII) in the form of permanganate, is a strong oxidant that is capable of etching some plastics. Permanganate ions are stable in neutral or alkaline solutions but the etching ability is not strong enough under these conditions to effectively treat the most common plastics used such as ABS and ABS alloys.

Acidic permanganate solutions can etch these plastics, but acidic permanganate baths are unstable; in a relatively short period of time large amounts of manganese dioxide sludge are formed and the etch bath must be discarded.

A recent development is based on the use of manganese (Ill) ions in strong acid (see US9534306, 1JS8603352), where the manganese (Ill) ions can be generated by electrolysis. The advantages over acidic permanganate etch baths are improved bath stability and the ability to re-oxidise manganese (II) back to manganese (Ill) electrolytically and therefore avoid the need to add further chemicals into the bath. These solutions are capable of etching plateable ABS and ABS alloys (e.g. ABS/PC) but the etching rate is slower than chromium (VI) baths. The etching rate can be increased by the use of a 'pre-etch' or sweller step, commonly an aqueous solution of organic solvents. The organic compounds penetrate into the plastic surface and make the substrate more susceptible to etching, leading to deeper etch cavities, improved acceptance of the catalyst and improved adhesion of the metal deposit. However, excessive use of such solvents baths can lead to delamination of the metal deposit when the parts are subjected to thermal stress. This then leads to a high failure rate in the demanding thermal tests required by automotive manufacturers, especially with ABS/PC alloys containing a high percentage of polycarbonate (e.g. 45% or more). The need for a pre-etching step also increases the process cost and complexity.

To obtain even etching of the substrate, chromic acid etching baths typically incorporate a wetting agent to reduce the surface tension of the etch bath. This ensures that the etch solution effectively covers and contacts the plastic surface immediately on the immersion of the substrate into the etch bath. Etching baths that replace chromic acid baths also contain similar wetting agents. Due to the strong oxidising nature of the etching solutions, the only wetting agents that have proven stability in these conditions are perfluoroalkanesulphonates. Historically the most popular of these was perfluorooctanesulfonic acid (PFOS) or its salts, which in the last decade or so has been eliminated due to environmental reasons. The most effective replacements are partially fluorinated analogues, for example tridecafluorooctanesulfonic acid being the most common. This compound contains 8 carbon atoms, of which 6 are fully fluorinated and 2 are hydrogenated. Compounds such as these and similar analogues are commonly referred to as PFAS -PolyFluoro Alkyl Substances -and these are now coming under increased pressure to be eliminated too.

The present invention seeks to tackle at least some of the problems associated with the prior art or at least to provide a commercially acceptable alternative solution thereto. In particular, the present invention seeks to increase the etching rate of acidic manganese (III) baths and eliminate the requirement for pre-etch treatments.

In a first aspect, the present invention provides a method of etching a plastic component, the method comprising: providing a plastic component comprising a plastic outer surface; providing an etching solution comprising Mn(III) ions and a superacid; and contacting the plastic outer surface with the etching solution.

Each aspect or embodiment as defined herein may be combined with any other aspect(s) or embodiment(s) unless clearly indicated to the contrary. In particular, any features indicated as being preferred or advantageous may be combined with any other feature indicated as being preferred or advantageous.

It has surprisingly been found that incorporating a superacid into the Mn(III) etching solution may significantly increase the etching ability of the etching solution. Furthermore, in a subsequent metal plating step, good adhesion of metal may be obtained on the etched substrates without the use of a sweller or pre-etching step. Such advantages may be obtained without the incorporation of permanganate ions or chromic acid in the etching solution. Accordingly, in comparison to conventional etching methods, the method of the present invention is more environmentally friendly and less harmful to human health.

The plastic component is typically a plastic component that is to be etched prior to being metal plated or metallised. Such etching may enable particularly favourable metal plating or metallisation, and the resulting plated plastic component may exhibit a high adhesion between the plated metal and the plastic.

The term "plastic" used herein may encompass a synthetic or semi-synthetic material containing one or more polymers as a main ingredient (e.g. typically greater than 70 wt. % polymer, more typically greater than 85 wt. % polymer, even more typically greater than 95 wt. % polymer). The plastic may contain one or more additives such as, for example, stabilisers, fillers, plasticisers and colorants. The term "plastic component" used herein may encompass a component that contains plastic. The plastic component typically consists of plastic. Alternatively, the plastic component may comprise plastic together with other materials. For example, the plastic component could be made up of a core of a non-plastic material and a plastic outer coating. The plastic component comprises a plastic outer surface. Typically, the entire outer surface of the plastic component is plastic. Alternatively, only some of the entire outer surface of the plastic material is plastic.

