GB2056499A - Chemical Polishing Stainless Steel and Low Expansion Alloys - Google Patents
Chemical Polishing Stainless Steel and Low Expansion Alloys Download PDFInfo
- Publication number
- GB2056499A GB2056499A GB8027079A GB8022578A GB2056499A GB 2056499 A GB2056499 A GB 2056499A GB 8027079 A GB8027079 A GB 8027079A GB 8022578 A GB8022578 A GB 8022578A GB 2056499 A GB2056499 A GB 2056499A
- Authority
- GB
- United Kingdom
- Prior art keywords
- polishing
- bath
- stainless steel
- weight
- low expansion
- Prior art date
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Links
- 238000005498 polishing Methods 0.000 title claims abstract description 61
- 229910001220 stainless steel Inorganic materials 0.000 title claims abstract description 36
- 239000010935 stainless steel Substances 0.000 title claims abstract description 32
- 229910045601 alloy Inorganic materials 0.000 title claims abstract description 26
- 239000000956 alloy Substances 0.000 title claims abstract description 26
- 239000000126 substance Substances 0.000 title abstract description 13
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims abstract description 26
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims abstract description 24
- UMGDCJDMYOKAJW-UHFFFAOYSA-N aminothiocarboxamide Natural products NC(N)=S UMGDCJDMYOKAJW-UHFFFAOYSA-N 0.000 claims abstract description 22
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Natural products NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims abstract description 17
- -1 thiourea compound Chemical class 0.000 claims abstract description 15
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims abstract description 12
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims abstract description 12
- 229910017604 nitric acid Inorganic materials 0.000 claims abstract description 12
- 239000004094 surface-active agent Substances 0.000 claims abstract description 10
- 239000007864 aqueous solution Substances 0.000 claims abstract description 7
- 238000007517 polishing process Methods 0.000 claims abstract 3
- 238000000034 method Methods 0.000 claims description 22
- 125000000217 alkyl group Chemical group 0.000 claims description 13
- 229910052799 carbon Inorganic materials 0.000 claims description 13
- FLVIGYVXZHLUHP-UHFFFAOYSA-N N,N'-diethylthiourea Chemical compound CCNC(=S)NCC FLVIGYVXZHLUHP-UHFFFAOYSA-N 0.000 claims description 10
- 229910052739 hydrogen Inorganic materials 0.000 claims description 8
- 239000001257 hydrogen Substances 0.000 claims description 8
- 125000004435 hydrogen atom Chemical group [H]* 0.000 claims description 8
- KFFQABQEJATQAT-UHFFFAOYSA-N N,N'-dibutylthiourea Chemical compound CCCCNC(=S)NCCCC KFFQABQEJATQAT-UHFFFAOYSA-N 0.000 claims description 2
- 125000004432 carbon atom Chemical group C* 0.000 claims 4
- 230000009471 action Effects 0.000 abstract description 4
- 230000001133 acceleration Effects 0.000 abstract description 2
- 239000000243 solution Substances 0.000 description 34
- 229910052751 metal Inorganic materials 0.000 description 22
- 239000002184 metal Substances 0.000 description 22
- 239000000203 mixture Substances 0.000 description 20
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 18
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 10
- 239000000463 material Substances 0.000 description 9
- 229910000833 kovar Inorganic materials 0.000 description 8
- 229910052759 nickel Inorganic materials 0.000 description 8
- KQJQICVXLJTWQD-UHFFFAOYSA-N N-Methylthiourea Chemical compound CNC(N)=S KQJQICVXLJTWQD-UHFFFAOYSA-N 0.000 description 7
- 229910052742 iron Inorganic materials 0.000 description 7
- 150000003585 thioureas Chemical class 0.000 description 7
- 229910001374 Invar Inorganic materials 0.000 description 6
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- 150000001875 compounds Chemical class 0.000 description 6
- 239000008399 tap water Substances 0.000 description 6
- 235000020679 tap water Nutrition 0.000 description 6
