US2473614A - Method of and material for protecting and conditioning metal surfaces - Google Patents

Description

Patented June 21, 1949 METHOD OF AND MAT ING AND CONDITI FACES ERIAL FOR PROTECT- ONING METAL SUR- Eugene Snyder, Philadelphia, Pa., assignor to American Chemical Paint Company, Ambler, Pa., a corporation of Delaware No Drawing. Application December 13,1945,

Serial No. 634,891 I 7 Claims. (01. 148--6.15)

This invention relates to the art of finishing metal surfaces and is particularly concerned with that type of metal finishing which includes application to the surface of an organic coating such as paint, varnish, lacquer, japan or the like for either decorative or protective purposes. The invention is particularly applicable to the finishing of surfaces of iron, zinc, aluminum and of ironbase, zinc-base and aluminum base alloys.

The invention has for its purpose the attainment of the following objectives:

(a) The provision of a method and material for affording temporary protection to the surface against rusting, corrosion or contamination by atmospheric influences after the completion, or during the latterstages, of mechanical operations to which the metal objects may be subjected.

(b) The provision of a method and material for rendering any pre-existing light deposits of corrosion products or corrosion stimulative substances entirely innocuous either to the surface of the metal itself or to any subsequently applied organic coating.

The provision of a method and material for coating or conditioning the surface of the metal for the reception of the final organic finish so as to assure even retention, maximum adhesion and maximum life of the paint film either in use or during storage.

(d) The provision of a method and material for finishing metal surfaces in which the chemical reactions involved in conditioning the metal for the reception of the final paint film continue while the metal objects are in storage, in transit between diiferent locations within a plant or between dilferent plants or even while they are being subjected to machining or other mechanical operations.

(e) The provision of a method and material for use in conditioning metal surfaces for the reception of a final finish of paint and the like which makes vapor degreasing a safe and convenient step in the finishing process, in which connection it should be noted that vapor degreasing has not hitherto been entirely safe and practical where the parts are to be painted because of the deleterious effects of traces of hydrochloric acid which are often present in the vapors of the chlorinated solvents which are often encountered during the degreasing operation.

(I) The provision of a method and material I or use in the finishing of metal surfaces by means of which the amount of space and labor required as well as the degree of supervision necessary are greatly reduced and in general to provide a 2 method and material for use in the finishing of metal surfaces which is exceptionally simple, con-' venient and effective.

How the foregoing objectives to ether with any others which may appear hereinafter or are incident to my invention are attained will appear timately incorporated orthophosphoric acid in an .amount small compared with theamount of oily matter, together with such amounts of solvents, emulsifying agents, etc. as are necessary to obtain intimate incorporation or mutual solution of the oily matter with the acid.

(2) Allowing adhering material to remain upon the surface, not only until volatile solvents,

water, etc. have largely evaporated but also until the acid has had an opportunity to react with the metal to a substantial extent. The time neces-' sary for substantial reaction varies, of course, like all chemical reactions, with the temperature. It varies also with the viscosity of the oily part used, the length of time the solvents take to evaporate, etc. At room temperature (average living ternperature) or below I prefer to allow an hour or more to pass before proceeding to the next step since experiment has shown that this interval is necessary to assure optimum results. At elevated temperatures as little as five minutes or less may suffice.

Longer periods of drying of the composition of step 1 above do no harm. In fact, the materials are designed, as above indicated, to react with deleterious materials originally upon the surfaces to render them innocuous, to act chemically upon the surface, coating it or conditioning it for the reception of paint, and, finally to afford temporary protection against rust or corrosion during fabrication, storage, or shipping of the partly finished work. The chemical actions involved may not be completed for a long time, perhaps for days. Usually, however, the beneficial effects of the chemical action will be fully realized within the time indicated above, depending on the temperature.

(3) Removing the oil, fat, wax or similar substances from the surface without removing the chemical reaction products of the-material of step 1. This may be accomplished by washing the surface with a suitable organic solvent either greasr using ethylene trichloride.