The term "superacid" as used herein encompasses an acid having an acidity stronger than that of 100% sulfuric acid. It has been defined more accurately by the Hammett acidity function (Ho), which assigns 100% (18.4M) sulfuric acid a value of -11.9. A more negative value indicates a stronger acidity. In other words, the term "superacid" used herein encompasses an acid having a Hammett acidity function (Ho) of less than, i.e. more negative than, -11.9. The superacid is preferably water-soluble, non-toxic and stable in the etch solution.

Contacting the plastic outer surface with the etching solution typically comprises immersing the plastic component in the etching solution, more typically completely immersing the plastic component in the etching solution.

The etching solution comprises Mn(III) ions. At least some of the Mn(III) ions may be in the form of a complex, typically a metastable complex. Substantially all of the Mn(III) ions may be in the form of a complex, typically a metastable complex. The complex may be, for example a sulfate complex.

The etching solution preferably comprises Mn(III) ions at a concentration of from 10 to 100 mM, more preferably from 50 to 80 mM, even more preferably from 65 to 70 mM. Lower concentrations of Mn(III) may result in only limited etching ability. Higher concentrations of Mn(III) may result in the etching solution becoming unstable and/or "over etching" of the plastic component.

The superacid preferably has a Hammett acidity function Ho of less than -12, preferably less than -13, more preferably less than -14. More negative values may provide a higher etching activity.

The superacid preferably comprises one or more of: perchloric acid (HCI04, Ho = -13), trifluoromethanesulfonic acid ("triflic acid", HOSO2CF3, Ho = -14.9), hydrogen fluoride (HF, Ho = -15.1), fluorosulfuric acid (FSO3H, Ho = -15.1), fluoroboric acid (HF:BF3, Ho = -16.6), magic acid (HSO3F:SbFs, Ho = -19.2), and fluoroantimonic acid (HF:SbF5, Ho between -21 and -23). Such superacids may provide particularly high etching activity. In addition, preferred superacids are water-soluble, non-toxic and stable in the etch solution. Preferred superacids do not attack apparatus typically used to carry out etching and/or metal plating.

The superacid more preferably comprises trifluoromethanesulfonic acid ("triflic acid"). Trifluoromethanesulfonic acid exhbits a particularly high etching activity. In addition, trifluoromethanesulfonic acid may advantageously lower the surface tension of the etch bath. This means that the etch bath may be used without having to add a wetting agent, such as a PFAS wetting agent. Wetting agents are often required in prior art etch baths in order to provide a more even etching pattern, especially on complicated shaped parts with small recesses and/or sharp edges. The omission of a wetting agent may reduce the cost, environmental impact and complexity of the etch bath.

The etching solution preferably comprises from 10 to 200 g/L superacid, more preferably from 20 to 150 g/L superacid, even more preferably from 50 to 120 g/L superacid, still even more preferably from 85 to 110 g/L superacid based on the total volume of the etching solution. For example, when the superacid comprises trifluoromethanesulfonic acid, the etching solution preferably comprises from 0.07 to 1.3 M, more preferably from 0.13 to 0.8 M, even more preferably from 0.56 to 0.73 M trifluoromethanesulfonic acid. Lower concentrations of superacid may provide only a limited etching activity. Higher concentrations may lead to "over etching" and damage to the plastic component. In addition, at higher concentrations the solubility of the Mn(III) ions may be reduced.

The plastic outer surface is preferably contacted with the etching solution at a temperature of from 50 to 90 °C, more preferably from 60 to 80 °C, even more preferably from 65 to 75 °C. Lower temperatures may provide only limited etching activity and/or require longer etching times. Higher temperatures may lead to "over etching" and/or loss of solvent from the etching solution. Higher temperatures may also result in damage to the plastic component.

The plastic outer surface is preferably contacted with the etching solution for from 1 to 60 minutes, more preferably from 5 to 40 minutes, even more preferably from to 30 minutes. Shorter times may result in only limited etching and/or require higher temperatures. Longer times may result in "over etching" and/or loss of an unfavourable amount of solvent from the etching solution.

