US1965759A - Flux for galvanizing - Google Patents

Description

Patented July 10, 1934 FLUX FOB GALVANIZIN G Allen '1'. Baldwin, Mailman, n. 1., asaignol', by mesne assignments, to Hanson-Van Winkle- Munning Company, Matawan, N. 1., a corporation of New Jersey No Drawing. Application March 1, 1932, Serial No. 596,147

14 Claims. (Cl. 148-23) This invention relates to flux compositions useful, for example, in the hot dip galvanizing of iron and steel articles.

The particular improvement in fluxes which this invention contemplates is to insure a more advantageous foaming or frothing quality whereby certain important advantages are obtained.

lihe invention is applicable to any of the standard fluxing compounds such as salammoniac, zinc in chloride, zinc ammonium chloride, and the like, in which gases are set free either from the flux itself or from materials carried into the flux by the work. In most cases, the gases set free, such as for example hydrochloric acid, represent an 1 important constituent for the dissolving of zinc oxide, an effect which is essential to the successful operation of the flux. Whether such gases contribute the sole dissolving action or only an effect additional to the direct action of the flux at itself in dissolving zinc oxide, the loss of such gases from the flux layer constitutes an important loss in economy and may represent a considerable shortening in the life of a given quantity of flux material. This is especially true where the gas is :5 produced by the decomposition of the flux, as for example in the case of ammonium chloride or zinc ammonium chloride.

The principle underlying my present invention resides in the provision of a flux composition containing in addition to the primary or principal fluxing compound, an addition agent of such a nature that the generation or setting free of gas within the flux layer will develop a stable froth which will be sufiiciently pliable or mobile to 85 readily flow over the surface of the work which is being introduced through it and quickly cover any exposed areas of the molten zinc surface, while at the same time being sufllciently viscous to effectively prevent the loss of fumes and gases from the flux layer. In order that the proper consistency of flux layer may be definitely assured, and in order to further assure against the loss of any substantial quantity of fumes and gases during the initial spreading of the flux layer upon the molten zinc, the invention further contemplates in its preferred embodiment the admixture and uniform distribution of measured quantities of the frothing agent or stabilizer throughout the flux composition in the preparation of the composition for the market, so that the operator is supplied with an already mixed composition in proper proportions ready for use.

The flux composition, according to this invention, may comprise as its major component any of the standard fluxing compounds such as salammoniac,' zinc chloride, zinc ammonium chloride,

and the like, and a froth stabilizer in the form of a carbohydrate, especially a sugar, or a source of a sugar, such as a glucoside. In the selection of the stabilizer, due regard should, of course, be had to both its physical audits chemical properties. For example, the production of the mixture and the maintenance of a sufllcientl," uniform distribution of the ingredients in the market product make desirable the selection of materials which are normally solids, and preferably dry or substantially so. The use of the stabilizer on the molten zinc bath definitely prescribes the requirement that the stabilizer shall be substantially non-volatile at the temperatures encountered in the flux layer. It may be soluble or not in the liquid film of the froth, or produce colloidal suspensions therewith, so long as it has the property of being surface-active. The stabilizing function of this ingedient requires that it have the property of reducing the surface tension of the liquid film enclosing the gas in the froth bubbles, and imparting to the liquid film and to the resultant mass of froth the proper range of viscosity to effectively prevent the escape of gases and fumes while at the same time not producing too high a viscosity to prevent the froth from readily flowing over the work surface and freely closing any breaks in the froth layer. Due regard must likewise be had to the tendency of the stabilizer component to carbonize under the influence of the temperatures encountered in service, since excessive carbonization or too rapid carbonization may be injurious to the galvanizing operation. Obviously, the flux froth should not deteriorate or subside too rapidly.

Carbohydrates and glucosides have been found to meet the requirements to a very satisfactory degree. They may be employed successfully in such small proportions that even in the case of those which tend to carbonize, such as some of the sugars, the quantity involved is not sufficient for the free carbon to adversely affect the quality of the galvanizing operation.

Glucosides which I have found particularly satisfactory are licorice root, saponins and soapbark. Among the sugars I may employ, for example, a penta monose such as xylose, a hexa monose such as dextrose, a hexabiose such as cane sugar, or a polyose such as starch. Among the other glucosides which have been found to produce a satisfactory froth, I may mention, for example, amygdalin, phloridzin, populin, salicin, soap wort roots and tannin. Among other carbyhydrates which I have found to produce a satisfactory froth I may mention galactose, lactose, maltose and corn and potato starches.

The quantities of stabilizer employed may be as low as a fraction of one percent of the total mass of the flux itself. For example, in the case of zinc ammonium chloride, Zn(NH4):C14 or Zn(NH4)aCl5, satisfactory froths can be maintained by the use of one-half of one percent of any of the stabilizers mentioned. The upper limits of the quantity of stabilizer which maybe employed are not very definite, but satisfactory fluxes have been produced with zinc ammonium chloride including as high as six percent of stabilizer. Typical examples of compositions may be given as follows:-

1. Zinc ammonium chloride plus .5% to 1.5% soapbark. The upper limit of soapbark produces a flux of high stability and rather thick with bubbles of variable size, whereas the lower limit produces a thin froth which is not so suitable as the upper limit but still is satisfactory for galvanizing.

2. Zinc ammonium chloride plus .5% licorice root produces a very stable froth, rather thick with bubbles of variable size.

