DE1496896A1 - Metal object with a decorative chrome coating and high corrosion resistance - Google Patents

Description

Metal object with decorative chrome plating and high

Corrosion resistance

The present invention relates to metal objects which have been provided with a decorative coating of chrome are, which has an extraordinary resistance to corrosion O

According to the invention, the metal objects are provided with a base layer Coated from ITickel to a thickness of about 20 to 35 microns. On this base layer there is a chrome layer with a thickness of at least 0.5 microns, which however should not exceed 5 microns, this layer should have at least 10 cracks per cm. laugh a special one Embodiment, the chrome coating consists of "two layers with a total thickness of at least 1 but no more than 5 microns »The lower layer should have a thickness of at least 0.25 micron, the upper chrome layer

BATH ORIGINAL

909830/112 7

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should be at least 0.5 micron thick and at least 10 cracks each have cm

The present invention relates to a new method for the electrodeposition of chromium on metal objects.

Chromium, which is widely used as decorative and protective Coating used is generally electrodeposited in such a thin layer that it is suitable for the protection of the base metal is of no great value. To achieve corrosion resistance in a decorative Chromium plating is generally first deposited on the base metal, copper and nickel, and then the decorative chrome plating applied · The corrosion resistance of such a combination is essentially based on the Properties of the Interlayer However, there is still a need in industry, particularly in the automotive industry, after electrolytically applied chrome coatings with improved corrosion resistance.

An object of the invention is therefore to provide a method for electrolytic To provide deposition of corrosion-resistant chrome coatings »

Another object of the invention is a method for electrolytic Deposition of metal combinations, copper-nickel layers with an electrolytically applied chrome coating are provided with significantly improved corrosion resistance,

BATH ORIGINAL 909838/1127

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Other objects and advantages will become apparent from the following description and drawings _o forth ■

It has been found that, under certain conditions, a chrome layer with high corrosion resistance can be obtained by electrolytic deposition of a double chrome coating. Liters, preferably 200 g to 400 g / liter, CrO, and catalyst ions in a ratio of CrO to the catalyst ions of 110i1 to 175: 1, preferably from 120 * 1 to 150i1. The bath temperature can generally fluctuate between 32 and 60 ° C. and is preferably between about 40 and 57 ^° C. The current density used is the usual one, it varies between 4 and 60 A / dm, and depends mainly on the bath temperature. .- ■■ -.

The baths are through the. Presence of sulfate ions and Ions containing fluoride, such as fluosilicate, fluozirconate, fluoaluminate and fluotitanate, catalyzed · When mixed The baths should contain sulfate and fluoride-containing catalysts between $ 15 and 80, preferably between $ 25 and 60, have fluoride-containing catalyst ions, and the remainder should consist of sulfatiqnen, to calculate the weight ratio from CrO, to catalyst ions, the amount of complex Fluprids,. e.g. fluosilicate, halved and added to the amount of suI-fat available added.

909838/1127

After applying the first layer of chrome, the piece will be transferred from the bath tank directly into the tank in which the second layer is to be applied. If there is a considerable amount of time between these two operations before the piece is brought into the bath for electrodeposition of the second layer, then should it can be cleaned and activated according to standard "procedures. The second layer is made of a sulfate- and fluoride-containing one CrO, -Bad applied, which operated in such a way that cracked precipitate, preferably very heavily cracked precipitate, will be formed.

The fluoride ions can be supplied in the form of complex fluorides, such as fluosilicate, fluozirconate, fluotitanate and fluo <fcaluminate. In the case of a mixed sulfate- and fluoride-containing catalyst, between 15 and 80 $, preferably between 35 and 75 $, fluoride ions should be present in the catalyst and the remainder should be present in the form of sulfate ions. To calculate the weight ratio of CrO. To catalyst ions, half the amount of complex fluoride ions is added to the amount of sulfate ions present. In order to achieve good results, a ratio of CrO, to catalyst ions of 50: 1 to 100 »1, preferably between about 65t 1 and about 90» 1, should be present in the CrO, bath g to 450 g / liter, preferably between 175 to 300 g / liter. The deposition is carried out at temperatures between about 32 to 6O ⁰ C, preferably 43-55 ° C is carried out. It will be at usual

