US2856275A - Chemical treatment of refractory metal surfaces - Google Patents
Chemical treatment of refractory metal surfaces Download PDFInfo
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- US2856275A US2856275A US623316A US62331656A US2856275A US 2856275 A US2856275 A US 2856275A US 623316 A US623316 A US 623316A US 62331656 A US62331656 A US 62331656A US 2856275 A US2856275 A US 2856275A
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- 238000011282 treatment Methods 0.000 title description 19
- 239000003870 refractory metal Substances 0.000 title description 3
- 239000000126 substance Substances 0.000 title description 2
- 238000005554 pickling Methods 0.000 claims description 35
- 239000000203 mixture Substances 0.000 claims description 26
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims description 19
- 229910052726 zirconium Inorganic materials 0.000 claims description 19
- 239000002253 acid Substances 0.000 claims description 18
- 238000000034 method Methods 0.000 claims description 15
- 239000003795 chemical substances by application Substances 0.000 claims description 13
- 230000008569 process Effects 0.000 claims description 11
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 10
- 229910017604 nitric acid Inorganic materials 0.000 claims description 10
- 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 claims description 8
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims description 8
- 229910052700 potassium Inorganic materials 0.000 claims description 8
- 229910052708 sodium Inorganic materials 0.000 claims description 8
- 239000011734 sodium Substances 0.000 claims description 8
- 239000011591 potassium Substances 0.000 claims description 7
- 239000001257 hydrogen Substances 0.000 claims description 4
- 229910052739 hydrogen Inorganic materials 0.000 claims description 4
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 claims description 3
- XTEGARKTQYYJKE-UHFFFAOYSA-M Chlorate Chemical compound [O-]Cl(=O)=O XTEGARKTQYYJKE-UHFFFAOYSA-M 0.000 claims description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 3
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical class [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 3
- 230000002378 acidificating effect Effects 0.000 claims description 3
- WQYVRQLZKVEZGA-UHFFFAOYSA-N hypochlorite Chemical compound Cl[O-] WQYVRQLZKVEZGA-UHFFFAOYSA-N 0.000 claims description 3
- 150000002978 peroxides Chemical class 0.000 claims description 3
- 239000007788 liquid Substances 0.000 claims description 2
- 238000000060 site-specific infrared dichroism spectroscopy Methods 0.000 claims 1
- 239000007800 oxidant agent Substances 0.000 description 35
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 34
- 229910052751 metal Inorganic materials 0.000 description 29
- 239000002184 metal Substances 0.000 description 29
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 25
- 229910052719 titanium Inorganic materials 0.000 description 25
- 239000010936 titanium Substances 0.000 description 25
- 230000004580 weight loss Effects 0.000 description 24
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 23
- BZSXEZOLBIJVQK-UHFFFAOYSA-N 2-methylsulfonylbenzoic acid Chemical compound CS(=O)(=O)C1=CC=CC=C1C(O)=O BZSXEZOLBIJVQK-UHFFFAOYSA-N 0.000 description 17
- 239000011780 sodium chloride Substances 0.000 description 17
- 238000005282 brightening Methods 0.000 description 14
- 230000009467 reduction Effects 0.000 description 14
- 230000000694 effects Effects 0.000 description 11
- 239000000243 solution Substances 0.000 description 11
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 10
- 238000012360 testing method Methods 0.000 description 8
- 150000002739 metals Chemical class 0.000 description 7
- 230000001590 oxidative effect Effects 0.000 description 6
- 150000007513 acids Chemical class 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 4
- 239000005708 Sodium hypochlorite Substances 0.000 description 3
- 239000000956 alloy Substances 0.000 description 3
- 229910045601 alloy Inorganic materials 0.000 description 3
- 239000002932 luster Substances 0.000 description 3
- 238000005498 polishing Methods 0.000 description 3
- SUKJFIGYRHOWBL-UHFFFAOYSA-N sodium hypochlorite Chemical compound [Na+].Cl[O-] SUKJFIGYRHOWBL-UHFFFAOYSA-N 0.000 description 3
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical class [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 239000011260 aqueous acid Substances 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 239000000460 chlorine Substances 0.000 description 2
- 150000001805 chlorine compounds Chemical class 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 159000000000 sodium salts Chemical class 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 238000005303 weighing Methods 0.000 description 2
- 101100165177 Caenorhabditis elegans bath-15 gene Proteins 0.000 description 1
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical class [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000012042 active reagent Substances 0.000 description 1
- 235000019270 ammonium chloride Nutrition 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 150000003841 chloride salts Chemical class 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000003467 diminishing effect Effects 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 150000004767 nitrides Chemical class 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
- 235000021110 pickles Nutrition 0.000 description 1
- 239000001103 potassium chloride Substances 0.000 description 1
- 235000011164 potassium chloride Nutrition 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000001117 sulphuric acid Substances 0.000 description 1
- 235000011149 sulphuric acid Nutrition 0.000 description 1
- 238000010301 surface-oxidation reaction Methods 0.000 description 1
- 238000012956 testing procedure Methods 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- -1 zirconium metals Chemical class 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
-
- 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
- C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
- C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
- C23G1/10—Other heavy metals
- C23G1/106—Other heavy metals refractory metals
Description
United States Patent CHEMICAL TREATMENT OF REFRACTORY METAL SURFACES George F. Otto, Oreland, Pa, assignor to Amchem Products, a corporation of Delaware No Drawing. Application November 20, 1%56 Serial No. 623,316
6 Claims. (Cl. 41-42) This invention relates to the pickling and brightening of certain refractory metals. More specifically, it has to do with the use of acidic pickling media in conjunction with oxidizing. agents in the treatment titanium and zirconium metals and their alloys.
