US2894850A - Method of galvanizing ferrous metal strip - Google Patents
Method of galvanizing ferrous metal strip Download PDFInfo
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- US2894850A US2894850A US735316A US73531658A US2894850A US 2894850 A US2894850 A US 2894850A US 735316 A US735316 A US 735316A US 73531658 A US73531658 A US 73531658A US 2894850 A US2894850 A US 2894850A
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- galvanizing
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- 238000000034 method Methods 0.000 title claims description 24
- 238000005246 galvanizing Methods 0.000 title claims description 23
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 title claims description 18
- 229910052751 metal Inorganic materials 0.000 title description 27
- 239000002184 metal Substances 0.000 title description 27
- 239000011248 coating agent Substances 0.000 claims description 27
- 238000000576 coating method Methods 0.000 claims description 27
- -1 ALKALI METAL ALUMINATE Chemical class 0.000 claims description 21
- 229910052783 alkali metal Inorganic materials 0.000 claims description 20
- 230000008569 process Effects 0.000 claims description 16
- 238000001035 drying Methods 0.000 claims description 15
- 238000007598 dipping method Methods 0.000 claims description 11
- ANBBXQWFNXMHLD-UHFFFAOYSA-N aluminum;sodium;oxygen(2-) Chemical compound [O-2].[O-2].[Na+].[Al+3] ANBBXQWFNXMHLD-UHFFFAOYSA-N 0.000 description 19
- 229910001388 sodium aluminate Inorganic materials 0.000 description 19
- 239000000243 solution Substances 0.000 description 19
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 15
- 229910052725 zinc Inorganic materials 0.000 description 15
- 239000011701 zinc Substances 0.000 description 15
- 239000000080 wetting agent Substances 0.000 description 11
- 229910000831 Steel Inorganic materials 0.000 description 9
- 239000010959 steel Substances 0.000 description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 9
- 230000001680 brushing effect Effects 0.000 description 6
- 238000004140 cleaning Methods 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 150000004645 aluminates Chemical class 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 238000010276 construction Methods 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 239000012670 alkaline solution Substances 0.000 description 2
- 238000005238 degreasing Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 230000001681 protective effect Effects 0.000 description 2
- 238000007789 sealing Methods 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- JNYAEWCLZODPBN-JGWLITMVSA-N (2r,3r,4s)-2-[(1r)-1,2-dihydroxyethyl]oxolane-3,4-diol Chemical compound OC[C@@H](O)[C@H]1OC[C@H](O)[C@H]1O JNYAEWCLZODPBN-JGWLITMVSA-N 0.000 description 1
- JHWIEAWILPSRMU-UHFFFAOYSA-N 2-methyl-3-pyrimidin-4-ylpropanoic acid Chemical compound OC(=O)C(C)CC1=CC=NC=N1 JHWIEAWILPSRMU-UHFFFAOYSA-N 0.000 description 1
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- 229920003171 Poly (ethylene oxide) Polymers 0.000 description 1
- 229920001213 Polysorbate 20 Polymers 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 229910052910 alkali metal silicate Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 description 1
- 239000010425 asbestos Substances 0.000 description 1
- 239000010953 base metal Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052793 cadmium Inorganic materials 0.000 description 1
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 1
- 229910052792 caesium Inorganic materials 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 239000003518 caustics Substances 0.000 description 1
- 238000011437 continuous method Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 239000003599 detergent Substances 0.000 description 1
- 238000010494 dissociation reaction Methods 0.000 description 1
- 230000005593 dissociations Effects 0.000 description 1
- 238000005755 formation reaction Methods 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 239000003112 inhibitor Substances 0.000 description 1
- KFZAUHNPPZCSCR-UHFFFAOYSA-N iron zinc Chemical compound [Fe].[Zn] KFZAUHNPPZCSCR-UHFFFAOYSA-N 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- YQNQTEBHHUSESQ-UHFFFAOYSA-N lithium aluminate Chemical compound [Li+].[O-][Al]=O YQNQTEBHHUSESQ-UHFFFAOYSA-N 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 238000010422 painting Methods 0.000 description 1
- 235000010486 polyoxyethylene sorbitan monolaurate Nutrition 0.000 description 1
- 239000000256 polyoxyethylene sorbitan monolaurate Substances 0.000 description 1
- 229920001451 polypropylene glycol Polymers 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- 238000011946 reduction process Methods 0.000 description 1
- 229910052895 riebeckite Inorganic materials 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 229910052701 rubidium Inorganic materials 0.000 description 1
- IGLNJRXAVVLDKE-UHFFFAOYSA-N rubidium atom Chemical compound [Rb] IGLNJRXAVVLDKE-UHFFFAOYSA-N 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
Images
Classifications
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- 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
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
- C23C2/022—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by heating
- C23C2/0222—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by heating in a reactive atmosphere, e.g. oxidising or reducing atmosphere
-
- 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
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/003—Apparatus
- C23C2/0034—Details related to elements immersed in bath
- C23C2/00342—Moving elements, e.g. pumps or mixers
- C23C2/00344—Means for moving substrates, e.g. immersed rollers or immersed bearings
-
- 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
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/003—Apparatus
- C23C2/0035—Means for continuously moving substrate through, into or out of the bath
-
- 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
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/003—Apparatus
- C23C2/0038—Apparatus characterised by the pre-treatment chambers located immediately upstream of the bath or occurring locally before the dipping process
-
- 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
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
- C23C2/024—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by cleaning or etching
Definitions
- This invention relates to a method of coating a base metal with another molten metal and more particularly to a method of galvanizing ferrous metal strip or sheet material on one side only.