- 150000002739 metals Chemical class 0.000 description 5
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 4
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- GQPLMRYTRLFLPF-UHFFFAOYSA-N Nitrous Oxide Chemical compound [O-][N+]#N GQPLMRYTRLFLPF-UHFFFAOYSA-N 0.000 description 4
- 239000004721 Polyphenylene oxide Substances 0.000 description 4
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 4
- 125000002877 alkyl aryl group Chemical group 0.000 description 4
- 238000005282 brightening Methods 0.000 description 4
- 150000001721 carbon Chemical group 0.000 description 4
- 239000011651 chromium Substances 0.000 description 4
- 229920000570 polyether Polymers 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 229910000990 Ni alloy Inorganic materials 0.000 description 3
- 239000002253 acid Substances 0.000 description 3
- 229910052804 chromium Inorganic materials 0.000 description 3
- 239000010941 cobalt Substances 0.000 description 3
- 229910017052 cobalt Inorganic materials 0.000 description 3
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 3
- 239000000470 constituent Substances 0.000 description 3
- 238000006731 degradation reaction Methods 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
- 239000004615 ingredient Substances 0.000 description 3
- 230000001590 oxidative effect Effects 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 2
- MNOILHPDHOHILI-UHFFFAOYSA-N Tetramethylthiourea Chemical compound CN(C)C(=S)N(C)C MNOILHPDHOHILI-UHFFFAOYSA-N 0.000 description 2
- 239000003929 acidic solution Substances 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 2
- 150000007513 acids Chemical class 0.000 description 2
- 239000004480 active ingredient Substances 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- VQLYBLABXAHUDN-UHFFFAOYSA-N bis(4-fluorophenyl)-methyl-(1,2,4-triazol-1-ylmethyl)silane;methyl n-(1h-benzimidazol-2-yl)carbamate Chemical compound C1=CC=C2NC(NC(=O)OC)=NC2=C1.C=1C=C(F)C=CC=1[Si](C=1C=CC(F)=CC=1)(C)CN1C=NC=N1 VQLYBLABXAHUDN-UHFFFAOYSA-N 0.000 description 2
- GMEGXJPUFRVCPX-UHFFFAOYSA-N butylthiourea Chemical compound CCCCNC(N)=S GMEGXJPUFRVCPX-UHFFFAOYSA-N 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- 239000011572 manganese Substances 0.000 description 2
- 239000001272 nitrous oxide Substances 0.000 description 2
- 229910000029 sodium carbonate Inorganic materials 0.000 description 2
- GPRLSGONYQIRFK-MNYXATJNSA-N triton Chemical compound [3H+] GPRLSGONYQIRFK-MNYXATJNSA-N 0.000 description 2
- CDQKAMJCEHHDSB-UHFFFAOYSA-N 1-ethyl-1-methylthiourea Chemical compound CCN(C)C(N)=S CDQKAMJCEHHDSB-UHFFFAOYSA-N 0.000 description 1
- 239000010963 304 stainless steel Substances 0.000 description 1
- 229910000619 316 stainless steel Inorganic materials 0.000 description 1
- 239000010965 430 stainless steel Substances 0.000 description 1
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910000599 Cr alloy Inorganic materials 0.000 description 1
- IAYPIBMASNFSPL-UHFFFAOYSA-N Ethylene oxide Chemical compound C1CO1 IAYPIBMASNFSPL-UHFFFAOYSA-N 0.000 description 1
- 229910000640 Fe alloy Inorganic materials 0.000 description 1
- VLCDUOXHFNUCKK-UHFFFAOYSA-N N,N'-Dimethylthiourea Chemical compound CNC(=S)NC VLCDUOXHFNUCKK-UHFFFAOYSA-N 0.000 description 1
- 229910000589 SAE 304 stainless steel Inorganic materials 0.000 description 1
- 101100391171 Schizosaccharomyces pombe (strain 972 / ATCC 24843) for3 gene Proteins 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- XSTXAVWGXDQKEL-UHFFFAOYSA-N Trichloroethylene Chemical group ClC=C(Cl)Cl XSTXAVWGXDQKEL-UHFFFAOYSA-N 0.000 description 1
- 229920004890 Triton X-100 Polymers 0.000 description 1
- 239000013504 Triton X-100 Substances 0.000 description 1
- 229920004896 Triton X-405 Polymers 0.000 description 1
- 125000001931 aliphatic group Chemical group 0.000 description 1
- 229910002065 alloy metal Inorganic materials 0.000 description 1