Objects composed of zirconium or titanium, or of alloys in which these metals predominate, present unusual problems insofar as providing them with bright, clear, finished surfaces is concerned. This is because these metals, particularly at elevated temperatures, have a very strong afiinity for oxygen, hydrogen, nitrogen, and other scale-forming elements. Consequently, contact between these metals and gases of the type referred to, either during preliminary handling of the metals or in the final fabrication of them, often results in the formation of oxide films, or of surface scale, either of which will blemish the finished surface. Oxide and nitride scales are particularly troublesome, and the presence of such scale not infrequently renders the products unsuitable for the purposes for which they had been originally intended.
Surface scale and films of the type referred to adhere very tenaciously to both titanium and zirconium, and for thisreason, it has frequently been found that conventional pickling processes, making use of sulphuric acid or hydrochloric acid, for example, have been ineffective to remedy the difliculty. In order to pickle titanium and zirconium successfully, it has become customary to resort to the use of aqueous solutions containing a mixture of hydrofluoric acid and nitric acid, although the use of hydrofluoric acid alone has been proposed.
Generally speaking, the pickling baths most commonly used for treatment of these metals consist of a mixture of hydrofluoric acid and nitric acid in water, the hydrofluoric' acid representing froml% to 6% of the bath, by weight, and the nitric acid from 1 to 50%.
Hydrofluoric acid alone, in concentrations ranging up to 60% is quite capable of removing any scale or film likely to be encountered on the surface of titanium or zirconium objects, but it attacks the basis metal so actively that most metal finishers prefer to combine it with the slower-acting nitric acid.
But even when the acid content of the pickling bath consists mainly of nitric acid, with only a small proportion of hydrofluoric acid, the activity of the pickling solution is so great as to entail an extensive and costly loss of the basis metal. Furthermore, pickling these metals with such baths frequently leaves the surface in a seriously pitted condition.
An object of this invention is to provide an acid pickling bath which will satisfactorily remove surface contaminants from articles made of zirconium or titanium or alloys in which these metals predominate, without causing an objectionable loss of the basis metal. A concomitant object of the invention is the provision of pickling solutions which, in use, will cause little or no pitting of the pickled surface. Another object of the invention is the provision of treating solutions which are capable ting a very pronounced brightening of Zirconium ice and titanium surfaces to which they have been applied. Other objects and advantages of the invention will be apparent as this detailed description proceeds.
A fundamental concept of the present invention is the discovery that if one adds an oxidizing agent to a pickling bath for titanium and zirconium, which bath contains a mixture of nitric acid and hydrofluoric acid, the activity of the pickling bath with respect to surface contaimi nants, such as film and scale, is not substantially reduced, but there is nevertheless a significant lessening of the rate of attack of the acid on the basis metal, or, alternatively, or coordinately, a marked enhancement in the brightening effect of the bath upon the surfaces treated, and substantial elimination of surface pitting.
As oxidizing agents, I may use sodium salts of chlorine,
such as sodium chloride, sodium chlorate and sodium hypochlorite. Alternatively, I may use the corresponding chloride salts of potassium, or ammonium chloride. Still further, hydrogen peroxide may be used. Mixtures of compatible oxidizing agents are highly effective, the preferred composition being one which contains sodium chloride and sodium chlorate in equal proportions.
