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EP1438448A1 - Procede electrolytique et compositions de decapage de depot autocatalytique de nickel - Google Patents

Procede electrolytique et compositions de decapage de depot autocatalytique de nickel

Info

Publication number
EP1438448A1
EP1438448A1 EP01981784A EP01981784A EP1438448A1 EP 1438448 A1 EP1438448 A1 EP 1438448A1 EP 01981784 A EP01981784 A EP 01981784A EP 01981784 A EP01981784 A EP 01981784A EP 1438448 A1 EP1438448 A1 EP 1438448A1
Authority
EP
European Patent Office
Prior art keywords
oxoacids
composition
nickel
hydrogen peroxide
acid
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP01981784A
Other languages
German (de)
English (en)
Inventor
Barry W. Coffey
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Atotech Deutschland GmbH and Co KG
Original Assignee
Atotech Deutschland GmbH and Co KG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Atotech Deutschland GmbH and Co KG filed Critical Atotech Deutschland GmbH and Co KG
Publication of EP1438448A1 publication Critical patent/EP1438448A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
    • C25F5/00—Electrolytic stripping of metallic layers or coatings
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D1/00—Electroforming
    • C25D1/20—Separation of the formed objects from the electrodes with no destruction of said electrodes
    • C25D1/22—Separating compounds