- 239000010953 base metal Substances 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000007859 condensation product Substances 0.000 description 1
- 230000001143 conditioned effect Effects 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 238000005238 degreasing Methods 0.000 description 1
- XXBDWLFCJWSEKW-UHFFFAOYSA-N dimethylbenzylamine Chemical compound CN(C)CC1=CC=CC=C1 XXBDWLFCJWSEKW-UHFFFAOYSA-N 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 239000004519 grease Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 239000012286 potassium permanganate Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- UBOXGVDOUJQMTN-UHFFFAOYSA-N trichloroethylene Natural products ClCC(Cl)Cl UBOXGVDOUJQMTN-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F3/00—Brightening metals by chemical means
- C23F3/04—Heavy metals
- C23F3/06—Heavy metals with acidic solutions
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- ing And Chemical Polishing (AREA)
Abstract
A bath for chemically polishing of a stainless steel or low expansion alloy surface, said bath comprising an aqueous solution containing 1% to 20% by weight of hydrochloric acid, 1% to 10% by weight of nitric acid, 0 to 60% by weight of phosphoric acid, 0.01%to 20% by weight of a surfactant, and at least 0.01% by weight of a thiourea compound and a method of polishing employing said bath. The thiourea compound causes significant acceleration in the chemical polishing action.
Description
SPECIFICATION
Chemical Polishing Stainless Steel and Low Expansion Alloys
This invention relates to a composition for chemically polishing metals and to a method using such composition. More particularly, the invention relates to a method of chemically polishing stainless steel and low expansion alloy surfaces and to a composition useful for such method.
Methods for descaling, polishing and brightening stainless steel and low expansion alloy metals include mechanical polishing and buffing, electropolishing and chemical polishing. Mechanical polishing involves extensive handling of an object, resulting in high labour costs, and often such polishing cannot be performed at all because of the intricate form and nature of an object requiring polishing. In addition, electropolishing is not suitable for objects which have deep recesses or interior surfaces requiring polishing. Although certain chemical polishing baths as well known for brightening stainless steel and low expansion alloys, some of these baths produce a grainy or satiny surface as opposed to a highly polished surface; others are rather sensitive to changes in the concentrations of the active ingredients and are therefore difficult to control.In addition, the concentration of the active ingredients in these brightening baths is generally quite high, resulting in high "drag-out" losses, i.e.
the material clings to the article being polished and is lost or transferred as a contaminant to subsequent processing operations. Moreover, the prior chemical polishing baths have a tendency to remove unduly large quantities of metal from the article and thus adversely affect the dimensional tolerances of the polished surfaces which is a matter of great concern in many instances. In the electronics industry, for example, where a number of low expansion metals are used, only very small amounts of metal can be removed without adversely affecting the performance of the electronic component.
U.S. Patent No. 3,072,515 discloses a method and composition for descaling and chemically polishing metals, particularly stainless steel. The metal surface is contacted with an aqueous solution of hydrochloric acid, nitric acid and a surfactant having a polyoxyethylene chain in its molecule, as more particularly described in the patent. The solution may also contain phosphoric acid to enhance the action of the ingredients. The metal surface is polished to a near mirror finish while dissolutiqn of the base metal and "drag-out" are minimized.