- Galvanized sheet metal is conventionally used in applications where the metal must necessarily be exposed to the corrosive effects of the elements and the like. It has been considered for use in automobile body construction to improve corrosion resistance, particularly on the interior surfaces of the body where rusting is generally most severe.
- commercial galvanized sheet which is zinc coated on both sides, has never been generally accepted for automobile body construction on a commercial basis because of complications arising from the adherence of zinc to the electrode tips in the process of resistance welding the galvanized parts together.
- the surface quality of galvanized sheet for exterior body surfaces is generally inferior to bare sheet steel.
- a process including the steps of first cleaning or degreasing the sheet material by any well-known manner; coating one side of the sheet with an alkali metal aluminate solution, preferably containing small quantities of a suitable nonionic wetting agent which will not dissociate in a strongly alkaline solution; drying the alkali metal aluminate coated sheet; subjecting the dried sheet to a reducing atmosphere at temperatures ranging from about 1250 F.
- a steel sheet is first cleaned by dipping it in a cleaning bath containing a suitable detergent.
- Any well-known degreasingor cleaning method such as by means of an electrolytic caustic solution or vapor degreasing, may be used.
- an aqueous alkali metal aluminate solution preferably containing small quantities of a suitable wetting agent.
- An alkali metal aluminate coating of a thickness of .001 to .002 inch has been found satisfactory.
- the solution may be suitably applied by brushing. However, other methods of application, such as spraying or rolling may also be used.
- a preferred solution for this purpose is an aqueous solution containing about 20% sodium aluminate (NaAlO and about 0.3%
- sodium aluminate solutions as low as 5% may be used. Solutions below 5% are undesirable, since below this concentration the sodium aluminate tends to dissociate to sodium hydroxide and precipitated aluminum oxide with a result that these materials would be undesirably applied to the steel sheet. Higher concentrations of the sodium aluminate are also suitable, such higher concentrations being limited by the saturation characteristics of the sodium aluminate.
- Other alkali metal aluminates may also be used in place of the sodium aluminate as well as mixtures of alkali metal aluminates. Sodium and potassium aluminates are preferred because of their availability and high water solubility.
- Lithium aluminate is less desirable because of its low solubility in water while other alkali metal aluminates, such as rubidium and cesium aluminate are of limited use, as a practical matter, due to the scarcity and relatively high cost of these alkali metals.
- wetting agents of the non-ionic type which are not subject to dissociation in strong alkaline solutions are suitable.
- wetting agents which have been successfully used include sorbitan mohooleate and mixtures of polyethylene oxide and polypropylene oxide.
- the Wetting agent is preferably presentin small but effective amounts, such as will permit an ethcient application of the alkali metal aluminate solution to the cleaned sheet metal.
- the sheet is preferably subjected to heat at temperatures ranging from 250 F. to 300 F. for a time sufficient to cause the sodium aluminate coating to dry. It has been found that drying temperatures up to 700 F. may also be used in the drying step whereby a very rapid drying may be accomplished. Experimental tests have indicated that the sodium aluminate coating, dried and baked at 600 F. to 700 F., involves an oxidation of the steel beneath the sodium aluminate coating but that this oxide is reduced so as to' provide a clean steel sheet in a subsequent reduction process, as will be hereinafter described.
- the sheet is then placed in a reducing atmosphere heated to about 1400 F. for about 5 minutes or a time sufficient to remove all oxides from the metal. Reducing temperatures ranging from 1250 F. to 1450 F. may be satisfactorily used with an appropriate adjust ment in time.
- a reducing atmosphere of hydrogen having a dew point of F. has been found highly satisfactory for the purpose.
- Another suitable reducing atmosphere includes typically 12.5% hydrogen, 10.5% carbon monoxide, 5.0% carbon dioxide, 0.5% methane, 0.8% water, and 70.7% nitrogen.