The plastic outer surface (and typically the entire plastic component) preferably comprises acrylonitrile butadiene styrene (ABS) and/or acrylonitrile butadiene styrene polycarbonate (ABS/PC). ABS has the chemical formula (C8H8)x-(C4H6)y(C3H3N)z) and is a common thermoplastic polymer known in the art. ABS/PC comprises a blend of acrylonitrile butadiene styrene and polycarbonate. Such materials are commonly used as substrates in a metal plating process, and are required to undergo etching prior to plating. Etching of such materials may render the materials particularly suitable for metal plating.

The etching solution preferably further comprises one or more acids in addition to the superacid, preferably wherein the one or more acids is selected from methyl sulfonic acid, sulfuric acid and phosphoric acid, more preferably wherein the one or more acids are sulphuric acid and one or both of methyl sulfonic acid and phosphoric acid. The presence of such acids may increase the solubility of the Mn(III), for example by the formation of Mn(III) complexes (e.g. Mn(III) sulfate complexes) thereby increasing the stability of the etching solution. When the Mn(III) is generated in an electrochemical cell by the oxidation of Mn(II), the presence of such acids may serve to increase the solubility of the Mn(II).

The etching solution may further comprise a wetting agent. An example of a commercial wetting agent suitable for use in the present invention is Capstone@ Fluorosurfactant FS-10 available from DuPontTM. The etching solution is preferably substantially free of wetting agent (e.g. a PEA wetting agent), more preferably completely free of wetting agent. The absence of wetting agents, in particular PFAS wetting agents, results in a simpler and more environmentally friendly method.

The etching solution is preferably substantially free of permanganate ions, more preferably completely free of permanganate ions. This may reduce the formation of a manganese dioxide sludge, which may form due to the low pH of the etching solution.

The etching solution is preferably an aqueous solution. Water is a particularly effective solvent, is non-hazardous, low-cost, environmentally friendly and widely available.

The etching solution may comprise the recited elements. Alternatively, the etching solutions may consist of the recited elements. Alternatively, the etching solution may consist essentially of the recited elements, meaning that specific further components can be present, namely those not materially affecting the essential characteristics of the etching solution.

The component may typically comprise any plastic component that is required to be electroplated. Examples include an automotive support (e.g. automotive grilles, headlamp surrounds, door handles and decorative trim), a shower fitting support, a bathroom fitting support, household fittings and furniture fittings and electronics components (e.g. cameras, computers, telephones).

The method preferably further comprises recovering the plastic component from the etching solution, more preferably wherein the recovering comprises rinsing the plastic component, for example in water and/or an acid solution.

In a preferred embodiment, providing an etching solution comprising Mn(III) ions and a superacid comprises: providing an electrochemical cell comprising an anode, a cathode and an electrolyte in contact with the anode and the cathode, the electrolyte comprising Mn(II) ions and a superacid; and applying a current between the anode and the cathode.

On applying the current, the Mn(II) ions oxidise to Mn(III) ions. The Mn(III) ions are typically formed in the form of a metastable complex, as discussed above. Suitable sources of Mn(II) ions include, for example, manganese sulfate, manganese carbonate and manganese hydroxide. The Mn(II) is typically present in the electrolyte in a concentration of from 0.01 M up to saturation. So as to maintain the stability of the electrolyte, it is preferable that no more than 50%, and more preferable that no more than 25%, of Mn(II) be oxidised. The current is preferably applied with a current density of from 0.1 to 0.4 A/dm2 based on nominal surface area. Higher current densities may mean that the potential of the anode is sufficiently high to liberate oxygen, so conversion efficiency of Mn(II) to Mn(III) falls. In addition, manganese dioxide may form at the anode surface rather than Mn(III) ions. Suitable materials for the anode are known in the art and include, for example, vitreous carbon, reticulated vitreous carbon, woven carbon fibres, lead, lead alloy, platinum, platinized niobium, iridium and/or tantalum oxide coated niobium, boron doped diamond and combinations thereof. Suitable materials for the cathode are known in the art and include, for example, platinum, platinized niobium, lead, lead alloy and some highly corrosion resistant grades of stainless steel.

