GB1588912A

GB1588912A - Method for the organic phosphating of metal surfaces and a device therefor

Info

Publication number: GB1588912A
Application number: GB1583678A
Authority: GB
Original assignee: MARIN IND SpA; SCEAR CONTINENTALE
Current assignee: MARIN IND SpA; SCEAR CONTINENTALE
Priority date: 1977-05-12
Filing date: 1978-04-21
Publication date: 1981-04-29
Also published as: IT1107730B; DE2818160A1; FR2390513A1

Description

(54) AN IMPROVED METHOD FOR THE ORGANIC PHOSPHATING OF METAL SURFACES AND A DEVICE THEREFOR (71) We, CAMPAGNIA CONTI NENTALE S.C.E.A.R., S.R.L., a Body Corporate organised under the laws of Italy, of Via Tagiura, 9-20146 Milano -- Italy, and INDUSTRIALE MARIN S.P.A., a Body Corporate organised under the laws of Italy, of Corso Vercelli, 25-20100 Milano -- Italy, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to an improved method for the organic phosphating of metal surfaces and a device for carrying out said method.

It is well known that the term "organic phosphating" means a cold process for pretreating ferrous and non-ferrous metals, and the alloys thereof, by depositing onto the surfaces of said metals iron and zinc phosphates, coated by a polymeric film.

A feature of this organic phosphating process or method is that it allows for the treating of any oil or grease-contaminated metal structure, without the need of carrying out a preliminary degreasing operation.

Said process comprises, essentially, a continuous or batch immersion of the pieces to be treated in suitable vats containing the treating solutions. In operation the aforesaid contaminating compounds do not affect the phosphating process, thereby the operation of the treating vats may theoretically be unlimited.

The main drawback of the known phosphating methods is that in these methods, the impurities consisting of metal slugs or scales, other deposits, carbonized soaps or greases are not completely removed during treatment.

Accordingly the surfaces of the metals treated by the known phosphating methods are not suitable for those industrial products in which a great amount of finishing is required.

As well known, the defects due to the pres ence of the aforesaid impurities on the sur face of the treated metals are enhanced in all painting operations as carried out by primers or finishing enamels, in aqueous or organic solvents, and by products free of solvents and based on powder material.

Another drawback is due to the fact that the treating times for organic phosphating, while smaller than those required by alternative methods of preparation such as the inorganic phosphating or the simple removal or elimination of the oil contaminating elements or greases, are comparatively long, and therefore very costly.

Accordingly, it is an object of the present invention to provide an organic phosphating method and a device therefor, which is free of the aforesaid drawbacks.

The applicants have found that this and other objects, which will become more apparent from the following description, are achieved by carrying out the organic phosphating method in the presence of ultra-sonic waves.

According to the invention we provide a method for phosphating a metal workpiece comprising immersing the workpiece in an organic phosphating solution, subjecting the solution and workpiece to ultrasonic waves at a frequency from 18 to 50 KHz from at least two sources located in the solution at opposing positions or from one source movable in the solution, each source being provided with a radiating plate, and recirculating the solution through a filter.

Also according to the invention we provide an apparatus for phosphating a metal workpiece comprising a vat to contain a phosphating solution, means for producing ultrasonic waves in the solution at a frequency from 18 to 50 KHz, said means including either at least two sources of said waves at opposing positions or one source movable in the solution, each source being provided with a radiating plate and means for recirculating the solution through a filter.

The presence of the ultrasonic waves, as the organic phosphating method is carried out, enables the contaminating elements and the impurities to be completely removed from the surfaces of the pieces to be treated, thereby rendering said pieces suitable for all the industrial applications.

The supersonic wave sources may be both of magnetostrictive type and piezoelectric type, with power varying from 0.2 to 12 KW and with frequencies between 18 and 50 KHz.

In practice better results are obtained by using supersonic wave sources consisting of transducing members operating on the physical principle of magnetostriction in a frequency range from 19 to 20 KHz, said transducing elements being provided with radiating plates supplying an ultra-acoustic power of from 1 and 1.5 W/cm2.

The transducing element size or, in general, the size of the supersonic wave sources, the attitude thereof and the volume of the vat, vary depending on the geometric shape of the pieces to be treated, the translation speed of said pieces (for the continuously operating systems) and the types of the contaminating elements and solid impurities to be removed.