- Another suitable re ducing atmosphere which may be used is cracked ammonia having a dew point of about 80 F.
- the sheet metal After the sheet metal has been suitably exposed to the reducing atmosphere so as to fully remove any oxidized surface thereon and While still under the protective reducing atmosphere, it is dipped for about 5 to 30 seconds into molten zinc maintained at about 850 F. 'After the dipping step the sheet is permitted to cool and the coating to solidify by guiding it a sufficient distance in the atmosphere. The sodium aluminate coating is removed by a simple water rinse and brushing operation.
- an important aspect of this invention resides in the use of the alkali metal aluminate solution which will remain adhered to the metal sheet during the galvanizing process, prevent the adherence of the zinc to the aluminate coated portions of the sheet metal and be readily removed by a simple operation such as brushing so as to provide a clean ferrous metal surface which is readily amendable to Welding operations and the reception of surface coating such as paint and the like. No other material has been found which will prevent the adherence of zinc and yet be readily removed after being subjected to the reducing heat treatment of 1250 F. or more.
- Sheet -metal or strip is provided in the form of a roll mounted on a suitable rotatable supporting mechanism 12.
- the sheet is guided by suitable rollers 14, 16, 18 and 20, and continuously passed into and out of a cleaning bath 22 contained in tank 24.
- the tank 24 is, of course, suffi- -ciently large to permit the sheet metal to be adequately cleaned as it passes through.
- the sheet is passed over a roller 26 which is partially submerged in a sodium aluminate solution 28 contained in a tank 30, whereby the underside of the sheet is coated with the sodium aluminate solution.
- the sheet is passed through an electrically heated drying oven 32 maintained preferably at about 250 F. to 300 F.
- the heating furnace is, of course, of sufficient length and the temperature is sutficiently high so that the sodium aluminate coating will dry as it passes therethrough.
- the sheet supported by rollers 37 is passed into an electrically heated furnace 34 containing a reducing atmosphere in its chamber 36.
- a suitable sealing means 38 such as sealing rollers or an asbestos sheet, is provided in the furnace opening to retain the reducing atmosphere therein.
- the furnace '34 maintains the reducing atmosphere at a temperature preferably ranging from 1250 F. to 1450 F.
- the strip, guided by rollers 40 and 4-2 is dipped into molten zinc 46 contained in a cuucible or suitable container 48.
- the sheet is then guided downwardly by means of rollers 50 and 52, and thence into a tank 54 containing a water rinse 56 containing a suitable rust inhibitor such as sodium dichromate.
- the sheet is passed beneath a roller 58 and over rotary bristle brush 60 positioned adjacent the sodium aluminate coated surface of the sheet and rotating in a clock-wise direction.
- the brushing action together with the water rinse is effective in removing the aluminate coating from the sheet so as to provide a clean, zinc-free surface.
- the sheet is passed through a drying oven 62 which includes hot air blast nozzles 64 for the purpose of drying the sheet.
- the sheet is coiled on a roller 66.
- the various components of the apparatus for elfecting the continuous method described are of sufiicient length and of suitable design to effect the various steps in the process previously outlined.
- the various guide roller mechanisms, including the rollers 37, 40 and 42 are preferably of suitable design so as to grip the sheet at the edges thereof so as not to remove or destroy significant amounts of the alkali metal aluminate coating from the sheet as .it passes from the alkali metal aluminate container 28 and through the zinc dip bath 46.
- power may be applied to other rollers to efficiently move the sheet through the apparatus.
- the invention has been described in terms of galvanizing using a zinc bath, it is to be understood that the invention comprehends the addition of small amounts of aluminum to the molten zinc for the purpose of suppressing iron-zinc compound formations and the addition of small amounts of other metals such as lead, antimony, cadmium and tin used either singly or in various combinations for the purpose of improving the quality of the zinc coating.
- a process for galvanizing a portion only of a ferrous metal article comprising applying an alkali metal aluminate solution to the portion of the article which is not to be galvanized, drying said coating, surrounding said article by a reducing atmosphere and subjecting said article to heat in a temperature range of from about 1250 F. to 1450 F. while surrounded by said reducing atmosphere for a time suflicient to reduce the oxides on said ferrous metal, and dipping said article in a galvanizing bath while still under said reducing atmosphere.
- a process for galvanizing a portion only of the ferrous metal article comprising applying an alkali metal aluminate solution containing a small but effective amount of a wetting agent to the portion of the article which is not to be galvanized, drying said coating by subjecting said article to heat in a temperature range of from 250 F. to 700 F., surrounding said article by a reducing atmosphere and subjecting said article to heat in a temperature range of from about 1250 F. to 1450 F. while surrounded by said reducing atmosphere for a time sufiicient to reduce the oxides on said ferrous metal, and dipping said article in a galvanizing bath while still under said reducing atmosphere.