All of these compounds have the characteristic of serving as oxidizing agents for the basis metal, in the sense that they will cause the metal to manifest a higher valence.
Entirely apart from the problem of scale removal, the brightening of zirconium or titanium surfaces may be very effectively achieved by the combination of such oxidizing agents with the acids of the pickling bath. It has been discovered that, even at relatively low concentrations, the presence of such oxidizing agents in the composition uniformly results in the production of a more brilliant surface than is produced Without them, and often results in the production of a pickled surface having such a high degree of sheen as to completely eliminate the necessity of resorting to subsequent polishing operations.
As to the concentrations in which the oxidizing agents are used, it should first be pointed out that since one effect of these oxidizing agents is to inhibit the attack of the pickling acids on the basis metal, the presence of these agents tends to slow down the activity of the pickling bath. It is, therefore, necessary to increase the time allowed for the metal-treating operation as the proportion of oxidizing agent in the pickling bath is increased. Subject to this limitation, concentrations as low as 2 grams per liter, and as high as 50 grams per liter, fall within the limits of the commercially useful range. At concentrations below 2 grams per liter, the inhibiting effect is scarcely sufficient to be noticeable, except when the oxidizing material used is hydrogen peroxide, which gives good results at concentrations equivalent to as little as 1.5 grams per liter (weight/volume). Even at such low concentrations, however, a substantial brightening effect may be secured. At concentrations above 50 grams per liter, the process may be slowed down to such a degree as to appreach the point of diminishing returns. That is to say: the saving in basis metal. may be more than off-set by rising costs due to the increase in processing time required.
As a general rule, the amount of oxidizing agent present, in relation to the total weight of the solution, may desirably be varied in direct proportion to the amount of pickling acid which the bath contains. However, this is a factor which is strongly affected by time, temperature, the resistivity of the scale, and the degree of brightening desired. Under some circumstances, for example, it may be desirable to use a relatively low proportion of oxidizing agent even in a bath which contains a rather high concentration of picklingacid, and vice versa. Where the conditions under which an article was fabricated, for example, are such as to have resulted in the presence of relatively littlescale, and it is desired to perform the pickling and brightening operation at relatively high speed,
the acid concentration may be high and the oxidation agent concentration may be low. The reverse would be true where thin sections coated with refractory scale are to be treated. Here it is vital to keep the weight loss at a minimum, and yet remove the scale completely. Consequently, under these circumstances, the oxidizing agents should be used at higher levels of concentration than is normal, the acid, particularly the hydrofluoric acid, should be at low concentration, and the porcessing time should be increased.
It is easy to evaluate the effectiveness of the treatment in relation to the removal of surface scale and oxide film by simple visual examination, noting the brightness of the treated surface and the extent of surface pitting, if any.
In order to evaluate the effectiveness of the treatment in relation to reduction in Weight loss, the following testing procedure has been adopted as a standard: First, place several small test panels, known as coupons, of the metal to be treated in a pickling bath which contains nitric acid by weight and 2% hydrofluoric acid by weight of the total solution. Allow the coupons to remain in the bath for 30 seconds at room temperature, then remove them, wash with water, and dry. The purpose of this treatment is to ensurethat the surface of all coupons is uniformly and completely clean. After washing and drying, each coupon is individually weighed.
The next step in evaluating weight loss is to test a control. This is done by immersing one of thecoupons in a 20% nitric 2% hydrofluoric acid test bath at room temperaturefor exactly 60 seconds, and then rinsing, drying and re-weighing the control specimen. Weight loss attributable to the action of the pickling bath is measured in milligrams per square foot.
Another specimen, cleaned in the same way as the control, is immersed, after Weighing, in a pickling bath having exactly the same acid concentration, plus 2 grams per liter of the selected oxidizing agent. The coupon is permitted to remain in the bath for the same sixty-second interval at the same temperature, following which it is rinsed, dried and re-weighed.
The procedure is repeated, increasing each time the proportion of oxidizing agent present in the bath.
Table I, which follows, shows the results of three sets of tests conducted at different times, but here grouped together to afford a comparison of the results following use of ditferent oxidizing materials, namely, sodium chloride, sodium chlorate, and a mixture of equal parts of sodium chloride and sodium chlorate, in pickling baths applied to coupons of titanium metal.