Additionally, U.S. Patent No. 3,457,107 discloses a method and composition for descaling and chemically polishing metals, particularly stainless steel, wherein the metal surface is first contacted with an alkaline oxidizing descaling composition followed by a suitable acidic aqueous solution and then chemically polished by contacting said surface with a composition consisting essentially of water, hydrochloric acid, nitric acid, phosphoric acid and a surfactant selected from the recited groups of ethylene oxide condensation products and aliphatic surfactants.
While the methods and compositions as taught by Patents No.3,072,515 and 3,457,107 produce acceptable results on the 300 Series of stainless steel, i.e. those containing relatively large amounts of chromium and nickel, the brightness obtained on other alloys within the stainless steel group is significantly less and in most cases can only be described as a somewhat reflective satin finish. In addition, when using these compositions, relatively long processing times are necessary in order to obtain high degrees of polishing and brightness.
U.S. Patent No. 3,530,017 discloses the chemical polishing of low expansion alloys using the same baths described above for polishing stainless steel. The baths, however, exhibit similar shortcomings in that, while very bright and smooth surfaces are produced on low expansion alloys with relatively low nickel content, the brightness obtained on high nickel alloys is significantly less.
it is an object of the present invention to provide improved brightness and polish on stainless steels, including the 400 Series stainless steels which are generally recognized as being difficult to chemically polish to a high lustre.
Another object of the present invention is to provide improved brightness and polish on low expansion alloys.
Another object of the present invention is to provide a composition which significantly reduces the processing time required for chemically polishing stainless steels while producing very satisfactory degrees of brightness and polish.
The term "stainless steel" as used herein is meant to cover those metals which are mainly alloys of iron, chromium and nickel along with other minor alloying constituents, or of iron and chromium and other minor alloying constituents.
The term "low expansion alloy" as used herein refers to special alloys used primarily in the electronics industry where their low expansion properties are compatibile with other materials to which they are joined and produce strong and leak-proof junctures.
Representative low expansion alloys can be essentially all nickel with small amounts of other ingredients, but usually are alloys composed of nickel and iron; iron and cobalt; and nickel, iron and cobalt with or without small amounts of other minor constituents. Chromium may be present, but usually not in amounts exceeding 5% of the total composition. The entire disclosure of low expansion alloys found in U.S. Patent No. 3,530,017 is incorporated herein by reference.
Specific commercially used examples of the low expansion alloys would be:
a) "Kovar" Registered Trade Mark, which has a composition of:
Per cent by weight
Nickel 29
Cobalt 17
Manganese 0.45 Siiicon 0.10
Carbon 0.02
Iron Remainder
b) "Invar" Registered Trade Mark, which has a composition of:
Per cent by weight
Iron 63.8
Nickel 36.0
Carbon 0.2
c) "Grade 200 Nickel Alloy" which has a composition of:
Per cent by weight
Nickel 99.435
Carbon 0.06
Manganese 0.25
Iron 0.15
Sulfur 0.005
Silicon 0.05
Copper 0.05
In the Examples and in the appended claims the concentrations of acids are expressed as percentby weight of the total bath, with the acids being considered of 100% strength.
It has now 6een discovered in accordance with the present invention, that chemical polishing of stainless steel can be significantly improved by the inclusion of a thiourea compound in an acidic bath used for chemically polishing stainless steels, including those disclosed in U.S. Patent Nos. 3,072,515 and 3,457,107 and 3,530,017, resulting in significant improvements in brightness and polish, and increased polishing action.
Prior to carrying out the process of the invention on stainless steel, the stainless steel surface is desirably first subjected to a pretreatment which conditions the surface prior to chemically polishing.
As fully described in U.S. Patent No. 3,457,107 this treatment consists in contacting the stainless steel metal surface with an aqueous alkaline oxidizing solution which serves to condition the metal surface and prepares it for oxide removal and subsequent chemical polishing.
Low expansion alloys are pre-conditioned according to the methods taught in U.S. Patent No.
3,530,017 whereby residual contamination of oxides are removed by treatment with various acidic solutions prior to polishing and brightening. Thus, the expansion alloy surface can be degreased and then descaled with 28% hydrochloric acid.