- a process for galvanizing a portion only of a ferrous metal article comprising cleaning said article, applying a sodium aluminate solution containing a small but effective amount of a non-ionic wetting agent to the portion of the article which is not to be galvanized, drying said coating by subjecting the same to heat at a temperature range from 250 F. to 700 F., surrounding said article by a reducing atmosphere and subjecting said article to heat at a temperature range of from about 1250 F. to 1450 F. While in said reducing atmosphere for a time sufficient to reduce the oxides on said ferrous metal, dipping said article in a galvanizing bath while under said reducing atmosphere,
- a process for galvanizing one side only of a sheet metal article comprising applying an aqueous alkali aluminate solution containing a small but effective amount of a wetting agent to the side of said sheet which is not to be galvanized, drying said coating by subjecting said sheet to heat in a temperature range from 250 F. to 700 F., surrounding said sheet by a reducing atmosphere and subjecting said sheet to heat in a temperature range of from about 1250 F. to 1450 F. while surrounded by said reducing atmosphere for a time sufiicient to reduce the oxides on said sheet, dipping said article in a galvanizing bath while still under said reducing atmosphere and thereafter removing said alkali metal aluminate coating.
- a process for galvanizing a ferrous metal article comprising applying an aqueous solution containing from about 5 to 20% of an alkali metal aluminate and a small but effective amount of a Wetting agent to the portion of said article which is not to be galvanized, drying said coating by subjecting said article to heat in a temperature range of from 250 F. to 300 F., surrounding said article by a reducing atmosphere and subjecting the article to heat in a temperature range of from about 1250 F. to 1450 F.
- a process for galvanizing one side only of a sheet steel article comprising cleaning said article, applying an aqueous solution containing about 20% of sodium aluminate and about 0.3% of a non-ionic Wetting agent, drying said coating by subjecting said article to heat in a temperature range of from about 250 F. to 300 F surrounding said article in a reducing atmosphere and heating the article within a temperature range of about 1250 F. to 1450 F. while slnrounded by said atmosphere for a time sufficient to reduce the oxides on said steel article, dipping said article in a galvanizing bath while under said reducing atmosphere and removing said sodium aluminate coating by brushing and a water rinse.
- a process for galvanizing a portion only of a ferrous metal article comprising applying an alkali metal aluminate solution to the portion of the article which is not to be galvanized, drying said coating, surrounding said article by a reducing atmosphere and subjecting said article to heat at a temperature of at least 1250 F. while surrounded by said reducing atmosphere for a time sufficient to reduce the oxides on said ferrous metal, and dipping said article in a galvanizing bath while still under said reducing atmosphere.
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
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- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Coating With Molten Metal (AREA)
Description
1959 J. L. GREENE ETAL 2,894,850 METHOD OF GALVANIZING'FERROUS METAL STRIP fiooooo k y oooooob United States Patent Birmingham, Mich, assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application May '14, 1958, Serial No. 735,316 7 Claims. (Cl. 117-55) This invention relates to a method of coating a base metal with another molten metal and more particularly to a method of galvanizing ferrous metal strip or sheet material on one side only.
Galvanized sheet metal is conventionally used in applications where the metal must necessarily be exposed to the corrosive effects of the elements and the like. It has been considered for use in automobile body construction to improve corrosion resistance, particularly on the interior surfaces of the body where rusting is generally most severe. However, commercial galvanized sheet, which is zinc coated on both sides, has never been generally accepted for automobile body construction on a commercial basis because of complications arising from the adherence of zinc to the electrode tips in the process of resistance welding the galvanized parts together. Moreover, the surface quality of galvanized sheet for exterior body surfaces is generally inferior to bare sheet steel.
For these reasons it is desirable to construct critical body components of galvanized sheet steel which is zinc coated on one side only, wherein the zinc coated surface is provided on the interior surfaces. This construction provides protective qualities on the interior surfaces where it is most needed and leaves the exterior surfaces uncoated for maximum weldability and surface finishing. These exterior uncoated surfaces are ultimately protected by a conventional painting treatment.
It is the basic object of this invention toprovide a method for galvanizing ferrous metal sheet or strip material on one side thereof only and leave the opposite surface free of the zinc coating and in a clean condition for optimum weldability and surface finishing.