TABLE I [Treatment of titanium metal for 60 seconds at room temperature in aqueous bath containing 20% HNO; and 2% HF] All coupons in any one column were cut from the same sheet, but the coupons in each series were cut from different sheets. This accounts for the difference in weight loss of the respectively difierent control coupons.
It Will be noted that with sodium chloride a concentration of 2 grams per liter is insufficient to produce any substantial reduction in weight loss. Indeed, at this concentration, there would seem to be some slight increase in metal loss, rather than decrease. But the F loss is fairly substantial even at 2 effect in brightening the surface is marked, even at this low concentration, as compared to the degree of brilliance produced by the same pickling bath in the absence of any oxidizing agent. When the concentration of sodium chloride is increased to 4 grams per liter, there is an appreciable reduction in the weight loss, and at 8 grams per liter, the reduction in weight loss is almost out in half, as compared to that incurred where no oxidizing agent is used. With the oxidizing agent at concentrations in the neighborhood of 15 g. p. 1., so high a degree of surface brilliance is secured in 60 seconds as to obviate the need for further polishing, and pitting of the surface does not occur.
When sodium chlorate is used, the reduction in weight grams per liter concentration, and at 50 grams per liter, the weight loss has been reduced by over However, it should be mentioned that the brilliance of the surface produced in an immersion time of only 60 seconds was very much less where the higher concentration of oxidizing agent was employed than it was where lower concentrations were used. In other words, the time required for attaining a desired degree of brilliance in the final surface would have to be very substantially increased in a pickling bath which contained 50 grams per liter of sodium chlorate.
This observation explains why it is preferable to use mixtures of oxidizing agents, as shown in the third column of Table I, where the oxidizing material was a mixture of equal parts of sodium chloride and sodium chlorate. When this mixture is used, the weight loss incurred in treating titanium is not reduced as significantly, at any given concentration, as when either sodium chloride or sodium chlorate is used alone. But for reasons not yet entirely clear, the effect of using a mixture of these two salts is to make it possible to produce the same degree of brightening of the final finish in a substantially shorter time, or, as related to Table I, to produce a much more brilliant sheen in sixty seconds than can be produced by using the pickling acids alone, or by using these acids with either sodium chloride or sodium chlorate alone.
Considering all of the factors involved, our preferred procedure in treating titanium is to use a pickling bath which contains 20% of nitric acid and 2% hydrofluoric acid by weight in relation to the total weight of the bath, and to add to this bath 15 grams per liter of. a mixture of equal parts of sodium chloride and sodium chlorate. With a bath of this composition, complete scale removal and the desired degree of surface brightening can be attained in sixty seconds at room temperature, with a reduction in weight loss in the neighborhood of 40%, in a majority of cases.
In conducting the tests reported in Table I above, titanium metal was employed. Parallel tests, conducted in exactly the same way, but with the substitution of zirconium coupons in lieu of titanium, show the following results:
TABLE II aqueous bath containing 20% HNOa and 2% HF Weight Loss in Milligrams per Sq. Ft.
Grams per liter used NaOl NaOlOs NaCl+ NaOlOa All of the tests reported in Table II were conducted at the same time, using coupons cut from the same sheet. Consequently, the weight loss in each control specimen is the same.
Where zirconium is treated, the optimum balance between brilliance of finish and reduction in weight loss occurs when the concentration of oxidizing agent is at a higher level than is preferred where titanium is being treated. It will be seen from an examination of Table II that the reduction in weight loss becomes substantial when the oxidizing agent is present in concentrations ranging upwards from 30 grams per liter, whereas, in the treatment of titanium, the preferred value is grams per liter.
It will also be noted that in treating zirconium, a mixture of sodium chloride and sodium chlorate affords a greater reduction in weight loss at the lower levels of concentration than is afforded if either of these oxidizing agents is used alone. This is not the case in treating titanium.
Although it is true that the presence of the oxidizing agent in the treatment of zirconium does not effect an equivalent reduction in weight loss until the concentration of oxidizing agent is relatively higher than in the treatment of titanium, the effect of the oxidizing agents in brightening of the surface is much more strongly marked at low concentrations when zirconium is treated than is observed in the treatment of titanium. Whereas, in the treatment of titanium, maximum brilliance is not secured in 60 seconds until the concentration of oxidizing agent is in the neighborhood of 15 grams per liter, it has been found that nearly maximum brightening took place even at the lowest levels of concentration where the oxidizing agent in a pickling bath applied to zirconium consisted of a mixture of sodium chloride and sodium chlorate in equal proportions.