In a further aspect, the present invention provides a method of etching a component having an outer surface comprising a plastics material, the method 10 comprising: providing a component having an outer surface comprising a plastics material; providing an etching solution comprising Mn(III) ions and a superacid; and contacting the outer surface with the etching solution.

For the avoidance of doubt, the advantages and preferable features of the first aspect apply equally to this aspect. The term" plastics material" as used herein may encompass a synthetic or semi-synthetic material containing one or more polymers as a main ingredient (e.g. typically greater than 70 wt. % polymer, more typically greater than 85 wt. Yo polymer, even more typically greater than 95 wt. °A, polymer). The plastic material may contain one or more additives such as, for example, stabilisers, fillers, plasticisers and colorants.

In a further aspect, the present invention provides a plastic component etched according to the method described herein.

For the avoidance of doubt, the advantages and preferable features of the first aspect apply equally to this aspect.

In a further aspect, the present invention provides a method of plating a plastic component, the method comprising: providing a plastic component comprising a plastic outer surface; etching the plastic component according to the method described herein to provide an etched outer surface; contacting the etched outer surface with an activator solution to form an activated outer surface; and contacting the activated outer surface with a metal plating solution to form a plated component.

For the avoidance of doubt, the advantages and preferable features of the first aspect apply equally to this aspect.

Suitable activator solutions are known in the art. Contacting the etched outer surface with the activator solution preferably comprises at least partially immersing the etched component in the activator solution, more preferably completely immersing the etched component in the activator solution. The contacting is typically carried out at ambient temperature, although elevated temperatures may be used. The contacting is preferably carried out for at least 30 seconds, more preferably at least a minute, even more preferably from 1 to 20 minutes, still even more preferably from 1 to 10 minutes.

Prior to contacting the etched outer surface with the activator solution, the etched outer surface may be contacted with an acid, for example hydrochloric acid. This is because typical activators comprise colloids that sometimes exhibit limited stability in water. If the wet plastic surface is immersed directly into the colloid solution, the colloid at the plastic surface may become unstable.

Depending on the metallisation technology to be employed, after contacting the etched outer surface with the activator solution, the activator may be contacted with an accelerator solution, e.g. to remove tin originating from some activator baths. The presence of tin on the surface may inhibit metallisation.

The metal plating solution preferably comprises a nickel plating solution or a copper plating solution. The nickel plating solution may be an electroless nickel plating solution, and the copper plating solution may be an electroless copper plating solution. Suitable electroless nickel and electroless copper solutions are known in the art. Typical electroless solutions comprise ions of nickel or copper together with a reducing agent such as, for example, a hypophosphite reducing agent. Contacting the activated outer surface with an electroless nickel solution or an electroless copper solution preferably comprises at least partially immersing the activated component in the electroless nickel solution or the electroless copper solution, more preferably completely immersing the activated component in the electroless nickel solution or the electroless copper solution. The plated component may be subjected to one or more further plating steps, for example to form a final outer layer of chrome, copper, nickel, brass, bronze or a precious metal, e.g. silver or gold.

The component is typically rinsed, for example in water and/or acid solution, after being contacted with the etching solution and/or activator solution and/or the electroless nickel solution and/or the electroless copper solution and prior to the next step. After being contacted with the etching solutions and/or activator solution and/or the electroless nickel solution and/or the electroless copper solution, the component may be recovered from the respective solution.

In a preferred embodiment: the plated component comprises a metal layer adhered to the plastic component; the plastic component comprises acrylonitrile/butadiene/styrene (ABS) or acrylonitrile/butadiene/styrene/polycarbonate (ABS/PC); and when the plastic component comprises acrylonitrile/butadiene/styrene (ABS), the adhesion of the metal layer to the plastic component is at least 7 N/cm according to ASTM B533-85 (2019), and when the plastic component acrylonitrile/butadiene/styrene/polycarbonate (ABS/PC), the adhesion of the metal layer to the plastic component is at least 3.5 N/cm according to ASTM B533-85 (2019).

Such levels of adhesion may be sufficient to meet requirements for automobile components in various countries.

In a further aspect, the present invention provides a plastic component plated according to the method described herein.

For the avoidance of doubt, the advantages and preferably features of the first aspect apply equally to this aspect.

In a further aspect, the present invention provides an etching solution for etching a plastic component, the etching solution comprising Mn(III) ions and a superacid.