The treating of metal surfaces according to the method of the present invention enables the complete elimination of oil contaminating elements and greases, carbonized soaps or greases, and solid contaminating elements such as filings, slags and powders.

The time for carrying out the organic phosphating method or process of the present invention is greatly reduced with respect to the conventional method, due to the cavitation effect of the supersonic waves on the treating polyphosphate liquid.

In fact, under this treatment, the liquid is able both to remove the contaminating elements and to deposit the phosphate protective layer with a faster speed. Thus, for example, the treating time may be reduced to 20 -"0 sec. for small size surfaces.

Moreover, the deposited phosphate layer, due to the supersonic action, assumes a better crystalline attitude involving a decrease in the roughness of the treated pieces.

It has been found experimentally that the action of the supersonic waves enables the contaminating elements and impurities to be removed, these, after removal from the surfaces of the pieces, accumulating in the treating vat.

In fact, since these impurities are subjected to high pressures due to the cavitation effect, they agglomerate, and may be easily removed from the treating bath.

The characteristic, functional and structural features of the organic phosphating device of the present invention will become more apparent from the following description in which reference is made to the figures of the accompanying drawings illustrating two preferred but non-limiting embodiments of the present device, where: Fig. 1 is a schematic view of a device for the continuous phosphating of metal pieces; Fig. 2 is a schematic view of a device for phosphating single metal pieces.

Referring to the figures of the accompanying drawings, the device for carrying out the organic phosphating method of the present invention comprises a vat 1 which is externally and laterally provided with a slanted plane 2 for collecting the liquid drops from the treated pieces.

The vat 1 which may be optionally inserted in a suitable trench (Fig. 2) is provided with a removable bottom plate 3 for collecting deposits of impurities and, it is located on the ground (Fig. 1), it is provided with a valve 4 for a bottom discharge.

The polyphosphate treating solution, contained in the vat 1, is withdrawn by a pump 5 from one end of the vat through a large mesh filter 6 and, by a filtering assembly 7, is conveyed to the opposite end of the vat by means of a duct 8 provided with a gate 9.

In the case of continuously operating devices (see Fig. 1) a suitably extending rail 10 is located above the vat along which the metal pieces to be treated are caused to slide by means of a suitable chain.

In the inside of the vat 1 at least two ultrasonic transducing elements 11 and 11' are located at opposing positions.

In the case of devices for single treatments (see Fig. 2) a rail is located on one of the longitudinal edges of the vat 1, there being a carriage 13 sliding along the rail 12 and supporting an ultrasonic transducing element 14.

In both embodiments illustrated in Figs. 1 and 2 the instant devices are provided with an aspirator 15 adjacent plane 2, the aspirator 15 being effective to evaporate any liquid adhering to the treated metal piece.

In carrying out the present invention several changes and modifications may be brought about within the teachings of the present invention and without departing from the scope thereof as defined by the appendant claims.

WHAT WE CLAIM IS: 1. A method for phosphating a metal workpiece comprising immersing the workpiece in an organic phosphating solution, subjecting the solution and workpiece to ultrasonic waves at a frequency from 18 to 50 KHz from at least two sources located in the solution at opposing positions or from one source movable in the solution, each source being provided with a radiating plate, and recirculating the solution through a filter.

2. Apparatus for phosphating a metal workpiece comprising a vat to contain an organic phosphating solution, means for producing ultrasonic waves in the solution at a frequency from 18 to 50 KHz. said means including either at least two sources of said waves at