Consequently, where the purpose is primarily to brighten the surface of the finished article, and the article is made of zirconium metal, the preferred oxidizing agent is a mixture of equal parts of sodium chloride and sodium chlorate at a concentration of 4 grams per liter. This is also the preferred concentration where scale removal, in addition to surface brightening, is required, since it permits operation of the bath at the fastest possible rate, and yet produces a completely satisfactory degree of surface finishing. The reduction in metal loss is relatively slightabout 12.5%, but the sheen is sufficiently well developed as to require no further polishing treatments whatever in most cases where this mixture is used in the treatment of zirconium.
If procedures analogous to those employed in arriving at the values given in Table I and Table II are applied to the evaluation of other oxidizing agents, results which may fairly be regarded as comparable will be secured.
For example, the weight loss on coupons of titanium metal in a pickling bath containing the same mixture of pickling acids as was used in the tests reported in Table I and Table II and containing varying concentrations of sodium hypochlorite showed values of the following order of magnitude:
When sodium hypochlorite is present as the sole oxidizing agent in the pickling bath, in quantities approximating 15 grams per liter, the weight loss is reduced by 27.5% as compared to the control, and at this value, a high luster is imparted to the surface in 60 seconds of treatment.
At a concentration of 50 g. p. 1., the weight loss, as compared to the control was reduced by 63%, but the production of optimum brilliance required treatment for a longer time. Even at only 4% concentration of oxidizing agent, weight loss was reduced by 14%, and here the degree of surface brightening produced in sixty seconds was excellent.
Hydrogen peroxide is an especially desirable oxidizing agent for use in this process, since as little as 0.15%
(weight/volume) has been found to be effective as the oxidizing agent in pickling baths of the type discussed. It is, however, more costly than either of the sodium salts just mentioned, and is more difficult to handle (especially from the standpoint of deterioration during storage). Furthermore, it is a little difficult, particularly for relatively unskilled labor, to make certain that precisely the desired proportion of active reagent is employed, because hydrogen peroxide solutions are likely to undergo changes while standing with respect to the amount of available oxygen, as is well understood in this art.
Various combinations of oxidizing agents may be used, but experiments have indicated that the most advantageous treatment involves the use of a mixture of sodium chloride and sodium chlorate in equal proportions, taking into account all of the factors which should be considered in evaluating complete effectiveness, including, in addition to those previously mentioned, over-all total cost and ease of operation. It will immediately be apparent that both of these oxidizing agents are quite inexpensive from the standpoint of re-agent costs, and that they are freely soluble under the conditions of operation. Moreover, they not only eliminate pitting but also effect substantial reduction in weight loss due to acid attack upon the basis metal while at the same time producing a completely acceptable degree of surface luster in only sixty seconds of treating time.
It will be at once apparent that the number of permutations possible in utilizing the process of the present invention is very large. But the essential principle involved is nonetheless quite simple. For this reason, the data supplied above is intended to show how the effectiveness of any given permutation can be quickly and accurately determined, and is not intended to demonstrate the full range of possibilities.
The oxidizing materials previously referred to (viz., the chlorides of sodium, potassium and ammonium, the chlorates and hypochlorites of sodium and potassium, and peroxide of hydrogen) have all proved to be effective in attaining one or more of the desired objectives, namely, reduction in weight loss, increase in luster or sheen, and substantial reduction of pitting.
In conclusion, it may be said that a most striking aspect of the present invention is the concept of adding an oxidizing material of the type described to a pickling bath for the treatment of titanium or zirconium, which bath contains a mixture of nitric and hydrofluoric acids. This is regarded as a most implausible proposal, for the scale and film to be removed are themselves the products of surface oxidation. It is surprising indeed that the result of this procedure is not only to produce a clean and brilliant surface, free of oxide film and scale, but also to reduce the weight loss due to acid attack upon the basis metal, and to practically eliminate pitting of the surface.