For the avoidance of doubt, the advantages and preferable features of the first aspect apply equally to this aspect.

The invention will now be described in relation to the following non-limiting drawings in which: Figure 1 shows electron micrographs of ABS surfaces contacted with various acids and an ABS surface not contacted with acid.

Figure 2 shows plots of surface roughness against specific gravity for plastics etched with etching solutions with or without triflic acid.

Figures 3-7 show SEM micrographs of plastics etched according to Example 3.

The invention will now be described in relation to the following non-limiting examples.

Example 1

The effects of pure acids (sulfuric acid, fluorosulfuric acid and triflic acid) on an ABS surface were investigated. Undiluted acid was placed on the plastic surface and allowed to stand for 10 minutes before the acid was washed away and the surface evaluated under an electron microscope. The electron micrographs are shown in Figure 1 (5000x; from top to bottom: no acid, sulphuric acid, fluorosulfuric acid and triflic acid). It can be seen that the superacids fluorosulfuric acid and triflic acid are more aggressive than the non-superacid sulphuric acid, with triflic acid being the most aggressive.

Example 2

The effect of adding triflic acid into a manganese (Ill) etching bath was evaluated by measurement of the surface roughness of a plastic substrate. 40 ml/L (68 g/L) of triflic acid was added to an etch bath prepared according to U59534306. A control comparison was also carried out in which 40 ml/L of sulphuric acid was added. The experiment was repeated with varying etch bath density on both ABS and ABS/PC substrates and the surface roughness of etched plastic was measured after 10 minutes immersion at 70°C. The roughness measurement was carried out with a 3D-Laser microscope. The results are shown in Figure 2, and show a clear trend of rougher surface profile with the triflic acid included in the etching bath.

Example 3

Etching baths based on acidic manganese (Ill) were prepared as per table 1 below (all units in g/L): Bath Standard Bath 1 Bath 2 Bath 3 Bath 4 TFMSA 0 154 20 77 50 (99%) MSA (70%) 216 0 216 108 216 MnSO4.H20 20.5 20.5 20.5 20.5 13.7 H2SO4 1049 1049 1049 1049 920 (96%) l-13PO4 115 115 115 115 115 (85%) Capstone FS-10 0.5 0.5 0.5 0.5 0.5 DI water To 1L volume To 1L volume To 1L volume To 1L volume To 1 L volume Table 1: bath contents.

All baths were electrolysed to produce a manganese (Ill) ion concentration of 65 -70 mM. ABS plastic was etched for 10 minutes at 70°C and ABS/PC plastic was etched for 20 minutes at 72°C before being rinsed and dried. The surface was then examined using SEM. The SEM micrographs are shown in Figure 3 (standard -no triflic acid), Figure 4 (Bath 1), Figure 5 (Bath 2), Figure 6 (Bath 3) and Figure 7 (Bath 4), with ABS at the top and ABS/PC at the bottom. Baths with a higher concentration of triflic acid show a deeper etching. Bath 1 is 'over-etched', a phenomenon known to those skilled in the art.

Example 4

Etching baths based on acidic manganese (Ill) were prepared as per table 2 below (all units in g/L) and plastic panels were etched and metallized. The adhesion was evaluated according to ASTM B533 (adhesion units are N/cm).

Bath Standard TFMSA (98%) 0 34 85 102 MSA (70%) 216 216 216 216 216 216 MnSO4.H20 20.5 20.5 20.5 20.5 20.5 20.5 H2SO4 (96°/0) 1049 1049 1049 1049 1049 1049 H3PO4(85°/o) 115 115 115 115 115 115 Capstone FS-10 0.5 0.5 0 DI water To 1L volume Results Etching time ABS (min) 10 15 10 Etching time ABS/PC (min) 15 20 15 Etching temperature ABS (°C) 70 72 Etching temperature ABS/PC (°C) 70 72 Adhesion ABS 1.47 3.13 6.91 8.51 10.51 10.71 Adhesion ABS/PC 1.94 3.02 3.91 4.35 5.20 5.73 Table 2: bath contents, etching conditions and adhesion values.

The results above demonstrate that the addition of triflic acid improves the depth 5 of etching on ABS and ABS/PC substrates, and that an increased concentration can be correlated with a trend of increased adhesion.