It is a further object of this invention to provide a method of galvanizing sheet ferrous material on one side only which may be utilized in connection with galvanizing processes currently in commercial use. These and other objects are accomplished by a process including the steps of first cleaning or degreasing the sheet material by any well-known manner; coating one side of the sheet with an alkali metal aluminate solution, preferably containing small quantities of a suitable nonionic wetting agent which will not dissociate in a strongly alkaline solution; drying the alkali metal aluminate coated sheet; subjecting the dried sheet to a reducing atmosphere at temperatures ranging from about 1250 F. to l'450 F.; then dipping the sheet into molten zinc while still protected by the reducing atmosphere; and, finally, removing the sheet from the molten zinc, cooling it and removing the alkali metal aluminate coating by brushing or other suitable means.
Other objects and advantages of this invention will more fully appear from the following detailed description of a preferred embodiment of the invention, reference being made to the accompanying drawing which shows a schematic view of one form of apparatus suitable for carrying out the invention.
Incarrying out the basic aspects of the invention a steel sheet is first cleaned by dipping it in a cleaning bath containing a suitable detergent. Any well-known degreasingor cleaning method, such as by means of an electrolytic caustic solution or vapor degreasing, may be used. After the sheet has been suitably cleaned, one side thereof is coated with an aqueous alkali metal aluminate solution, preferably containing small quantities of a suitable wetting agent. An alkali metal aluminate coating of a thickness of .001 to .002 inch has been found satisfactory. The solution may be suitably applied by brushing. However, other methods of application, such as spraying or rolling may also be used. A preferred solution for this purpose is an aqueous solution containing about 20% sodium aluminate (NaAlO and about 0.3%
'of a wetting agent in the form of polyoxyethylene sorbitan monolaurate.
Although a 20% sodium aluminate solution represents a preferred concentration, sodium aluminate solutions as low as 5% may be used. Solutions below 5% are undesirable, since below this concentration the sodium aluminate tends to dissociate to sodium hydroxide and precipitated aluminum oxide with a result that these materials would be undesirably applied to the steel sheet. Higher concentrations of the sodium aluminate are also suitable, such higher concentrations being limited by the saturation characteristics of the sodium aluminate. Other alkali metal aluminates may also be used in place of the sodium aluminate as well as mixtures of alkali metal aluminates. Sodium and potassium aluminates are preferred because of their availability and high water solubility. Lithium aluminate is less desirable because of its low solubility in water while other alkali metal aluminates, such as rubidium and cesium aluminate are of limited use, as a practical matter, due to the scarcity and relatively high cost of these alkali metals.
In general it has been found that any of the wetting agents of the non-ionic type which are not subject to dissociation in strong alkaline solutions are suitable. Specific examples of wetting agents which have been successfully used include sorbitan mohooleate and mixtures of polyethylene oxide and polypropylene oxide. The Wetting agent is preferably presentin small but effective amounts, such as will permit an ethcient application of the alkali metal aluminate solution to the cleaned sheet metal.
After the alkali metal aluminate solution is applied to one side of the steel sheet, the sheet is preferably subjected to heat at temperatures ranging from 250 F. to 300 F. for a time sufficient to cause the sodium aluminate coating to dry. It has been found that drying temperatures up to 700 F. may also be used in the drying step whereby a very rapid drying may be accomplished. Experimental tests have indicated that the sodium aluminate coating, dried and baked at 600 F. to 700 F., involves an oxidation of the steel beneath the sodium aluminate coating but that this oxide is reduced so as to' provide a clean steel sheet in a subsequent reduction process, as will be hereinafter described.
After the sodium aluminate coating has been dried as described, the sheet is then placed in a reducing atmosphere heated to about 1400 F. for about 5 minutes or a time sufficient to remove all oxides from the metal. Reducing temperatures ranging from 1250 F. to 1450 F. may be satisfactorily used with an appropriate adjust ment in time. A reducing atmosphere of hydrogen having a dew point of F. has been found highly satisfactory for the purpose. Another suitable reducing atmosphere includes typically 12.5% hydrogen, 10.5% carbon monoxide, 5.0% carbon dioxide, 0.5% methane, 0.8% water, and 70.7% nitrogen. Another suitable re ducing atmosphere which may be used is cracked ammonia having a dew point of about 80 F.
After the sheet metal has been suitably exposed to the reducing atmosphere so as to fully remove any oxidized surface thereon and While still under the protective reducing atmosphere, it is dipped for about 5 to 30 seconds into molten zinc maintained at about 850 F. 'After the dipping step the sheet is permitted to cool and the coating to solidify by guiding it a sufficient distance in the atmosphere. The sodium aluminate coating is removed by a simple water rinse and brushing operation. It is to be understood that an important aspect of this invention resides in the use of the alkali metal aluminate solution which will remain adhered to the metal sheet during the galvanizing process, prevent the adherence of the zinc to the aluminate coated portions of the sheet metal and be readily removed by a simple operation such as brushing so as to provide a clean ferrous metal surface which is readily amendable to Welding operations and the reception of surface coating such as paint and the like. No other material has been found which will prevent the adherence of zinc and yet be readily removed after being subjected to the reducing heat treatment of 1250 F. or more.