I claim:
1. In the process of finishing the surfaces of articles composed at least in major part of a metal selected from the class which consists of titanium and zirconium by treating such surfaces with an acid pickling bath to re move oxide film and scale, the improvement which consists in adding to an aqueous pickling bath containing an acidic agent which consists of hydrofluoric acid in an amount equal to from 1% to 6% by weight of the solution mixed with nitric acid in an amount equal to from 10% to 50% by weight of the solution, a minor amount ranging from 0.15% to 5% 'by weight of the solution of an agent selected from the class which consists of the chlorides of sodium, potassium and ammonium; the chlorates and hypochlorites of sodium and potassium; peroxide of hydrogen; and mixtures of the same, and subjecting the article to be treated to contact with the liquid so prepared under time and temperature conditions sufficient to remove said scale and film.
2. A process as defined in claim 1, characterized in that said agent is hydrogen peroxide, which is present in an amount at least as great as 0.15 grams per 100 ml. of the solution. 3. A process as defined in claim 1, characterized in that the said agent consists of at least one chloride-containing salt of a metal selected from the class which comprises sodium and potassium.
4. A process as defined in claim 3, in which the said agent consists of a mixture of sodium'chloride and sodium chlorate, and is present in an amount at least as great as 2 grams per liter in the aqueous solution.
5. A process as defined in claim 3, in Whichthe said agent consists of a mixture of sodium chloride and sodium chlorate in substantially equal proportions, and in which the mixture constitutes approximately 1.5 by weight of the aqueous acid solution.
6. The process of claim 1, in which the surface treated consists essentially of titanium metal, and the said agent constitutes a mixture of sodium chloride and sodium chlorate, representing approximately 1.5% by weight of the aqueous acid bath.
References Cited in the file of this patent UNITED STATES PATENTS 2,154,455 Kepfer Apr. 18, 1939 2,154,469 Oplinger Apr. 18, 1939 2,283,170 Batcheller May 19, 1942 2,542,727 Theuerer Feb. 20, 1951 2,577,803 Pfann Dec. 11, 1951 2,606,960 Little Aug. 12, 1952 2,711,364 Beach June 21, 1955. 2,740,699 Koury Apr. 3, 1956
Claims (1)
1.IN THE PROCESS OF FINISHING THE SURFACE OF ARTICLES COMPOSED AT LEAST IN MAJOR PART OF A METAL SELECTED FROM THE CLASS WHICH CONSISTS OF TITANIU AND ZIRCONIUM BY TREATED SUCH SURFACES WITH AN ACID PICKLING BATH TO REMOVE OXIDE FILM AND SCALE, THE IMPRVEMENT WHICH CONSISTS IN ADDING TO AN AQUEOUS PICKLING BATH CONTAINING AN ACIDIC AGENT WHICH CONSISTS OF HYFROFLUORIC ACID IN AN AMOUNT EQUAL TO FORM 1% TO 6% BY WEIGHT OF SOLUTION MIXED WITH NITRIC ACID IN AN AMOUNT EQUAL TO FROM 10% TO 50% BY WEIGHT OF THE SOLUTION, A MINOR AMOUNT RANGING FROM 0.5% TO 5% BY WEIGHT OF THE SOLUTION OF AN AGENT SELECTED FROM THE CLASS WHICH CONSISTS OF THE CHLORIDES OF SODIUM, POTASSIUM AND AMMONIUM; THE CHLORATES AND HYPOCHLORITES OF SODIUM AND POTASSIUM; PEROXIDE OF HYDROGEN; AND MIXTURES OF THE SAME, AND SUBJECTING THE ARTICLE TO BE TREATED TO CONTACT WITH THE LIQUID SO PREPARED UNDER TIME AND TEMPERATURE CONDITIONS SUFFICIENT TO REMOVE SSID SCALE AND FILM.