Definitions

  • the present invention relates to an electrical stripping process and compositions for stripping electroless nickel from a substrate.
  • An electrical stripping process can be described as the reverse of electroplating. While electroplating applies a coating of metal to a substrate, an electrical stripper removes a coating from the substrate. The coating is dissolved during electrolysis by combining with negative chemical ions in a bath, which are attracted to its surface by its positive potential. While the object of a stripper is to remove a coating without damage to the underlying substrate, most anodic reactions cannot differentiate between the coating and the substrate resulting in etching of that substrate.
  • Electroless nickel is a very chemical resistant coating and is difficult to attack.
  • An illustration of its chemical resistant is the "nitric acid drop test”. A drop of concentrated nitric acid is applied to the electroless nickel coating's surface. If any etching occurs within a set time period, the test fails.
  • the discovery of relatively mild chemical formulations and procedures that will rapidly strip these very chemical resistant coatings is of great economic value. This is especially true when the stripping process can be made environmentally friendly and safe to use in the recovery of defectively plated parts.
  • U. S. Patent 4,356,069 (Cunningham) describes an electrical nickel stripper composed of concentrated sulfuric acid, chromic acid, and hydrogen peroxide.
  • This formulation claimed to strip chromium as well as nickel from ferrous substrates. While the patent does not claim that the formulation will strip electroless nickel deposits, it suffers from the disadvantages of high disposal costs of its large hazardous chromium and sulfuric acid content, and the added step of having to remove an oxide layer from the substrate before replating can be attempted.
  • U. S. Patent 4,664,763 discloses an aqueous stripping solution comprising chromic acid utilizing defectively plated parts as either or both the anode and cathode of an electrolytic stripping cell and applying an alternating current across the electrodes to strip the nickel coatings. Electrolytic and electrolysis nickel coatings are said to be stripped by this method.
  • This stripping method cites several optional etch inhibitors, such as potassium iodide, to help prevent etching of the substrate. This method suffers from the possibility of etching and the high disposal cost of the high chromic acid content.
  • nitrates normally ammonium or sodium nitrate
  • These processes use reverse direct current to remove electroplated nickel and some low phosphorous electroless nickel deposits from iron and steel.
  • the stripping bath undergoes rapid pH changes that produce heavy sludging problems. Sporadic passivity of large areas of unstripped nickel occur as the exposed base metal becomes passive under the influence of the electric current causing an incompletely stripped part. The problem is more pronounced when trying to strip electroless nickel deposits above about seven percent phosphorous.
  • Nickel stripping baths that utilize water soluble nitrobenzene compounds, either ammonia and ammonium salts or ethylene diamine and/or its homologs, have gained wide acceptance. These baths work well on deposits of electrolytic nickel and some low phosphorous electroless nickels have achieved stripping rates of about 0.001 inch/hour, however, the high phosphorous content electroless deposits slowed the removal to, on average, less than 0.0003 inch an hour. Proper disposal of these types of stripping baths is very expensive because of their toxicity and high chelating power. These baths operate at about 160 - 190 ° Falirenheit to strip electroless nickel coatings and are very vulnerable to damage by heat through loss of volatile chemicals components as well as thermal chemical decomposition.
  • U. S Patent 4,554,049 discloses an immersion nickel stripper which uses sulfamic acid, hydrogen peroxide, nitrates, and chlorides.
  • U. S. Patent 4,720,332 (Coffey) describes a nickel stripping bath that utilizes soluble nitrobenzene compounds, Zwitterions (as chelating agents), sulfide producing compounds, carbonates, and the use of reverse current for the fast removal of electroless nickel deposits. While this method strips electroless nickel fast (up to 0.002 inch/hour) and works well, it sometimes microscopically etches in high current density areas dulling highly polished surfaces.
  • the electrolytic stripping baths of the present invention are made from oxoacids, and/or oxoacid salts, and hydrogen peroxide. It has been discovered that electroless nickel deposits can be dissolved at the anode of electrolytic baths containing oxoacids, and/or oxoacid salts, and hydrogen peroxide.
  • the substrates of iron, cast iron, steel alloy, stainless steel, and titanium are protected from attack during electrolysis if the hydrogen peroxide/acid mole ratio is maintained above a minimum preferred mole ratio of about 3.75 for strong oxoacids with one ionizable hydrogen and about 7.5 hydrogen peroxide/oxoacid mole ratio for strong oxoacids with two or more ionizable hydrogens.
  • Peroxide/oxoacid ratios as low as 1.5 may be used when combining weak oxoacids with weak oxoacid salts to construct a stripping bath.
  • sulfuric and sulfamic acids and/or their salts may be selected from the strong oxoacids while any of the hydrogen peroxide compatible weak oxoacids and/or salts may be used. Only combinations of weak oxoacids and/or oxoacid salts should be used when stripping from the substrates of electroplated nickel, cast nickel, kovar (iron, nickel, cobalt alloy), and sulfamate nickel.
  • an acid is considered strong if it has a dissociation constant (Ki) greater than about 2 X 10 "1 .
  • strong oxoacids include sulfuric, nitric, sulfamic, alkyl sulfonic, aryl sulfonic, and monoalkyl esters of sulfuric acid.
  • weak oxoacids include phosphoric, pyrophosphoric, alkyl phosphoric, glucophosphonic, oxalic, formic, propanoic, bis methanol propanoic, acetic, butanoic, benzoic, phthalic, citric, tartaric, malic, malonic, maleic, butyric, succinic, glycolic, glutaric, gluconic, adipic, boric, ethylenediaminetetraacetic and homologs, nitrilotriacetic, amino acetic, and polyvinyl sulfonic acid.
  • the concentration of hydrogen peroxide for the application of this invention can range from about one percent to about 99 percent, but a concentration of about eight percent is preferred. While maintaining the disclosed minimum peroxide/oxoacid mole ratios the oxoacid and/or oxoacid salts may vary from 0.01 mole/liter to saturation.
  • the pH range for implementation of the invention is about 0-8, while the preferred pH range is about 1-7, and the most preferred range is about 1.5-4.5.
  • oxygen free halogen acids hydrofluoric and hydrochloric are excluded from the invention because there seems to be no hydrogen peroxide/acid ratio that will prevent attack on iron or steel substrates when these acids and/or their salts are used in the stripping bath in amounts above about 0J mole/liter.
  • Iodic, bromic, and chromic acids and/or salts are excluded because of their incomparability with hydrogen peroxide either upon mixing with peroxide or during the stripping process.
  • electroless nickel deposits can be electrolytically stripped from substrates of iron, cast iron, steel alloy, stainless steel, aluminum, and titanium utilizing stripping baths made from selected oxoacids and/or oxoacid salts and hydrogen peroxide.
  • electrolytically deposited nickel, cast nickel, kovar, and high nickel alloy substrates can be stripped of electroless nickel deposits without significant substrate attack provided the stripping bath is made from weak oxoacids and or oxoacid salts.
  • Electroless nickel can be stripped from aluminum substrates without significant attack only if the strong oxoacids and /or strong oxoacids salts are selected from sulfuric acid and its salts and/or sulfamic acid and its salts. Any of the hydrogen peroxide compatible weak oxoacids and/or oxoacid salts may be used to strip electroless nickel from aluminum.
  • the base metals are protected from attack during electrolysis if the hydrogen peroxide/oxoacid mole ratio is maintained above a minimum of about 3.75 for strong oxoacids with one ionizable hydrogen and about 7.5 hydrogen peroxide/oxoacid mole ratio for strong oxoacids with two or more ionizable hydrogens.