909838/1127, _{Λ |}

BATH ORIGINAL

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Current densities worked. The outer chrome layer should be very cracked, preferably more than 40 cracks per cm. However, satisfactory results were also obtained with double electrolytically applied chrome coatings, in which the outer layer had only 10 cracks per cm.The number of cracks per cm is determined microscopically by examining the surface of a sample at a sufficiently high magnification, Z ₀ B ₀ a hundred times magnification, examined. An arbitrary 1 cm straight line is selected in the field of view and the average number of hoists crossing that line is counted «

When electroplating intricate shapes in a given Bad fluctuates the strength of the achieved edition, which one receives under certain conditions, in certain sections of the piece, depending on the cathode current density at each section. Those areas with low current density show the thinnest deposits. In determining suitable conditions for applying good coatings, one must then seek to achieve an average desired thickness on the essential surfaces of the piece to be clad, and at the same time enough should be deposited on the surfaces with a low current density so that one more adequate corrosion protection is achieved. In general, the stronger the layer, the better the protection against corrosion is β To achieve superior corrosion resistance with this double chrome plating, it is desirable that the first layer have an average thickness of at least 0.158 microns, preferably at least 1 micron.

ORIGINAL BATHROOM 909838/1127

However, satisfactory results were also obtained when the thickness was only 0.25 microns »The outer layer should Have an average thickness of at least 0.5 micron »A thickness of at least 1.0 micron is for these Layer preferable. The total thickness of the double layer is preferably more than. 1.5 microns. A superior corrosion resistance However, if the double layer is more than 3.8 microns thick, no more than about 5-6 microns is achieved. Considerably improved corrosion protection results are achieved with a total thickness of the double layer of already 1 micron obtain.

The chrome plating baths are often referred to as chromic acid baths In these, the chromic acid content of the bath is referred to as CrO-, more precisely referred to as chromic anhydride. That Bath can be made by using CrO., As chromic anhydride or in the form of chromium compounds, the cations of which do not adversely affect the bath properties. to such compounds include the chromates, bichromates and polychromates of potassium, sodium, magnesium and calcium, CrO ^ can also be in the form of chromic acid and / or dichromic acid be added in solution.

The catalyst ions can be added to the bath in the form of Corresponding acid and / or as a salt are incorporated with a cation that does not detrimental to the bathing properties influenced. Such cations are e.g. potassium, sodium, calcium, magnesium, strontium, chromium, etc.

909838/1127

BAD ORiGlNAk

The amount of sulfate ions and fluoride-containing ions added to the bath and maintained in the bath should in their sum result in a ratio which corresponds to the values given above. The desired concentration of catalyst ions can be adjusted by adding soluble salts and the concentration determined by analysis of baths that contain mixed sulfate and fluoride-containing catalyst are catalyzed, are preferably prepared and maintained from Salts with solubility properties such that when added in excess of the solubility to the bath, sufficient amounts go into solution and the desired ratio is established «(Often the solubility is increased by the presence further reduced by "suppressor salts"). Self-regulating and controllable baths can be made from salts such as strontium sulfate and potassium silicofluoride. Baths catalyzed with sulfate ions and fluoride-containing ions, which are operated at temperatures above about 45 °, a first chromium layer is created, which, depending on the regulation of the shows practically no cracks in other response variables. These Baths have excellent hiding power and when used as indicated and a second layer is electrolytic is applied, a glossy double ear pad with good coverage and considerable thickness is obtained deep spots and fine cracks over the larger ones Areas with high current density for complex parts.

909838/1127 _BAD

Preferably, sulfate and fluoride-catalyzed baths are used, which mainly consist of OrO *, sulfate and silicon fluoride produced with self-regulating catalyst properties Arto described in U.S. Patents 2,640,021 and 2,640,022

The following examples serve as an explanation: "Trial" Pieces were electroplated as indicated in the table and checked for corrosion resistance

1. by the salt spray test (CASS) or

2. tested the Corrodkote test (GORK),

both by WoL.Pinner in the magazine Plating 44, 763. (1957), are described: »The values were determined by the ASTM method by H.A.Pray in the journal Proc ASTM, 49, 226 (1949) found

909838/1127

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909838/112 7

. - 10 -

U96896

From a consideration of the table it can be seen that the new products made according to the present invention are of high quality. It can also be seen that the presence the shiny, decorative outer coating according to the invention makes it possible to have a high collision capability Achieve, For example, by comparing Examples III and IV, one can see that if the thickness of the first layer is kept constant and the thickness of the outer chrome layer is increased from 0.36 micron to 1.91 micron, the corrosion resistance of the coating increases from 6 CORK from 23 hours to 251 CASS hours.