The pretreated stainless steel or low expansion alloy surface then may be contacted, according to the invention, with an aqueous solution containing water, hydrochloric acid, nitric acid, a surfactant and a compound belonging to the general class of thioureas. The solution may also contain phosphoric acid.
Any suitable surfactant can be used. More particularly, the surfactant may be a compound having a polyoxyethylene chain in its molecule, or it may be one of the class of compounds as defined in U.S.
Patents Nos. 3,457,107 and 3,530,017. Other suitable surfactants also can be used.
Any thiourea compound containing the group
can be used in the invention provided as it significantly accelerates chemical polishing of stainless steel and low expansion alloys and is sufficiently stable in the polishing bath to be useful. Thiourea compounds which contain no hydroxy substituents are preferred. Some thiourea compounds which are particularly useful have the general formula
wherein R1 is hydrogen or an alkyl group having at least one carbon atom in the chain, R2 is hydrogen or an alkyl group having at least one carbon atom in the chain, R3 is hydrogen or an alkyl group having at least one carbon atom in the chain and R4 is hydrogen or an alkyl group having at least one carbon atom in the chain.The alkyl groups will generally have no more than twelve carbons in a straight or branched chain and usually the alkyl groups will be lower alkyl groups having no more than six to eight carbons in a straight or branched chain. Furthermore, there is generally no advantage in using thiourea derivatives having one or more alkyl groups with more than four carbons in a chain. At present, it appears that the most useful compounds are thiourea and monoalkyl thiourea and dialkyl thioureas, and especially those having both alkyls on the same nitrogen. Representative examples of these compounds are well known and include such compounds as thiourea, methylthiourea, methylethylthiourea, diethylthiourea, dibutylthiourea, dimethylthiourea and butylthiourea.
The thiourea compounds, when used in accordance with this invention, cause a significant acceleration in the chemical polishing action of the solution described above. While the exact mechanism is not known, it is believed that the thiourea compounds have the unique ability to promote a controlled degradation of the nitric acid component contained in the polishing solution. This degradation causes a much higher formation of nitrous oxide which is the major ingredient responsible for attack on metal surfaces when using polishing baths such as have been described. The degradation reaction is a stable one and does not occur unless a metal surface is introduced into the polishing solution, at which point the formation of corrosive nitrous oxide begins. This same reaction ceases when the metal surface is removed from the polishing solution.The end results of such accelerated polishing solutions are that stainless steel and low expansion alloy surfaces are able to be chemically polished to a much higher lustre and in a relatively shorter time than has been previously possible when using polishing solutions previously known to those familiar with the methods of chemical polishing.
According to the invention, the stainless steel or low expansion alloy surface can be contacted with an aqueous solution containing 120% by weight of hydrochloric acid, 1-10% by weight of nitric acid, 0-60% by weight of phosphoric acid, 0.01-20% by weight of a surfactant and at least 0.01% by weight of a thiourea compound. Usually no more than 10%, and generally no more than 5% by weight of a thiourea compound need be used in the bath. When phosphoric acid is included, a minimum of 5% is desirably added.
The metal to be polished is contacted with the polishing solution at an elevated temperature and for a period of time sufficient to produce a brightly polished surface. The bath is maintained at a temperature desirably in the range of 540C-930C (130--2000F.), and preferably at 71 0C-880C (160-1 900 F). The time required to produce a brightly polished surface varies depending on the temperature of the polishing solution, the composition of the polishing solution, the type of metal to be polished, and the condition of the metal surface.Ordinarily the time required for polishing is about 210 minutes at a temperature in the range of 71 OC--880C (160-1 900F.), with the time decreasing at increased temperatures and increasing at decreased temperatures. Following the polishing treatment the metal surface is simply rinsed with clean water and dried. No further treatment is necessary.
