US2473579A - Foaming-type galvanizing fluxes and processes employing them - Google Patents

Description

Patented June 21, 1949 FOAMTING-TYPE GALVANIZING FLUXES AND PROCESSES EMPLOYING THEM Lowell D. Eubank, Richland, Wash., assignor to E. I. du Pont de Nemours & Company, Wilmington, DeL, a. corporation of Delaware No Drawing. Application January 4, 1945, Serial No. 571,374

Claims. (Cl. 148-23) This invention relates to galvanizing fluxes and processes and more particularly to novel foaming fluxes having excellent fluidity and comprising a chloride, selected from the group consisting of ammonium chloride and zinc ammonium chloride, and an organic compound having from one to two aromatic, carbocyclic, G-membered rings directly joined to two carbonyl substituent groups, and is further particularly directed to galvanizing processes employing such fluxes.

In galvanizing practice it is customary to add a small amount of an organic material to the ammonium chloride or zinc ammonium chloride flux to produce a frothy layer on the surface of the molten metal in the galvanizing pot. A flux which in use forms such a frothy layer is known as a foaming flux. Organic materials commonly used to cause foaming are bran, glycerol, tallow, or saw-dust. Inclusion of a foaming agent in a flux is ordinarily considered desirable because it retards decomposition of the flux, preheats incoming articles, and reduces spattering of molten metal.

"Unfortunately, the foaming agents hitherto widely used have the disadvantage that after a period of use they thicken the flux and cause it to become viscous. This loss in fluidity is objectionable for a number of reasons. It retards the rate of wetting of the incoming work by the flux, which often results in failure to obtain complete coverage of the work and leads to imperfect galvanizing. In increases the rate at which flux is carried out on the finished work and complicates subsequent cleaning. It makes proper handling of the flux much more dimcult. These and other objections to a viscous flux have caused some galvanizers in certain situations to prefer a non-foaming flux, despite the known advantages of foaming fluxes.

According to the present invention it has been found that by adding certain organic compounds to ammonium chloride or zinc ammonium chloride there are produced galvanizing fluxes which are of the foaming type but which remain remarkably fluid during use. The organic compounds effective to produce this result are compounds which have from one to two aromatic, carbocyclic, G-membered rings directly joined to two carbonyl substituent groups. A further aspect of the invention consists of galvanizing processes employing such fluxes. The processes enjoy the advantages attending the use of a foaming flux but are not subject to the disadvantages heretofore ordinarily encountered. Moreover, by the use of a prepared flux composition of this invention the necessity of determining in the galvanizing shop the quantity of foamer to use is avoided.

To make a flux of this invention there is added to a major proportion of ammonium chloride or zinc ammonium chloride a minor proportion of the selected organic compound as a foamer. If too large a proportion of the foaming agent is used the flux will foam excessively and be difficult to use, While if the proportion is too small the advantages of the invention will not be fully realized- It has been found that the foaming agents herein described are extremely effective and it is preferred to employ about from 0.1 to 1.0 per cent by weight based on the ammonium chloride or zinc ammonium chloride.

The foamer may be added to the molten ammonium chloride or zinc ammonium chloride fluxing agent on the molten metal in the galvanizing pot. However, this involves the problem of distribution; that is, time and attention is required to insure a uniform distribution of the foamer throughout the fluxing agent. It is therefore preferred to incorporate the foamer in the fluxing agent prior to adding the flux to the galvanizing pot. This may be done by adding the foamer to the granular ammonium chloride or zinc ammonium chloride with mechanical agitation as, for instance, in a tumble mill. The products so produced are fluxes of maximum economy which can be used in the galvanizing plant with assurance of uniformity and without the close supervision attending the proportioning of the ingredients at the point of use.

In the following table are shown several examples of compounds which have been found to be effective as foamers in the fluxes of this invention, together with their structural formulae, and the concentration ,of the agent, by weight, reouiredin an ammonium chloride flux to give a froth on a galvanizing bath during use equiva- 3 lent to the froth produced by 1.37% tallow, a foamer heretofore commonly employed.

Per Cent Compound Formula Concentratlon Phthalic anhydrlde C") 0.25

Disodium phthaiate E) 0.36

(fi-ONa O Anthraquinone (I? 0. 72

l'hydroxyanthraquinone. 0 0. 50

it; OK G 1! 0 Anthrarufin O 0. 42

(I; OH

1,4 diamino anthracluimme. v 0

I NH O 1 1,4 dihydroxy anthraquinone O 0. 46

H OH G 1 amino. 4l1ydroxy anthra- 0 0. 46

quinone. fl NH:

g/ g H 1 amino, 2 methyl anthrao o. is

quinone. ([5 NH:

The foregoing compounds are all organic compounds having at least one aromatic, carbocyclic, 6-membered ring directly joined to at least two carbonyl substituent groups. In the case of phthalic anhydride the carbonyl groups are both attached to a single oxygen as well as being attached to the six membered aromatic ring. In the case of anthraquinone the two carbonyl groups link together two S-membered aromatic rings but, regarding each G-member ring separately it will be seen that the G-member ring is twice substituted with carbonyl groups. Thus, for the purposes of the formula, the carbonyl group,

is regarded as a substituent irrespective of whether or not it may be a part of a larger structure.