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US623316A US2856275A (en) | 1956-11-20 | 1956-11-20 | Chemical treatment of refractory metal surfaces |
DEA27939A DE1101899B (en) | 1956-11-20 | 1957-09-19 | Acid, aqueous solution for descaling and glazing objects made of titanium, zircon and their alloys |
FR1184446D FR1184446A (en) | 1956-11-20 | 1957-10-16 | Improvements in the surface treatment of articles or objects in zirconium, titanium and their alloys |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US623316A US2856275A (en) | 1956-11-20 | 1956-11-20 | Chemical treatment of refractory metal surfaces |
Publications (1)
Publication Number | Publication Date |
---|---|
US2856275A true US2856275A (en) | 1958-10-14 |
Family
ID=24497601
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US623316A Expired - Lifetime US2856275A (en) | 1956-11-20 | 1956-11-20 | Chemical treatment of refractory metal surfaces |
Country Status (3)
Country | Link |
---|---|
US (1) | US2856275A (en) |
DE (1) | DE1101899B (en) |
FR (1) | FR1184446A (en) |
Cited By (19)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2977204A (en) * | 1959-08-14 | 1961-03-28 | Donald W Shannon | Method of improving corrosion resistance of zirconium |
US2981609A (en) * | 1956-11-20 | 1961-04-25 | United Aircraft Corp | Etching bath for titanium and its alloys and process of etching |
US3024095A (en) * | 1958-04-25 | 1962-03-06 | Nat Res Corp | Acid treatment of tantalum to remove surface irregularities |
US3082137A (en) * | 1958-12-03 | 1963-03-19 | Gen Motors Corp | Method and composition for etching titanium |
US3125474A (en) * | 1964-03-17 | Pickling zirconium and zirconium base alloys | ||
US3361674A (en) * | 1964-06-05 | 1968-01-02 | Bell Telephone Labor Inc | Copper etchant |
US3450575A (en) * | 1968-01-17 | 1969-06-17 | Alexander J Riscky | Method of repairing heat cracks on ferrous metal engines |
US3537895A (en) * | 1965-04-27 | 1970-11-03 | Lancy Lab | Copper and aluminum pickling |
US3905837A (en) * | 1972-03-31 | 1975-09-16 | Ppg Industries Inc | Method of treating titanium-containing structures |
US4754803A (en) * | 1987-02-02 | 1988-07-05 | Phelps Dodge Industries, Inc. | Manufacturing copper rod by casting, hot rolling and chemically shaving and pickling |
US4900398A (en) * | 1989-06-19 | 1990-02-13 | General Motors Corporation | Chemical milling of titanium |
US4946520A (en) * | 1987-02-02 | 1990-08-07 | Phelps Dodge Industries, Inc. | Copper rod manufactured by casting, hot rolling and chemically shaving and pickling |
US5051141A (en) * | 1990-03-30 | 1991-09-24 | Rem Chemicals, Inc. | Composition and method for surface refinement of titanium nickel |
US5154774A (en) * | 1985-09-19 | 1992-10-13 | Ugine Aciers De Chatillon Et Gueugnon | Process for acid pickling of stainless steel products |
US5158623A (en) * | 1990-03-30 | 1992-10-27 | Rem Chemicals, Inc. | Method for surface refinement of titanium and nickel |
US5690748A (en) * | 1991-02-25 | 1997-11-25 | Ugine Aciers De Chatillon Et Gueugnon | Process for the acid pickling of stainless steel products |
US5904157A (en) * | 1996-04-05 | 1999-05-18 | Phelps Dodge Industries, Inc. | Copper surface pickling system |
US6803354B2 (en) | 2002-08-05 | 2004-10-12 | Henkel Kormanditgesellschaft Auf Aktien | Stabilization of hydrogen peroxide in acidic baths for cleaning metals |
US20050233926A1 (en) * | 2004-04-05 | 2005-10-20 | Quantum Global Technologies, Llc | Etchants for removing titanium contaminant species from titanium substrates |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3008314C2 (en) * | 1980-03-04 | 1982-09-16 | MTU Motoren- und Turbinen-Union München GmbH, 8000 München | Process for activating titanium surfaces |
JPS58161780A (en) * | 1982-02-17 | 1983-09-26 | Kobe Steel Ltd | Method for preventing corrosion of ti in nitric acid solution |
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US2154469A (en) * | 1934-12-17 | 1939-04-18 | Du Pont | Bright dip |
US2154455A (en) * | 1934-02-08 | 1939-04-18 | Du Pont | Cadmium bright dip |
US2283170A (en) * | 1939-11-30 | 1942-05-19 | Batcheller Clements | Method of coloring etched stainless steel |
US2542727A (en) * | 1949-12-29 | 1951-02-20 | Bell Telephone Labor Inc | Etching processes and solutions |