  • Peroxide/oxoacid ratios as low as 1.5 maybe used when combining weak oxoacids and/or weak oxoacid salts to construct a stripping bath.
  • oxygen free halogen acids hydrofluoric and hydrochloric are excluded from this invention because there is no apparent concentration of hydrogen peroxide that will prevent attack of iron, steel alloy, and aluminum substrates when these acids are present in the stripping bath at a concentration greater than about 0J mole/liter.
  • Very small amounts of halogen ions do not seem to attack the substrate if accompanied in solution by relatively large amounts of oxoacid ions.
  • the amount of chloride ion resulting from chlorination of drinking water does not seem to affect the substrate, however, if the concentration of chloride ion rises above about 0J mole per liter, some attack of the substrate may result.
  • the concentration of oxoacid and/or oxoacid salts may vary over wide limits as long as the minimum peroxide/acid mole ratios are maintained.
  • the acid and/or salts may vary from 0.01 mole/liter to saturation.
  • the stripping bath since the current that flows through the bath determines the amount of nickel stripped during a time period, it is preferred that the stripping bath have a low electrical resistance. Therefore, selection of the amount and type of oxoacids and/or oxoacid salts that increase the conductivity of the solution is of great importance for the rapid and economic removal of the electroless nickel coating.
  • the preferred temperature range for operating the stripping baths of this invention is about 60-115 ° F, and the most preferred is about 80-100 ° F.
  • lower or higher temperatures may be used, however, lower conductivity and solubility will be experienced at lower temperatures, and accelerated peroxide decomposition may occur at higher temperatures.
  • the following bath was not chelated which makes waste treatment of spent stripping baths of this formulation simple and low in cost. It contained only about three times the acetic acid content of ordinary vinegar which makes it very safe to use. While the peroxide content was high enough to bleach hair, it is not a high enough concentration to be a serious hazard to workers.
  • a TEFLON® (polytetrafluoroethylene) coated stirring rod was placed in the beaker and was used to slowly stir the solution to prevent stratification of the bath. The current was applied and the voltage drop across the stripping bath was adjusted to four. After a momentary formation of bubbles on the plated part, the nickel began to dissolve into the stripping bath and all bubbling at the anode stopped. The starting current was 0.75 amps. After about thirty minutes, the steel base metal began to be exposed at the 90-degree angles on the bottom of the plated part. Unlike nitrate based electrolytic strippers, the exposed steel substrate did not gas. The electroless nickel coating continued to dissolve, and as it receded, it assumed a parabolic shape as it shrank from all sides of the panel.
  • Example 2 The following examples were constructed as in Example 1 and illustrate the varied oxoacids and/or oxoacid salts that may be used in this invention:
  • Example 2 The following examples were constructed as in Example 1 and illustrate the varied oxoacids and/or oxoacid salts that may be used in this invention:
  • Example 1 This bath had less resistance to the flow of current than Example 1 and the starting current was 1.02 amperes at a starting voltage drop across the bath of four volts. An identical panel to the one used in Example 1 was stripped in about thirty minutes with identical good results.
  • Example 4 This bath was constructed as in Example 1. This bath had very good conductivity. It stripped from the substrates of steel, aluminum, and titanium with no visible attack. 2.35 grams of nickel were introduced into the bath and calculations showed that 97.9 % of the acid had been used to react with nickel. Additional use of this bath caused the pH to rise rapidly from the 4.8 pH that was measured when the nickel content reached 2.35 grams. Continued stripping caused precipitation of nickel hydroxide and rapid decomposition of the hydrogen peroxide as the pH reached about 6-7. No additions of hydrogen peroxide were necessary during the test. Example 4
  • This bath was tested to 60 amps./sq. ft. No attack on steel, aluminum, or titanium base metals was observed.
  • This bath gave good results stripping nickel from steel, aluminum, and cast iron substrates.
  • This bath stripped about 10 times slower at four volts than the bath in Example 1 because of poor bath conductivity. The bath does not attack steel substrate.
  • the bath stripped 4.2 grams nickel which is the stoichiometric equivalent of the citric acid in the bath.
  • the pH of the bath began to rise rapidly and the test was terminated. No attack on steel, aluminum, cast iron, or titanium substrates was noted.
  • This bath stripped electroless nickel deposits at near 100% efficiency. No visible attack on steel substrates was observed. Bright electrolytically deposited nickel was slowly (oxygen liberated at nickel's surface) dissolved in this bath because of the nitrate content. Aluminum substrates were slowly attacked.
  • This bath stripped bright electroplated nickel with less efficiency, i.e., some gassing occurs as the electroplated nickel was dissolved. However, 12 % high phosphorous electroless nickel deposits were stripped at near 100 % efficiency.
  • This formulation is an improvement over prior art because it allows the use of an acid to keep the pH from rising to a point where nickel hydroxide precipitation causes sludging of the bath which is an inherent deficiency of prior art nitrate electrolytic strippers. It also allows the nitrate based formulation to strip high phosphorous electroless nickel and bright electroplated nickel in one stripping bath with no attack on steel or cast iron substrates. Aluminum substrates are attacked.
  • This bath stripped bright electroplated nickel with gassing of oxygen. It stripped electroless nickel very rapidly because of high conductivity. With this bath, aluminum substrates, but not steel or titanium substrates, were attacked.
  • the following example has a volume of one liter. This bath illustrates a very low peroxide/oxoacid concentration of 0.3/0.04 moles.
  • this bath stripped electroless nickel of 12 % phosphorous content with no discemable attack on steel or aluminum test panels.
  • Example 30 A one-inch wide unplated steel test panel was immersed into the solution and was immediately attacked before electrical connection was made to the test panel. This panel was replaced with another steel panel that was plated with 0.001 inch electroless nickel. The panel was connected to the positive lead of the power supply as in Example 1 and voltage was adjusted to four volts. The elecfroless nickel was rapidly dissolved because of the high current density. After the panel was stripped of elecfroless nickel and the part was being removed from the stripping bath, it was explosively attacked by the stripping solution remaining on its surface.
  • Example 30 A one-inch wide unplated steel test panel was immersed into the solution and was immediately attacked before electrical connection was made to the test panel. This panel was replaced with another steel panel that was plated with 0.001 inch electroless nickel. The panel was connected to the positive lead of the power supply as in Example 1 and voltage was adjusted to four volts. The elecfroless nickel was rapidly dissolved because of the high current density. After the panel was stripped of elecfroless nickel and the part was being removed from
  • Example 29 An unplated test panel identical to that of Example 29 was immersed into the stripping solution without electrical contact. The test panel was very slowly attacked by the solution. As in Example 29, the panel was replaced by a plated one and stripped. When the panel was removed, the steel base metal was attacked but was not explosive in its rate of attack. Addition of 15 milliliters of hydrogen peroxide (50%) to the above bath stopped all the etching and produced results identical to those obtained in Example 1.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • ing And Chemical Polishing (AREA)