The practice of this invention will be better understood by reference to the following illustrative example:

Example Into the flux boxes of a continuous strip galvanizing pot, on the surface of the molten zinc, there was placed a quantity of a flux of this invention sufiicient to produce a frothy layer about 15 inches deep in the input box and about 1 inch deep in the exit box. The flux used consisted of ammonium chloride containing 0.25% of its weight of phthalic anhydride. Initially the molten flux layer had a viscosity of about 25 centipoises.

The galvanizing pot and flux bath were then used for galvanizing a quantity of strip steel, the steel being introduced continuously into the molten zinc through the frothing flux in the input flux box, then passing beneath the surface of the molten metal and out of the pot through the exit flux box. During the operation additional flux was added as required to maintain the flux layer in each box at its original depth. At the end of eight hours of such operation the viscosity of the flux had risen to 92 cps. and the flux was still sufficiently fluid to be effective, that is, it was still a live flux.

For comparison, a similar operation was conducted in the same equipment under the same conditions and on the same type of work but using an ammonium chloride flux containing 1.37% of tallow as a foaming agent. Although this flux had about the same initial viscosity, that is, about 28 cps, it was found that more frequent additions of flux during use were required to maintain the desired foam blanket, and after 6% hours the viscosity had risen to 100 cps. and the flux was considered dead. During the 6% hour period of use the quantity of flux added to this bath was 10% greater than that added in the case of the phthalic anhydride-containing flux during the corresponding period.

The galvanized sheet produced using the phthalic anhydride-containing flux was uniformly well galvanized, being remarkably free of flux spots. In general, the amount of phthalic anhydride-containing flux carried out on the galvanized sheet was noticeably less than the amount of tallow-containing flux carried out under corresponding conditions.

While in the foregoing description of this invention there have been shown certain particular compositions and processes, it will be understood that without departing from the spirit of the invention one skilled in the art may employ numerous compositions and processes.

I claim:

1. A foaming-type galvanizing flux comprising a fiuxing agent, selected from the group consisting of ammonium chloride and zinc ammonium chloride, and from 0.1 to 1.0% by weight of an organic compound having from one to two aromatic, carbocyclic, G-membered rings directly joined to two carbonyl substituent groups.

2. A foaming-type galvanizing flux comprising ammonium chloride and about from 0.1 to 1.0% by weight, based on the weight of ammonium chloride, of an organic compound having from one to two aromatic, carbocyclic, B-membered rings directly joined to two carbonyl substituent groups.

3. A foaming-type galvanizing flux comprising ammonium chloride and phthalic anhydride, the proportion of phthalic anhydride being about from 0.1 to 1.0% by weight of the ammonium chloride.

4. A foaming-type galvanizing flux comprising ammonium chloride and disodium phthalate, the proportion of disodium phthalate being about from 0.1 to 1.0% by weight of the ammonium chloride.

5. A foaming-type galvanizing fiux comprising ammonium chloride and purpurin, the proportion of purpurin being about from 0.1 to 1.0% by Weight of the ammonium chloride.

6. In a galvanizing process, the step comprising subjecting the work to be galvanized to contact with a flux comprising a fluxing agent, selected from the group consisting of ammonium chloride and zinc ammonium chloride, and from 0.1 to 1.0% by weight of an organic compound having from one to two aromatic, carbocyclic, 6- membered rings directly joined to two carbonyl substituent groups.

'7. In a galvanizing process, the step comprising subjecting the work to be galvanized to contact with a flux comprising ammonium chloride and about from 0.1 to 1.0% by weight, based on the Weight of ammonium chloride, of an organic compound having from one to two aromatic, carbocyclic, G-membered rings directly joined to two carbony1 substituent groups.

8. In a galvanizing process, the step comprising subjecting the work to be galvanized to contact with a flux comprising ammonium chloride and phthalic anhydride, the proportion of phthalic anhydride being about from 0.1 to 1.0% by weight of the ammonium chloride.

9. In a galvanizing process, the step comprising subjecting the work to be galvanized to contact with a flux comprising ammonium chloride and disodium phthalate, the proportion of disodium phthalate being about from 0.1 to 1.0% by weight of the ammonium chloride.

10. In a galvanizing process, the step comprising subjecting the work to be galvanized to contact with a flux comprising ammonium chloride and purpurin, the proportion of purpurin being about from 0.1 to 1.0% by Weight of the ammonium chloride.

LOWELL D. EUBANK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,111,226 Russell Mar. 15, 1938 2,117,649 Boyle May 17, 1938