The same excellent ability of the outer layer to give better corrosion resistance can be seen by comparing Examples IV and Va Total thickness of the outer layer of the chrome coating, deposited according to the present invention, was increased from 0.36 microns (Example V) to 1.91 microns (Example IV) this results in an unexpected increase in the CASS time from 181 to 251 hours. This is an extraordinary one significant verbesaerungo

Another comparison that shows excellent results is achieved through the use of an external chrome layer applied according to the new method of the invention. One recognizes by comparison: he Examples VI and VII, according to which an increase in the thickness of the outer Layer from 1.27 micron to 3.81 micron takes place, an increase of the CORK-tfertes from 6 work steps to 19 work steps .

909838/1127 _{BAD 0R} , _G1N AL

H96896

The sulfate is generally added to the bath as strontium sulfate added the fluosilicate (SiPg ") as potassium or sodium salt. When replacing the fluosilicate compound in whole or in part with salts such as sodium fluoaluminate, ammonium fluoaluminate, Potassium fluozirconate and hydrated potassium fluotitanate, similar double chrome layers are obtained excellent corrosion resistance «, although the great corrosiveness is achieved by compound deposits in which the double layer of chromium is after of the invention is applied to an undercoat, it is still possible to use technically valuable double chromium plating. Divorces directly on the · base metals, for example Steel, nickel and nickel alloys, copper and copper alloys and the like. The base metal for use under a copper and / or nickel backing includes the wide range of conventional plated ones Metals such as steels, copper and copper alloys, nickel and nickel alloys, zinc and zinc alloys.

The new products produced by the present process can be the subject of one embodiment of the invention thus comprising a base metal with an electroplating thereon, the electroplating is characterized by its shiny and decorative appearance and its excellent corrosion resistance and wherein the electroplating comprises a primer layer of nickel, preferably with a thickness of at least about 20! ”ranon, especially from about 20-55 iuicron and one

BATH ORIGINAL 909838/1127

outer chrome layer of at least 0.5 micron and less than 5 microns thick with at least 10 cracks per cm · According to a Another embodiment can be the outer electroplated layer one ear layer with a thickness of at least 0.25 microns and a second layer with at least 10 cracks per cm and a thickness of at least 0.5 micron, the total thickness of the chrome plating at least about 1 micron and is less than 5 microns o

Since many embodiments of the present invention can be made without departing from the spirit and scope of the invention, it is intended that the invention be understood to include all variations and changes that come within the scope of the appended claims, _{or the like}

Claims

9 0 9 8 3 8/1127 SAD ORIGINAL

Claims (1)