US2577803A (en) * | 1948-12-29 | 1951-12-11 | Bell Telephone Labor Inc | Manufacture of semiconductor translators |
US2606960A (en) * | 1949-06-01 | 1952-08-12 | Bell Telephone Labor Inc | Semiconductor translating device |
US2711364A (en) * | 1953-12-31 | 1955-06-21 | John G Beach | Polishing metals and composition therefor |
US2740699A (en) * | 1949-07-23 | 1956-04-03 | Sylvania Electric Prod | Surface processing |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2724667A (en) * | 1955-01-14 | 1955-11-22 | Wayne Foundry & Stamping Co | Process of removing scale from titanium |
-
1956
- 1956-11-20 US US623316A patent/US2856275A/en not_active Expired - Lifetime
-
1957
- 1957-09-19 DE DEA27939A patent/DE1101899B/en active Pending
- 1957-10-16 FR FR1184446D patent/FR1184446A/en not_active Expired
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US2154455A (en) * | 1934-02-08 | 1939-04-18 | Du Pont | Cadmium bright dip |
US2154469A (en) * | 1934-12-17 | 1939-04-18 | Du Pont | Bright dip |
US2283170A (en) * | 1939-11-30 | 1942-05-19 | Batcheller Clements | Method of coloring etched stainless steel |
US2577803A (en) * | 1948-12-29 | 1951-12-11 | Bell Telephone Labor Inc | Manufacture of semiconductor translators |
US2606960A (en) * | 1949-06-01 | 1952-08-12 | Bell Telephone Labor Inc | Semiconductor translating device |
US2740699A (en) * | 1949-07-23 | 1956-04-03 | Sylvania Electric Prod | Surface processing |
US2542727A (en) * | 1949-12-29 | 1951-02-20 | Bell Telephone Labor Inc | Etching processes and solutions |
US2711364A (en) * | 1953-12-31 | 1955-06-21 | John G Beach | Polishing metals and composition therefor |
Cited By (19)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3125474A (en) * | 1964-03-17 | Pickling zirconium and zirconium base alloys | ||
US2981609A (en) * | 1956-11-20 | 1961-04-25 | United Aircraft Corp | Etching bath for titanium and its alloys and process of etching |
US3024095A (en) * | 1958-04-25 | 1962-03-06 | Nat Res Corp | Acid treatment of tantalum to remove surface irregularities |
US3082137A (en) * | 1958-12-03 | 1963-03-19 | Gen Motors Corp | Method and composition for etching titanium |
US2977204A (en) * | 1959-08-14 | 1961-03-28 | Donald W Shannon | Method of improving corrosion resistance of zirconium |
US3361674A (en) * | 1964-06-05 | 1968-01-02 | Bell Telephone Labor Inc | Copper etchant |
US3537895A (en) * | 1965-04-27 | 1970-11-03 | Lancy Lab | Copper and aluminum pickling |
US3450575A (en) * | 1968-01-17 | 1969-06-17 | Alexander J Riscky | Method of repairing heat cracks on ferrous metal engines |
US3905837A (en) * | 1972-03-31 | 1975-09-16 | Ppg Industries Inc | Method of treating titanium-containing structures |
US5154774A (en) * | 1985-09-19 | 1992-10-13 | Ugine Aciers De Chatillon Et Gueugnon | Process for acid pickling of stainless steel products |
US4754803A (en) * | 1987-02-02 | 1988-07-05 | Phelps Dodge Industries, Inc. | Manufacturing copper rod by casting, hot rolling and chemically shaving and pickling |
US4946520A (en) * | 1987-02-02 | 1990-08-07 | Phelps Dodge Industries, Inc. | Copper rod manufactured by casting, hot rolling and chemically shaving and pickling |
US4900398A (en) * | 1989-06-19 | 1990-02-13 | General Motors Corporation | Chemical milling of titanium |
US5051141A (en) * | 1990-03-30 | 1991-09-24 | Rem Chemicals, Inc. | Composition and method for surface refinement of titanium nickel |
US5158623A (en) * | 1990-03-30 | 1992-10-27 | Rem Chemicals, Inc. | Method for surface refinement of titanium and nickel |
US5690748A (en) * | 1991-02-25 | 1997-11-25 | Ugine Aciers De Chatillon Et Gueugnon | Process for the acid pickling of stainless steel products |
US5904157A (en) * | 1996-04-05 | 1999-05-18 | Phelps Dodge Industries, Inc. | Copper surface pickling system |
US6803354B2 (en) | 2002-08-05 | 2004-10-12 | Henkel Kormanditgesellschaft Auf Aktien | Stabilization of hydrogen peroxide in acidic baths for cleaning metals |
US20050233926A1 (en) * | 2004-04-05 | 2005-10-20 | Quantum Global Technologies, Llc | Etchants for removing titanium contaminant species from titanium substrates |
Also Published As
Publication number | Publication date |
---|---|
DE1101899B (en) | 1961-03-09 |
FR1184446A (en) | 1959-07-21 |
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