The process as described above, as is readily apparent, may be conducted on a batch basis. However, the process may be readily adaptable to operation on a continuous basis as is illustrated in the drawing. Sheet -metal or strip is provided in the form of a roll mounted on a suitable rotatable supporting mechanism 12. In accordance with the process of the invention, the sheet is guided by suitable rollers 14, 16, 18 and 20, and continuously passed into and out of a cleaning bath 22 contained in tank 24. The tank 24 is, of course, suffi- -ciently large to permit the sheet metal to be adequately cleaned as it passes through. Thereafter the sheet is passed over a roller 26 which is partially submerged in a sodium aluminate solution 28 contained in a tank 30, whereby the underside of the sheet is coated with the sodium aluminate solution. Thereafter the sheet is passed through an electrically heated drying oven 32 maintained preferably at about 250 F. to 300 F. The heating furnace is, of course, of sufficient length and the temperature is sutficiently high so that the sodium aluminate coating will dry as it passes therethrough.
After leaving the heating oven 32, the sheet supported by rollers 37 is passed into an electrically heated furnace 34 containing a reducing atmosphere in its chamber 36. A suitable sealing means 38, such as sealing rollers or an asbestos sheet, is provided in the furnace opening to retain the reducing atmosphere therein. The furnace '34 maintains the reducing atmosphere at a temperature preferably ranging from 1250 F. to 1450 F. After leaving the reducing furnace 34, the strip, guided by rollers 40 and 4-2, is dipped into molten zinc 46 contained in a cuucible or suitable container 48. The sheet is then guided downwardly by means of rollers 50 and 52, and thence into a tank 54 containing a water rinse 56 containing a suitable rust inhibitor such as sodium dichromate. Within the Water rinse, the sheet is passed beneath a roller 58 and over rotary bristle brush 60 positioned adjacent the sodium aluminate coated surface of the sheet and rotating in a clock-wise direction. The brushing action together with the water rinse is effective in removing the aluminate coating from the sheet so as to provide a clean, zinc-free surface. Finally, the sheet is passed through a drying oven 62 which includes hot air blast nozzles 64 for the purpose of drying the sheet. Finally, the sheet is coiled on a roller 66.
It is to be understood that the various components of the apparatus for elfecting the continuous method described are of sufiicient length and of suitable design to effect the various steps in the process previously outlined. The various guide roller mechanisms, including the rollers 37, 40 and 42 are preferably of suitable design so as to grip the sheet at the edges thereof so as not to remove or destroy significant amounts of the alkali metal aluminate coating from the sheet as .it passes from the alkali metal aluminate container 28 and through the zinc dip bath 46. In general, it is only necessary to apply power to the roller 66 to draw the sheet 10 through the apparatus. However, power may be applied to other rollers to efficiently move the sheet through the apparatus.
Although the invention has been described in terms of galvanizing using a zinc bath, it is to be understood that the invention comprehends the addition of small amounts of aluminum to the molten zinc for the purpose of suppressing iron-zinc compound formations and the addition of small amounts of other metals such as lead, antimony, cadmium and tin used either singly or in various combinations for the purpose of improving the quality of the zinc coating.
While this invention has been described with reference to certain preferred embodiments and conditions, it will be understood that the invention is not limited thereby and numerous changes and modifications will be apparent to those skilled in the art without departing from the spirit and principles of the invention.
We claim:
1. A process for galvanizing a portion only of a ferrous metal article, the steps comprising applying an alkali metal aluminate solution to the portion of the article which is not to be galvanized, drying said coating, surrounding said article by a reducing atmosphere and subjecting said article to heat in a temperature range of from about 1250 F. to 1450 F. while surrounded by said reducing atmosphere for a time suflicient to reduce the oxides on said ferrous metal, and dipping said article in a galvanizing bath while still under said reducing atmosphere.
2. A process for galvanizing a portion only of the ferrous metal article, the steps comprising applying an alkali metal aluminate solution containing a small but effective amount of a wetting agent to the portion of the article which is not to be galvanized, drying said coating by subjecting said article to heat in a temperature range of from 250 F. to 700 F., surrounding said article by a reducing atmosphere and subjecting said article to heat in a temperature range of from about 1250 F. to 1450 F. while surrounded by said reducing atmosphere for a time sufiicient to reduce the oxides on said ferrous metal, and dipping said article in a galvanizing bath while still under said reducing atmosphere.