Abstract

L'invention concerne des solutions de décapage électrolytique, contenant des oxacides et/ou des sels d'oxacides, et du péroxyde d'hydrogène. Lesdites solutions ont été formulées pour éliminer rapidement le dépôt autocatalytique de nickel d'alliages de fer, d'acier, d'aluminium, et de titane, ainsi que d'autres substrats conducteurs sélectionnés. Les formulations permettent d'accroître la résistance à l'attaque du substrat et peuvent être formulées sans chélate, ni chromate, nitrate, ou solution d'acide concentré, ce qui augmente la sécurité du travailleur et réduit les coûts d'élimination de déchets de solutions de décapage utilisées.
EP01981784A 2001-10-23 2001-10-23 Procede electrolytique et compositions de decapage de depot autocatalytique de nickel Withdrawn EP1438448A1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US2001/032607 WO2003035944A1 (fr) 2001-10-23 2001-10-23 Procede electrolytique et compositions de decapage de depot autocatalytique de nickel

Publications (1)

Publication Number Publication Date
EP1438448A1 true EP1438448A1 (fr) 2004-07-21

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP01981784A Withdrawn EP1438448A1 (fr) 2001-10-23 2001-10-23 Procede electrolytique et compositions de decapage de depot autocatalytique de nickel

Country Status (5)

Country Link
EP (1) EP1438448A1 (fr)
JP (1) JP2005506457A (fr)
KR (1) KR100618165B1 (fr)
CA (1) CA2458305A1 (fr)
WO (1) WO2003035944A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111621840A (zh) * 2020-05-26 2020-09-04 大连理工大学 一种钛合金表面铁污染的双极电化学清除方法

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB0505353D0 (en) * 2005-03-16 2005-04-20 Chem Technologies Ltd E Treatment process for concrete
US7569490B2 (en) * 2005-03-15 2009-08-04 Wd Media, Inc. Electrochemical etching
US20060207890A1 (en) * 2005-03-15 2006-09-21 Norbert Staud Electrochemical etching
CN114561557B (zh) * 2022-01-15 2023-06-30 南城广德新材科技有限公司 一种快速溶解镍豆的工艺
JP7500088B2 (ja) 2022-04-11 2024-06-17 奥野製薬工業株式会社 金属剥離剤

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5062941A (en) * 1990-10-22 1991-11-05 Union Carbide Coatings Service Technology Corporation Electrolytic process for stripping a metal coating from a titanium based metal substrate
US6332970B1 (en) * 1999-10-22 2001-12-25 Barry W. Coffey Electrolytic method of and compositions for stripping electroless nickel

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO03035944A1 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111621840A (zh) * 2020-05-26 2020-09-04 大连理工大学 一种钛合金表面铁污染的双极电化学清除方法

Also Published As

Publication number Publication date
JP2005506457A (ja) 2005-03-03
WO2003035944A1 (fr) 2003-05-01
KR20040051600A (ko) 2004-06-18
CA2458305A1 (fr) 2003-05-01
KR100618165B1 (ko) 2006-08-31

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