3. Zinc ammonium chloride plus .5% saponin produces a very stable, fine-bubble froth which forms very quickly on being spread over the molten zinc..

4. Zinc ammonium chloride plus .5% dextrose produces a satisfactory froth of fair stability and small bubbles.

5. Zinc ammonium chloride plus .5% cane sugar produces a satisfactory flux with fair stability and large bubbles.

6. Zinc ammonium chloride plus .5% xylose produces a very stable, small-bubble flux.

In each of the examples given, carbonization does not occur at an excessive rate or to any obiectionable extent.

Glucosides are generally more advantageous than carbohydrates. Concentrated extracts or pure compounds are more effective than equal quantities of the raw or crude materials containing them. Thus, while soapbark, at comparatively low cost, may be most advantageous in most cases, the concentrated extract in the'form known as saponin is more effective in equal amounts; and where the'price difference is not too great, it may even be an economy to use the saponin. The less extraneous material there is in addition to the effective component, the less will be the tendency of unfavorable eflects.

' such as for example too rapid carbonization. A bath f molten zinc comm-13mg ride selected from the group consisting of amsimilar principle applies in the case of carbohydrates which may on the one hand be employed in the form of crude raw. materials on account of low cost, but may advantageously be substituted by more pure or concentrated products.

Among the latter I find xylose and starch the stabilizer so that when spread over the molten zinc by the operator, there is an immediate or prompt formation of froth as the zinc ammonium chloride melts and gas is evolved. In the case of both zinc ammonium chloride and salammoniac, a decomposition occurs as a result of which ammonia and hydrochloric acid gas are evolved. These gases'are trapped in the liquid film of, for example, zinc chloride, the surface tension being decreased and the viscosity be ing increased due to the presence of the froth stabilizer. By the maintenance of a froth of sumcient depth, as for example from one to three or more inches, the proper temperature gradient may be maintained over the zinc bath. This is important in many ways, but it is particularly important for the insurance of an upper zone of temperature within the recombining range of ammonia and hydrochloric acid which are evolved at higher temperature from the decomposition of salammoniac. This froth retains not only gases evolved from the flux itself, but those produced from materials carried in with the work, such as for example hydrochloric acid from the chloride wash treatment preparatory to galvanizing. Water vapor may likewise be present. Where the work is introduced wet, which -ing agents of the character set forth to the flux material being prepared by the operator at the galvanizing plant, the ingredients being brought together either before application to the zinc bath or during the building 'of'the froth layer upon the zinc bath; Supplemental additions of either ingredient may" be made to restore or rejuvenate a depleted or'deteriorated flux, as may be found necessary or desirable. Also, the invention does not exclude the use of more than one of the frothing agents, as obviously two or more may be used together in a given flux so long as they are not incompatible. i

'Iclaim:- 1. A prepared flux composition for use on a -galvanizing bathof molten zinc, consisting substantially of a chloride selected from the group consisting of ammonium chloride, zinc chloride and zinc ammonium chloride, and a small admixture of a broth stabilizer selected from the group consisting of glucosides and carbohydrates partially or wholly soluble in water.

2. A prepared flux composition for use on a galvanizing bath of molten zinc, comprising a chloride selected from the group consisting of ammonium chloride, zinc chloride and zinc ammonium chloride, and a small admixture of a glucoside as a froth stabilizing ingredient.

3. A prepared flux composition for use on a galmonium chloride, zinc chloride and zinc ammonium chloride, and a-small admixture of soapbark as a froth stabilizing ingredient.

4. A prepared flux composition for use on a galvanizing bath of molten zinc, comprising a chloride selected from the group consisting of ammonium chloride, zinc chloride and zinc am monium chloride, and a small admixture of sawnin as a froth stabilizing ingredient.

5. A prepared flux composition for use on a galvanizing bath of molten zinc, consisting substantially of a chloride selected from the group consisting of ammonium chloride, zinc chloride and zinc ammonium chloride, and a small admixture of a carbohydrate partially or wholly soluble in water as a froth stabilizing ingredient.

6. A prepared flux composition for use on a galvanizing bath of molten zinc, comprising a chloride selected from the group consisting of ammonium chloride, zinc chloride and zinc ammonium chloride, and a small admixture of xylose as a froth stabilizing ingredient.

7. A prepared flux composition for use on a galvanizing bath of molten zinc, comprising a chloride selected from the group consisting of ammonium chloride, zinc chloride and zinc ammonium chloride, and a small admixture of starch as a froth stabilizing ingredient.

8. A prepared flux composition for use on a galvanizing bath of molten zinc, consisting substantially of zinc ammonium chloride and a small admixture of a froth stabilizer selected from the group consisting of glucosides and carbohydrates partially or wholly soluble in water.

9. A prepared flux composition for use on a galvanizing bath of molten zinc, comprising zinc ammonium chloride and a small admixture of a glucoside as a froth stabilizing ingredient.

10. A prepared flux composition for use on a galvanizing bath of molten zinc, comprising zinc ammonium chloride and a small admixture of soapbark as a froth stabilizing ingredient.

11. A prepared flux composition for use on a galvanizing bath of molten zinc, comprising zinc ammonium chloride and. a small admixture of saponin as a froth stabilizing ingredient.

.12. A prepared flux composition for use on a galvanizing bath of molten zinc, consisting sub- ALLEN T. BALDWIN.