3. A process for galvanizing a portion only of a ferrous metal article, the steps comprising cleaning said article, applying a sodium aluminate solution containing a small but effective amount of a non-ionic wetting agent to the portion of the article which is not to be galvanized, drying said coating by subjecting the same to heat at a temperature range from 250 F. to 700 F., surrounding said article by a reducing atmosphere and subjecting said article to heat at a temperature range of from about 1250 F. to 1450 F. While in said reducing atmosphere for a time sufficient to reduce the oxides on said ferrous metal, dipping said article in a galvanizing bath while under said reducing atmosphere,
and removing the soditun aluminate solution.
4. A process for galvanizing one side only of a sheet metal article, the steps comprising applying an aqueous alkali aluminate solution containing a small but effective amount of a wetting agent to the side of said sheet which is not to be galvanized, drying said coating by subjecting said sheet to heat in a temperature range from 250 F. to 700 F., surrounding said sheet by a reducing atmosphere and subjecting said sheet to heat in a temperature range of from about 1250 F. to 1450 F. while surrounded by said reducing atmosphere for a time sufiicient to reduce the oxides on said sheet, dipping said article in a galvanizing bath while still under said reducing atmosphere and thereafter removing said alkali metal aluminate coating.
5. A process for galvanizing a ferrous metal article, the steps comprising applying an aqueous solution containing from about 5 to 20% of an alkali metal aluminate and a small but effective amount of a Wetting agent to the portion of said article which is not to be galvanized, drying said coating by subjecting said article to heat in a temperature range of from 250 F. to 300 F., surrounding said article by a reducing atmosphere and subjecting the article to heat in a temperature range of from about 1250 F. to 1450 F. while surrounded by said reducing atmosphere for a time sufiicient to reduce the oxides on said ferrous metal, dipping said article in a galvanizing bath While still under said reducing atmosphere and removing alkali metal silicate coating by means of a brush and a Water rinse.
6. A process for galvanizing one side only of a sheet steel article, the steps comprising cleaning said article, applying an aqueous solution containing about 20% of sodium aluminate and about 0.3% of a non-ionic Wetting agent, drying said coating by subjecting said article to heat in a temperature range of from about 250 F. to 300 F surrounding said article in a reducing atmosphere and heating the article within a temperature range of about 1250 F. to 1450 F. while slnrounded by said atmosphere for a time sufficient to reduce the oxides on said steel article, dipping said article in a galvanizing bath while under said reducing atmosphere and removing said sodium aluminate coating by brushing and a water rinse.
7. A process for galvanizing a portion only of a ferrous metal article, the steps comprising applying an alkali metal aluminate solution to the portion of the article which is not to be galvanized, drying said coating, surrounding said article by a reducing atmosphere and subjecting said article to heat at a temperature of at least 1250 F. while surrounded by said reducing atmosphere for a time sufficient to reduce the oxides on said ferrous metal, and dipping said article in a galvanizing bath while still under said reducing atmosphere.
No references cited.
Claims (1)
1. A PROCESS FOR GALVANIZING A PORTION ONLY OF A FERROUS MEWTAL ARTICLE, THE STEPS COMPRISING APPLYING AN ALKALI METAL ALUMINATE SOLUTION TO THE PORTION OF THE ARTICLE WHICH IS NOT TO BE GALVANIZED, DRYING SAID COATING, SURROUNDING SAID ARTICLE BY A REDUCING ATMOSPHERE AND SUBJECTING SAID ARTICLE TO HEAT IN A TEMPERATURE RANGE OF FROM ABOUT 1250* F. TO 1450* F. WHILE SURROUNDED BY SAID REDUCING ATMOSPHERE FOR A TIME SUFFICIENT TO REDUCE THE OXIDES ON SAID FERROUS METAL, AND DIPPING SAID ARTICLE IN A GALVANIZIONG BATH WHILE STILL UNDER SAID REDUCING ATMOSPHERE.