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. enables the contaminating elements and the impurities to be completely removed from the surfaces of the pieces to be treated, thereby rendering said pieces suitable for all the industrial applications. The supersonic wave sources may be both of magnetostrictive type and piezoelectric type, with power varying from 0.2 to 12 KW and with frequencies between 18 and 50 KHz. In practice better results are obtained by using supersonic wave sources consisting of transducing members operating on the physical principle of magnetostriction in a frequency range from 19 to 20 KHz, said transducing elements being provided with radiating plates supplying an ultra-acoustic power of from 1 and 1.5 W/cm2. The transducing element size or, in general, the size of the supersonic wave sources, the attitude thereof and the volume of the vat, vary depending on the geometric shape of the pieces to be treated, the translation speed of said pieces (for the continuously operating systems) and the types of the contaminating elements and solid impurities to be removed. The treating of metal surfaces according to the method of the present invention enables the complete elimination of oil contaminating elements and greases, carbonized soaps or greases, and solid contaminating elements such as filings, slags and powders. The time for carrying out the organic phosphating method or process of the present invention is greatly reduced with respect to the conventional method, due to the cavitation effect of the supersonic waves on the treating polyphosphate liquid. In fact, under this treatment, the liquid is able both to remove the contaminating elements and to deposit the phosphate protective layer with a faster speed. Thus, for example, the treating time may be reduced to 20 -"0 sec. for small size surfaces. Moreover, the deposited phosphate layer, due to the supersonic action, assumes a better crystalline attitude involving a decrease in the roughness of the treated pieces. It has been found experimentally that the action of the supersonic waves enables the contaminating elements and impurities to be removed, these, after removal from the surfaces of the pieces, accumulating in the treating vat. In fact, since these impurities are subjected to high pressures due to the cavitation effect, they agglomerate, and may be easily removed from the treating bath. The characteristic, functional and structural features of the organic phosphating device of the present invention will become more apparent from the following description in which reference is made to the figures of the accompanying drawings illustrating two preferred but non-limiting embodiments of the present device, where: Fig. 1 is a schematic view of a device for the continuous phosphating of metal pieces; Fig. 2 is a schematic view of a device for phosphating single metal pieces. Referring to the figures of the accompanying drawings, the device for carrying out the organic phosphating method of the present invention comprises a vat 1 which is externally and laterally provided with a slanted plane 2 for collecting the liquid drops from the treated pieces. The vat 1 which may be optionally inserted in a suitable trench (Fig. 2) is provided with a removable bottom plate 3 for collecting deposits of impurities and, it is located on the ground (Fig. 1), it is provided with a valve 4 for a bottom discharge. The polyphosphate treating solution, contained in the vat 1, is withdrawn by a pump 5 from one end of the vat through a large mesh filter 6 and, by a filtering assembly 7, is conveyed to the opposite end of the vat by means of a duct 8 provided with a gate 9. In the case of continuously operating devices (see Fig. 1) a suitably extending rail 10 is located above the vat along which the metal pieces to be treated are caused to slide by means of a suitable chain. In the inside of the vat 1 at least two ultrasonic transducing elements 11 and 11' are located at opposing positions. In the case of devices for single treatments (see Fig. 2) a rail is located on one of the longitudinal edges of the vat 1, there being a carriage 13 sliding along the rail 12 and supporting an ultrasonic transducing element 14. In both embodiments illustrated in Figs. 1 and 2 the instant devices are provided with an aspirator 15 adjacent plane 2, the aspirator 15 being effective to evaporate any liquid adhering to the treated metal piece. In carrying out the present invention several changes and modifications may be brought about within the teachings of the present invention and without departing from the scope thereof as defined by the appendant claims. WHAT WE CLAIM IS:

1. A method for phosphating a metal workpiece comprising immersing the workpiece in an organic phosphating solution, subjecting the solution and workpiece to ultrasonic waves at a frequency from 18 to 50 KHz from at least two sources located in the solution at opposing positions or from one source movable in the solution, each source being provided with a radiating plate, and recirculating the solution through a filter.

opposing positions or one source movable in the solution, each source being provided with a radiating plate and means for recirculating the solution through a filter.

3. Apparatus as claimed in clalm 2 wherein the vat has a removable bottom plate.

4. Apparatus as claimed in claims 2 or 3 in which the waves sources are of magnetostrictive or piezoelectric type with power varying from 0.2 to 12 Kw.

5. Apparatus according to claims 2, 3 or 4, wherein the wave sources comprise transducing elements operating in a frequency range from 19 to 20 KHz and the radiating plates supplying a supersonic power between 1 and 1.5 W/cm2.

6. Apparatus according to any of claims 2 to 5, having a rail above said vat effective to transport the workpiece.

7. Apparatus according to any of the preceding claims 2 to 6, wherein the single supersonic wave source slides in the vat along a rail located on one of the vat longitudinal edges.

8. Apparatus according to any of the preceding claims 2 to 7, wherein said vat is provided, on the upper edge thereof, with a slanted plane and an aspirator for evaporating the liquid phase of the treated workpiece.

9. Apparatus for carrying out the phosphating of the surfaces of metal workpieces substantially as described and as illustrated in Figures 1 or 2 of the accompanying drawings.