The foregoing detailed description has been provided by way of explanation and illustration, and is not intended to limit the scope of the appended claims. Many variations in the presently preferred embodiments illustrated herein will be apparent to one of ordinary skill in the art and remain within the scope of the appended claims and their equivalents.

Claims (20)

1. Claims: 1. A method of etching a plastic component, the method comprising: providing a plastic component comprising a plastic outer surface; providing an etching solution comprising Mn(III) ions and a superacid; and contacting the plastic outer surface with the etching solution.
2. 2. The method of claim 1, wherein the etching solution comprises Mn(III) ions at a concentration of from 10 to 100 mM, preferably from 50 to 80 mM, more preferably from 65 to 70 mM.
3. 3. The method of claim 1 or claim 2, wherein the superacid has a Hammett acidity function Ho of less than -12, preferably less than -13, more preferably less than -14.
4. 4. The method of any preceding claim, wherein the superacid comprises one or more of: perchloric acid, trifluoromethanesulfonic acid, hydrogen fluoride, fluorosulfuric acid, fluoroboric acid, magic acid and fluoroantimonic acid, preferably trifluoromethanesulfonic acid.
5. 5. The method of any preceding claim, wherein the etching solution comprises from 10 to 200 g/L superacid, preferably from 20 to 150 g/L superacid, more preferably from 50 to 120 g/L superacid, even more preferably from 85 to 110 g/L superacid based on the total volume of the etching solution.
6. 6. The method of any preceding claim, wherein the plastic outer surface is contacted with the etching solution at a temperature of from 50 to 90 °C, preferably from 60 to 80 °C, more preferably from 65 to 75 °C.
7. 7. The method of any preceding claim, wherein the plastic outer surface is contacted with the etching solution for from 1 to 60 minutes, preferably from 5 to 40 minutes, more preferably from 10 to 30 minutes.
8. 8. The method of any preceding claim, wherein the plastic outer surface comprises acrylonitrile/butadiene/styrene (ABS).
9. 9. The method of any preceding claim, wherein the plastic outer surface comprises acrylonitrile/butadiene/styrene/polycarbonate (ABS/PC).
10. 10. The method of any preceding claim, wherein the etching solution further comprises one or more acids in addition to the superacid, preferably wherein the one or more acids is selected from methyl sulfonic acid, sulfuric acid and phosphoric acid.
11. 11. The method of any preceding claim, wherein the etching solution is substantially free of wetting agent.
12. 12. The method of any preceding claim, wherein the etching solution is substantially free of permanganate ions.
13. 13. The method of any preceding claim, wherein the etching solution is an aqueous solution.
14. 14. The method of any preceding claim, wherein the plastic component is a component for an automobile.
15. 15. The method of any preceding claim, wherein the method further comprises recovering the plastic component from the etching solution, preferably wherein the recovering comprises rinsing the plastic component.
16. 16. The method of any preceding claim, wherein providing an etching solution comprising Mn(III) ions and a superacid comprises: providing an electrochemical cell comprising an anode, a cathode and an electrolyte in contact with the anode and the cathode, the electrolyte comprising Mn(II) ions and a superacid; and applying a current between the anode and the cathode.
17. 17. A method of plating a plastic component, the method comprising: providing a plastic component comprising a plastic outer surface; etching the plastic component according to the method of any of claims 1 to 16 to provide an etched outer surface; contacting the etched outer surface with an activator solution to form an activated outer surface; and contacting the activated outer surface with a metal plating solution to form a plated component.
18. 18. The method of claim 17, wherein the metal plating solution comprises a nickel plating solution or a copper plating solution, preferably an electroless nickel plating solution or an electroless copper plating solution.
19. 19. The method of claim 17 or claim 18, wherein: the plated component comprises a metal layer adhered to the plastic component; the plastic component comprises acrylonitrile/butadiene/styrene (ABS) or acrylonitrile/butadiene/styrene/polycarbonate (ABS/PC); and when the plastic component comprises acrylonitrile/butadiene/styrene (ABS), the adhesion of the metal layer to the plastic component is at least 7 N/cm according to ASTM B533-85 (2019), and when the plastic component acrylonitrile/butadiene/styrene/polycarbonate (ABS/PC), the adhesion of the metal layer to the plastic component is at least 3.5 N/cm according to ASTM B533-85 (2019).
20. 20. An etching solution for etching a plastic component, the etching solution comprising Mn(III) ions and a superacid.