The following examples illustrate the invention:- Example 1
A panel of 24 gauge stainless steel, Type 304 having a 28 (matte) mill finish and specular reflectance of 30% was cleaned to remove oil and grease by immersing it for 10 minutes at 820C (1 800 F). in an aqueous solution containing a concentration of 45 g/litre (6 oz/gal.) of a cleaner having the following composition:
Material Per cent by weight
Sodium hydroxide 50
Sodium carbonate 47
Triton X-100 (alkyl aryl) polyether alcohol) 3
The panel was removed from the solution, thoroughly rinsed with tap water and then immersed for 15 minutes in the following alkaline oxidizing solution at 930C (2000 F):: Material Per cent by weight
Sodium hydroxide 8.0
Potassium permanganate 2.5
Sodium carbonate 1.0
Water 88.5
The panel was then removed from the solution, thoroughly rinsed with tap water and then immersed for 5 minutes in the following aqueous acidic solution at 240C (75"F): Material Per cent by weight
Hydrochloric acid (100%) 10 Xyiene suphonic acid 0.5
Water 89.5
The panel was removed from the solution and thoroughly rinsed with tap water.The now
chemically clean and deoxidized Type 304 stainless steel panel was immersed for 7 minutes at 770C (1700 F) in the following polishing solution:
Material Per cent by weight
Hydrochloric acid 3.5
Nitric acid 1.5
Phosphoric acid 26.5
Alkyl aryl polyether alcohol' 1.0
Methylthiourea 0.2
Water 67.3
'Triton X-1 00 Registered Trade Mark, (Rohm s Haas Co.)
The panel was removed from the polishing solution, thoroughly rinsed with tap water, dried and inspected. The surface of the panel was uniformly polished to a high near-mirror finish. Per cent specular reflectance was 78%. Specular reflectance is measured by means of a reflectometer using a mirror as standard (100%).
A second panel of24 gauge stainless steel, Type 304 having a 2B (matte) mill finish was cleaned and deoxidized using the same procedures as above. The panel was then immersed in an identical polishing bath as above for the same time and at the same temperature except that methylthiourea was omitted from the polishing solution.
The panel was uniformly polished but had a specular reflectance of only 57% versus a mirror surface.
Example 2
A panel of 24 gauge stainless steel, Type 31 6 having a 28 (matte) finish and a specular reflectance of 26%, was cleaned and polished using the procedure of Example 1 except that the polishing solution contained 4% by weight of nitric acid instead of 1.5%. The stainless steel panel was uniformly and highly polished. It had a specular reflectance of 67%.
An identical panel of Type 316 stainless steel was cleaned and polished using the same procedure as above except that methylthiourea was omitted from the polishing solution. The panel was uniformly polished but had a specular reflectance of only 49%.
Example 3
Example 1 was repeated using 0.5% by weight of thiourea in place of methylthiourea. Equivalent results were obtained.
Example 4
Using panels of 24 gauge stainless steel, Type 430 having a 28 (matte) finish and a specular reflectance of 33%, Example 1 was repeated using diethylthiourea in a polishing solution having the following composition:
Material Per cent by weight
Hydrochloric acid 5.0
Nitric acid 2.7
Phosphoric acid 26.0 1-hydroxyethyl-2-heptadecenyl1 glyoxalidine salt 1.0
Sodium lauryl sulfate2 0.8
Diethylthiourea 0.2
Water 64.3 gamine O (Ciba-Geigy)
2Duponal C (DuPont Co.)
The stainless steel panels were uniformly and highly polished. They had a specular reflectance of
61%.
A second set of identical Type 430 stainless steel panels was cleaned and polished using the
same procedure and solutions as above except that diethylthiourea was omitted from the polishing
solution. The panels were uniformly polished but had a specular reflectance of only 47%.