Claims 1. A method for the galvanic deposition of shiny and corrosion-resistant double chromium coatings on a base metal, characterized in that first a chromium layer up to a thickness of at least 0.25 microns from a solution with an OrO ^ concentration between 150 and 525 g / liter and with sulfate- and fluoride-containing catalyst ions in such an amount that the ratio of GrO to the catalyst ions is between 110t1 and 175 * 1, the sulfate ions making up between 20 and 85 $ of the total amount of catalyst ions, at a temperature between 32 and 60 ⁰ G is deposited and then on the first chromium layer a layer of cracked chromium with at least 10 cracks per cm up to a thickness of at least 0.5 micron from a solution with a CrO ^ concentration between 150 and 450 g / liter and with sulfate and fluoride-containing catalyst ions are deposited in such an amount that the ratio of GrO "to the catalyst ions is between 50t1 and 100i 1, the sulfate ions being between $ 20 and $ 85 of the total catalyst ions, achieving a double layer of chromium with a total thickness of at least 1 micron and less than 5 microns. 2. The method "according to claim 1, characterized in that one dajs the first chrome layer with a thickness of at least 0.38 Micron and the second layer is applied in such a way that it contains at least 40 cracks per cm. ORIGINAL BATHROOM 909838/1127 - -H- U96896 The method according to claim 1, characterized in that one used fluosilicate as a catalyst component with fluoride ions Α » Process according to claim 1, characterized in that» fluoaluminate is used as the catalyst component with fluoride ions 5 »The method according to claim 1, characterized in that one used as a catalyst component with fluoride ions fluotitanate 6. The method according to claim 1, characterized in that one as a catalyst component with fluoride ions fluozirconate used" 7. Process for the electrodeposition of a corrosion-resistant double layer of chromium on one. Base metal, characterized in that a first chrome layer with a thickness of at least 0.25 microns from a solution with a CrO ^ concentration between 200 g and 400 g per liter at a temperature between 40 and 57 ⁰ C is applied, the Solution contains sulfate and fluoride catalyst ions in the ratio of CrO ^ to the catalyst ions between 120t1 and 1-5Qi 1, and the sulfate ions between 35 and 75 $ of the total catalyst ions, then a crack-containing second chromium layer on the first chromium layer ORiGSMAL BATHROOM 909838/11 27 with at least 10 cracks or cracks each om in one Strength of at least 0.5 Mioron from a solution with an OrO ^ concentration between 175 g and 300 g / liter "at a temperature between 43 and 55 ° G, this solution sulphate and fluoride catalyst ions in the Ver_ ratio of CrO., to the catalyst ions between 65s 1 and 90: 1, and the sulfate ions between $ 25 and $ 65 of the total catalyst ions, and the double chromium layer has a total thickness of at least 1 micron having. 8. The method according to claim 7, characterized in that the first chromium layer in a thickness of at least 0.38 Micron and the outer chrome layer is applied in such a way that it has at least 40 cracks per cm 9. A method for the electrolytic deposition of a corrosion-resistant double CLroraschicht on a G-round metal, characterized in that one first a first chromium layer with a thickness of at least 0.38 iilicron from a solution with a CrO ^ concentration between 200 g and 400 g each Liters at a temperature between 40 and 57 ° C, -.wherein the solution contains sulfate and fluoride catalyst ions in the ratio of CrO- to the catalyst ions between 120sl and 150: 1, and the sulfate ions between 35 and -d Ίογ-> der total catalyst ions, on the first chromium layer then a second chromium layer containing at least 40 cracks or ice creams per cm BADORIGJNAL 9 0 9 8 3 * I 1 T 2 7 ' - ie - ■. ■ U96896 ι 'in a strength of at least 1 micron aue a solution with an OrO, -concentration between 175 g and 300 g / liter at a temperature between 43 and 55 ^% O, with the solution sulfate and fluoride catalyst ions in the ratio of OrO, to contains the catalyst ions between 65 * 1 and 901, and the sulfate ions between 25 and 6556 of the total catalyst ions, and the double ear thickness has a total thickness of at least 1.5 microns. 10. The method according to claim 9, characterized in that ¹ the first ear layer is applied in a thickness of at least 1 million and the double chrome layer has a total thickness of at least 3.8 microns, 11. The method according to claim 9, characterized in that the catalyst component with fluoride ions used is fluosilicate 12. The method according to claim 9, characterized in that there is used as a catalyst component with fluoride ions fluoaluminate. 13. Process according to Claim 9, characterized in that fluotitanate is used as the catalyst component with fluoride ions. 14 »The method according to claim 9, characterized in thatman used as a catalyst component with fluoride ions fluozirconate, IO 909838/1127 - 17 - U96896 15 · Metal object with a decorative chrome coating and high corrosion resistance, characterized by an örundaohioht made of nickel with a thickness of about 20 million and an outer layer of chrome with a thickness of at least 0.5 million and less than 5 microns, which is at least 10 pieces per em having· 16 · Double decorative chrome coating with high corrosion resistance and a total thickness of at least 1 micron and less than a 5 mil a thickness of at least 0.5 Mioron. 909838/1127 ORiGiNAL INSPECTED