'3 as such or in the form A very suitable method consists in condensing the vapor of the solvent upon the surface. This method, which may or may not be combined with simple washing in hot or cold solvent, is commonly known as "vapor degreasing." To avoid fire hazard it is usually carried out with chlorinated solvents such as trichlorethylene, perchlorethylene, carbon tetrachloride, etc.

This step of washing away the oily" part of I the coating is preferably carried out just prior to cautions are necessary in this step.

It will be found, as stated above, that the surface at this stage is excellent for the reception and retention of the paint.

By way of specific example I wish to cite the following.

A solution was prepared in accordance with the following formula:

Foams No. 1

Degras -pounds 3.000 Mineral spirits gallons 0.35 Pine il do 0.13 Monobutyi ether of ethylene glycol -do 0.13 85% phosphoric acid pounds 0.31

On thorough mixing the above composition made a clear brown solution. on standing, a little waxy material from the degras precipitated. No difilculty arose from the presence of this precipitate.

The metal articles to be treated were dipped for a short time into the solution of Formula No. 1, following which they were allowed to drain until no more of the composition dripped from them. and were then packed into boxes for shipment to another point for some mechanical treatment. The objects were in storage or en route for from two days to one week. depending upon the conditions obtaining at the time either in the plants or with the carriers.

After unpacking at the point of destination the objects were thoroughly degreased in a vapor de- They were then subjected to an operation entirely foreign to the finishing operation, following which they were sprayed with a conventional nitrocellulose lacquer formulated in accordance with a standard specification. My improved method and material re-' sulted in an excellent finish which met all specifications for adhesion of the lacquer, better than of an aqueous emulsion.

of cold-rolled annealed steel suitable for the manufacture of small stampings were treated at the mill with the composition of Formula No. 1. The material was applied to the blanks with an automatic paint spray gun, after which the blanks were packed and shipped to the factory where they were cut and stamped in a punch press into the completely formed articles. The articles were then washed with hot tetrachlorethyene, finally vapor degreased in the same solvent. and painted with two coats of a paint system of which each coat was applied by dipping and was force dried in an air oven. The paint system used included a primer based on alkyd resin and a top coat formulated with urea-formaldehyde resins.

Formula No. 1 above is formulated with degras as the oily" part which remains on. the metal surface after the solvents have evaporated. The film left on the surface includes the reaction products of the phosphoric acid and the metal, of

the degras and the metal, and residual degras itself. It is extremely adherent and protective and even affords surface protection under severe conditions'for relatively long periods of time. Degras is an example of so-called polar" compounds which impart to oily films relatively great corrosion-protective power.

Examples of compositions containing mixtures of degras and minor amounts of non-polar oily" parts are the following:

Foams No. 2

Degras pounds 3.00 Boya bean oil gallons 0.18 Mineral pir do 0.18 Butyl alcohol o 0.14 Monobutyl ether of ethylene glycol -do- 0.14 85% Phosphoricacld pounds 0.25

Foams No. 3

Degras pounds 2.30 Light mineral oil gallons- 0.14 Butyl alcohol do 0.22 Xylol do 0.17 Carbon tetrachloride do 0.17 85% Phosphoric acid pound 0.24

The above formulas all furnish consolute mix-' tures of the acid and the oily part in blends of solvents serving to bring all the ingredients into solution. Two further formulas are given below whic exemplify intimate admixtures of acid and degras which 'are not consolute but which exist as emulsions. Such emulsions are suitable for carrying out my improved finishing process provided they are sumciently stable and are thoroughly agitated before being applied to the metal surfaces, and

provided the composition spreads evenly over the surfaces, which surfaces may be somewhat greasy required life in accelerated testing, etc. In short the process was a considerable improvement over previous practice which had involved covering the objects with a light slushing oil during shipment. Furthermore. the objections heretofore resulting from contamination during the various handling 7 operations to which the objects were subiected were completely overcome because the objects arrived at the final plant in a condition which required no special rust removal before they could bepainted. In this way a great deal of extra space and labor as well as supervision were rendered unnecessary.