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US735316A US2894850A (en) | 1958-05-14 | 1958-05-14 | Method of galvanizing ferrous metal strip |
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US735316A US2894850A (en) | 1958-05-14 | 1958-05-14 | Method of galvanizing ferrous metal strip |
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US2894850A true US2894850A (en) | 1959-07-14 |
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Cited By (18)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3089780A (en) * | 1961-05-04 | 1963-05-14 | United States Steel Corp | Method and composition for shielding steel from molten coating metal |
US3104993A (en) * | 1960-09-20 | 1963-09-24 | Inland Steel Co | Galvanizing process |
US3121019A (en) * | 1961-02-20 | 1964-02-11 | Selas Corp Of America | Galvanizing one side of a strip of metal |
US3145468A (en) * | 1961-10-05 | 1964-08-25 | Inland Steel Co | Sheet marking method |
US3149987A (en) * | 1961-12-11 | 1964-09-22 | Bethlehem Steel Corp | Method of coating metals |
US3177085A (en) * | 1960-07-27 | 1965-04-06 | Nalco Chemical Co | Silica sol-masking in galvanizing process |
US3181963A (en) * | 1960-11-08 | 1965-05-04 | Wheeling Steel Corp | Alkali metal borate masking in galvanizing process |
US3260577A (en) * | 1961-12-20 | 1966-07-12 | Nat Steel Corp | Coated product and its manufacture |
DE1236299B (en) * | 1961-05-04 | 1967-03-09 | United States Steel Corp | Process for one-sided coating of sheet metal and strips made of steel with metal, preferably zinc, by immersion in a molten metal bath |
DE1246351B (en) * | 1960-11-08 | 1967-08-03 | Wheeling Steel Corp | Method for one-sided or partial hot-dip galvanizing of objects made of ferrous metals, especially strips |
US3398010A (en) * | 1964-08-17 | 1968-08-20 | United States Steel Corp | Masking composition for galvanized metal |
US3826227A (en) * | 1972-12-13 | 1974-07-30 | D T & G Ltd | Tinning machine |
US3928657A (en) * | 1971-04-15 | 1975-12-23 | British Steel Corp | Strip shape correction on galvanising line |
US3962501A (en) * | 1972-12-15 | 1976-06-08 | Nippon Steel Corporation | Method for coating of corrosion-resistant molten alloy |
US4047977A (en) * | 1972-05-04 | 1977-09-13 | Nippon Steel Corporation | Method of continuous galvanizing steel strip on partial or one side |
US4177303A (en) * | 1977-04-22 | 1979-12-04 | Dominion Foundries And Steel, Limited | Method of galvanizing a portion only of a ferrous metal article |
US4264652A (en) * | 1978-09-13 | 1981-04-28 | Desire Danese | Method for locally galvanizing a piece of metal |
US4330574A (en) * | 1979-04-16 | 1982-05-18 | Armco Inc. | Finishing method for conventional hot dip coating of a ferrous base metal strip with a molten coating metal |
-
1958
- 1958-05-14 US US735316A patent/US2894850A/en not_active Expired - Lifetime
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Cited By (18)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3177085A (en) * | 1960-07-27 | 1965-04-06 | Nalco Chemical Co | Silica sol-masking in galvanizing process |
US3104993A (en) * | 1960-09-20 | 1963-09-24 | Inland Steel Co | Galvanizing process |
US3181963A (en) * | 1960-11-08 | 1965-05-04 | Wheeling Steel Corp | Alkali metal borate masking in galvanizing process |
DE1246351B (en) * | 1960-11-08 | 1967-08-03 | Wheeling Steel Corp | Method for one-sided or partial hot-dip galvanizing of objects made of ferrous metals, especially strips |
US3121019A (en) * | 1961-02-20 | 1964-02-11 | Selas Corp Of America | Galvanizing one side of a strip of metal |
DE1236299B (en) * | 1961-05-04 | 1967-03-09 | United States Steel Corp | Process for one-sided coating of sheet metal and strips made of steel with metal, preferably zinc, by immersion in a molten metal bath |
US3089780A (en) * | 1961-05-04 | 1963-05-14 | United States Steel Corp | Method and composition for shielding steel from molten coating metal |
US3145468A (en) * | 1961-10-05 | 1964-08-25 | Inland Steel Co | Sheet marking method |
US3149987A (en) * | 1961-12-11 | 1964-09-22 | Bethlehem Steel Corp | Method of coating metals |
US3260577A (en) * | 1961-12-20 | 1966-07-12 | Nat Steel Corp | Coated product and its manufacture |
US3398010A (en) * | 1964-08-17 | 1968-08-20 | United States Steel Corp | Masking composition for galvanized metal |
US3928657A (en) * | 1971-04-15 | 1975-12-23 | British Steel Corp | Strip shape correction on galvanising line |
US4047977A (en) * | 1972-05-04 | 1977-09-13 | Nippon Steel Corporation | Method of continuous galvanizing steel strip on partial or one side |
US3826227A (en) * | 1972-12-13 | 1974-07-30 | D T & G Ltd | Tinning machine |
US3962501A (en) * | 1972-12-15 | 1976-06-08 | Nippon Steel Corporation | Method for coating of corrosion-resistant molten alloy |
US4177303A (en) * | 1977-04-22 | 1979-12-04 | Dominion Foundries And Steel, Limited | Method of galvanizing a portion only of a ferrous metal article |
US4264652A (en) * | 1978-09-13 | 1981-04-28 | Desire Danese | Method for locally galvanizing a piece of metal |
US4330574A (en) * | 1979-04-16 | 1982-05-18 | Armco Inc. | Finishing method for conventional hot dip coating of a ferrous base metal strip with a molten coating metal |
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