Example 5
Using Type 202 stainless steel panels with a 2B (matte) finish and a specular reflectance of 33%,
the procedure of Example 1 was repeated, employing instead a polishing solution with the following
composition:
Material Per cent by weight
Hydrochloric acid 4.0 Nitric acid 4.0
Phosphoric acid 24.0
Alkylaryl polyether alcohol' 1.0 n-Alkyl (50%C,,, 40%C,,, 10%Cia) dimethyl benzyl ammonium chloride2 0.7 1,1 ,3,3-tetramethyl-2-thiourea 0.4 Water 65.9
'Triton X-405 (Rohm 8 Haas Co.)
2Hyamine 3500 (Rohm 8 Haas Co.)
The stainless panels were uniformly and highly polished. They had a specular reflectance of 71%.
A second set of identical Type 202 stainless steel panels were cleaned and polished using the same procedure and solution as above except that the 1,1 ,3,3-tetramethyl-2-thiourea was omitted from the polishing solution. The panels were uniformly polished but had a specular reflectance of only 56%.
Example 6 A strip of the low expansion alloy known as Kovar, with the above composition, and having a noticeable blue-black heat scale on its surface from previous heat treating, was cleaned by vapour degreasing using trichloroethylene and then immersed in a 50:50 by volume solution of hydrochloric acid (28%) and water at 52 OC (1 250F) for 2 minutes and rinsed with cold tap water. The Kovar strip was now scale free but the surface had a dull silver-grey and grainy appearance.
The descaled Kovar strip was then immersed in a polishing bath of the following composition, at 800C (1750F)for3 minutes: Material Per cent by weight
Hydrochloric acid 4.0 Nitric acid 2.0
Phosphoric acid 30.0
Alkyl aryl polyether alcohol' 1.0
Stearyl-methyl-polyoxyethyl ammonium chloride2 0.7
Diethylthiourea 0.2
Water 62.1
'Triton X-1 00 (Rohm & Haas)
2Ethoquad 18/25 (Armak Chemicals)
The Kovar strip was removed from the polishing solution, thoroughly rinsed with tap water, dried
and inspected. The metal surface was very bright and showed no sign of pitting or non-uniformity
when inspected under magnification.
A second strip of identical low expansion metal was cleaned and descaled using the same
procedures as above. The panel was then immersed in an identical polishing bath as above for the
same time and at the same temperature except that diethylthiourea was omitted from the polishing
solution.
The Kovar strip was only partially polished, still showing evidence of a remaining silver-grey
surface. The surface under magnification appeared to be incompletely polished.
The same Kovar strip was re-immersed in the polishing solution at the above conditions for an
additional 3 minutes. After a total of 6 minutes polishing time the Kovar strip was polished to the same
degree as that done with the diethylthiourea containing solution.
Example 7
An article consisting of Invar bonded to glass was cleaned, descaled and polished using the same
procedure as in Example 6 except that 0.2% by weight of methylthiourea was substituted for
diethylthiourea and the total contact time in the polishing solution was 2 minutes.
The Invar surface was highly polished and uniform in appearance with no evidence of pitting.
There was no selective etching or evidence of higher metal removal in the area of the glass to Invar
bond.
An identical article composed of Invar bonded to glass was polished using the same procedure as
above but with the exception that the methylthiourea was omitted from the polishing solution. The
Invar surface was not as highly polished nor as uniform as the first article when using diethylthiourea.
Claims (12)
1. A bath for chemically polishing of a stainless steel or low expansion alloy surface, said bath comprising an aqueous solution containing 1% to 20% by weight of hydrochloric acid, 1% to 10% by weight of nitric acid, 0 to 60% by weight of phosphoric acid, 0.01% to 20% by weight of a surfactant, and at least 0.01% by weight of a thiourea compound.
2. A bath as claimed in Claim 1, in which the thiourea compound has no hydroxy substituent.
3. A bath as claimed in Claim 1 or 2 containing 5 to 60% by weight of phosphoric acid.
4. A bath as claimed in any of Claims 1 to 3 in which the thiourea compound has the formula
wherein R1 is hydrogen or an alkyl group having at least one carbon atom in its chain, R2 is hydrogen or an alkyl group having at least one carbon atom in its chain, R3 is hydrogen or an alkyl group having at least one carbon atom in its chain and R4 is hydrogen or an alkyl group having at least one carbon atom in its chain.