In another application of'my invention, blanks when the composition is applied.

Foiunms No. 4

Part A 7 Pounds Degras 3.333 Sorbitan mono-oleate polyalkylene derivative 0.417

Part B Gallons Water 4 0.97 Polyglycol ether derivative 0.03 Phosphoric acid 0.02 The degras is melted andthoroughly mixed with the sorbitan mono+oleate poiyalkylene derivative,

Foams No.

Part A Degras pounds 4.1 A sorbitan mono-oleate polyalkylene derivative "do 0.25 Xylol gallons 0.50

Melt degras, add the other ingredients and mix thoroughly.

Part B Gallons Water 0.97 A polyglycol ether derivative 0.01 85% phosphoric acid 0.03

Mix thoroughly. Pour Part A into Part B with violent stirring.

Formula No. 5 may be used as is, or may be thinned as desired with xylol.

The formulas given above are illustrative and are not meant to be limiting in scope. A suitable admixture'for carrying out my improved finishing process must merely conform to the following description 1. It must contain a substantial quantityof water-insoluble organic material the totality of which, if more than one is present, has an oily, greasy, or waxy consistency the principal component of which should be degras.

2. The "oily portion just described must be intimately admixed with phosphoric acid. The amount of phosphoric acid present in the admixture, calculated as pure HaPO4, should be between about 1 and 15% by weight of the oily part of the admixture, depending upon the amount of chemical action On the metal surface which is desired, and upon the reactivity of the metal. More acid than the upper limit set above yields irregular and rough reaction products which are likely to be injurious to the finish obtained.

3. Intimate admixture of the acid and the "oily portion may be obtained by using suitable mixtures of solvents to obtain homogeneous solutions, or by emulsifying together the acid and the oily part, or by other suitable means. Naturally, solvents will be selected which are reasonably stable to phosphoric acid and which have no deleterious effect on the metal surface to be finished.

Although the examples given above exemplify my process of finishing as it is carried out on steel, it is to be understood that it is also useful on aluminum and its alloys and on zinc or its alloys.

I claim:

1. A material for use in treating a surface of metal from the group consisting of iron, zinc, aluminum and of iron-base, zinc-base and aluminum-base alloys, the principal active ingredients of which material consist of an intimate admixture of degras and orthophosphoric acid together with a liquid vehicle for said admixture, the quantity of orthophosphoric acid being from 1 to by weight of the degras and the quantity of the vehicle being sufficient to obtain intimate incorporation of the degras with the acid.

2. The material of claim 1 in which said vehicle consists of organic solvents rendering the whole consolute.

3. The material of claim 1 in which the said admixture is formulated as an emulsion including water.

4. A method of finishing a surface of metal from the group consisting of iron, zinc, aluminum and of iron-base. zinc-base and aluminum-base alloys, which method consists in applying to the surface a material the principal active ingredients of which consist of an oily component, including degras as the principal oily constituent, intimately admixed with orthophosphoric acid in which the amount of acid, calculated as pure H3PO4 is between 1 and 15% by weight of the oily component; allowing adhering material to remain upon the surface until the phosphoric acid and the degras have reacted with the metal to a substantial extent; removing the oily component by washing the surface with an organic solvent; and applying to the washed surface a final coating of paint, varnish, lacquer, japan or the I like.

5. The method of claim 4 in which the material contains a volatile solvent system which renders it consolute.

6. The method of claim 4 in which the material is formed as an emulsion including water.

7. The method of claim 4 in which at least one hour elapses between the application of the material and its removal and in which the surface is A maintained at a temperature not higher than average living-room temperature during the elapsed interval.

EUGENE SNYDER.

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

UNITED STATES PATENTS c