5. A bath as claimed in Claim 4 in which the thiourea compound is thiourea.
6. A bath as claimed in Claim 4 in which the thiourea compound is dibutylthiourea.
7. A bath as claimed in Claim 4 in which the thiourea compound is diethylthiourea.
8. A bath as claimed in Claim 1 substantially as herein described with reference to the Examples.
9. A method of polishing a stainless steel or low expansion alloy surface comprising contacting said surface with a bath as claimed in any of Claims 1 to 8 under conditions of time and temperature sufficient to produce a brightly polished surface.
10. A method as claimed in Claim 9 in which the temperature is within the range of from 591 930C.
11. A method as claimed in Claim 9 in which the temperature is within the range of from 71- 88"C.
12. A method of polishing a stainless steel or low expansion alloy surface substantially as herein described with reference to the Examples.
1 3. A stainless steel or low expansion alloy the surface of which has been polished by a method as claimed in any of Claims 9-12.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2931558A DE2931558A1 (en) | 1979-08-03 | 1979-08-03 | METHOD FOR PRODUCING A Sintered Steel Alloy |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2056499A true GB2056499A (en) | 1981-03-18 |
Family
ID=6077568
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8027079A Withdrawn GB2056499A (en) | 1979-08-03 | 1980-07-10 | Chemical Polishing Stainless Steel and Low Expansion Alloys |
Country Status (3)
| Country | Link |
|---|---|
| DE (1) | DE2931558A1 (en) |
| GB (1) | GB2056499A (en) |
| SE (1) | SE8005366L (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2288190A (en) * | 1994-04-08 | 1995-10-11 | Wonder Wheels | Cleaning composition containing hydrochloric acid |
| CN110219004A (en) * | 2019-07-08 | 2019-09-10 | 周兆梅 | A kind of aluminum alloy chemically polishing fluid and its polishing method |
| CN113584488A (en) * | 2021-07-20 | 2021-11-02 | 遵义智通金属表面技术处理有限公司 | Kovar alloy (4J29) normal-temperature chemical polishing method |
| CN114059068A (en) * | 2021-11-15 | 2022-02-18 | 陕西金信天钛材料科技有限公司 | Chemical and electrochemical plasma composite polishing method for surface of heart scaffold |
| CN114096697A (en) * | 2019-07-15 | 2022-02-25 | 赛峰飞机发动机公司 | Composition, use thereof for pickling magnesium alloys and method for pickling magnesium alloys |
-
1979
- 1979-08-03 DE DE2931558A patent/DE2931558A1/en not_active Withdrawn
-
1980
- 1980-07-10 GB GB8027079A patent/GB2056499A/en not_active Withdrawn
- 1980-07-24 SE SE8005366A patent/SE8005366L/en unknown
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2288190A (en) * | 1994-04-08 | 1995-10-11 | Wonder Wheels | Cleaning composition containing hydrochloric acid |
| CN110219004A (en) * | 2019-07-08 | 2019-09-10 | 周兆梅 | A kind of aluminum alloy chemically polishing fluid and its polishing method |
| CN114096697A (en) * | 2019-07-15 | 2022-02-25 | 赛峰飞机发动机公司 | Composition, use thereof for pickling magnesium alloys and method for pickling magnesium alloys |
| CN113584488A (en) * | 2021-07-20 | 2021-11-02 | 遵义智通金属表面技术处理有限公司 | Kovar alloy (4J29) normal-temperature chemical polishing method |
| CN114059068A (en) * | 2021-11-15 | 2022-02-18 | 陕西金信天钛材料科技有限公司 | Chemical and electrochemical plasma composite polishing method for surface of heart scaffold |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2931558A1 (en) | 1981-02-12 |
| SE8005366L (en) | 1981-02-04 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |