BRPI1105661A2 - COMPOSITION FOR PRE-TREATING AN ALUMINUM SURFACE, METHOD FOR PREPARING AND APPLYING COMPOSITION, USE OF COMPOSITION AND PRODUCT - Google Patents

Abstract

COMPOSITION FOR PRE-TREATING AN ALUMINUM SURFACE, METHOD FOR PREPARING AND APPLYING COMPOSITION, USE OF COMPOSITION AND PRODUCT. The present invention relates to an aluminum surface pretreatment composition, characterized in that it is an aqueous solution composed of 2% to 10% of a fluorinated inorganic acid by weight; 2% to 10% alkali or alkaline earth metal molybdate, titanate or zirconate or ammonia, optionally in the form of fluorine by weight derivative and 0.02 to 0.2% of an oxidizing agent source relative to the total weight of the composition . The present invention further describes a method for preparing and applying the composition on an aluminum surface.

Description

Report of the Invention Patent for "COMPOSITION FOR PRE-TREATING AN ALUMINUM SURFACE, METHOD FOR PREPARING AND APPLYING COMPOSITION, USE OF COMPOSITION AND PRODUCT".

Field of the invention

The present invention relates to an aqueous solution used in the pretreatment of aluminum and its alloys in order to make its surface suitable for application of a selected paint system.

More particularly, the present invention describes a composition free of chromium and toxic derivatives, as well as a method for preparing said composition and further a method for its application on an aluminum surface during the chemical treatment step.

Finally, the present invention also relates to the use of said composition and a product whose surface is treated with the composition described above.

Description of the prior art

Aluminum and its alloys have been in use since 1886, and although aluminum is the third most abundant chemical element in the earth's crust, its current production exceeds the sum of all other nonferrous metals. Additionally, its manufacturing techniques allow the finished product to be manufactured at competitive prices, and its main and most economical raw material for industrial use is bauxite ore.

Although it is the youngest metal used on an industrial scale, aluminum has unmatched properties and excellent performance in most applications, such as low density and mechanical strength. In this sense, despite having only one third of the weight of steel, its mechanical properties are equivalent.

Products utilizing aluminum and its alloys incorporate the inherent advantages of metal such as lightness, electrical and thermal conductivity, impermeability and opacity, high strength to weight ratio, beauty, durability, moldability and weldability, corrosion resistance, toughness. and hardness, recyclability and possibility of many finishes.

Several segments use aluminum and its alloys in the form best suited to their purposes, taking advantage of the metal's properties in accepting various types of surface treatment. In this context, aluminum and its products can be applied in the packaging, transportation, electricity, civil construction, consumer goods, machinery and equipment and other segments.

Importantly, aluminum and its alloys can be used with or without finishing processes. That is, for some applications, the natural finish of aluminum is totally satisfactory, both in appearance and durability. For metal frame applications (doors, windows, facades, railings, shower stalls, etc.), furniture (kitchen cabinets, closets, bedroom cabinets, etc.), consumer goods (refrigerators, stoves, microwaves, washing machines, etc.), transports (open and closed bodies, trunk-type bodies, accessories, etc.) decoration items (chandeliers, sconces, mirrors, door handles, etc.), among other applications , the aluminum surface requires proper protection and decoration finish.

In general, the properties of aluminum do not allow paint to adhere directly to its surface. To apply a paint, its extension must be pre-treated in order for a conversion layer to be created by chemical treatment in order to prepare aluminum for paint adhesion. If the pretreatment is adequate, the paint will have a good grip, with no risk of loosening while cutting the edges of the aluminum. Furthermore, said conversion layer is capable of providing high corrosion resistance.

Therefore, the durability of the paint on an aluminum surface depends especially on the adhesion of the paint and the resistance of the metal to corrosion, properties which can be conferred by the conversion layer formed during pretreatment.

The painting of an aluminum surface is performed in the pre-treatment finishing stage and is very important for the coating of some products, especially for cases where the metal is used for decorative and protective purposes.

The coating can increase surface wear resistance or extend the corrosion protection of an aluminum surface, and its efficiency depends on the preparation of the receiving surface. A well-cleaned surface - free of oxidation, grease, dirt and moisture - and with a uniform conversion layer is considered a substrate capable of receiving a protective or decorative finish.

The process of finishing an aluminum surface can be carried out in more than one way. As an example of finishing, mechanical abrasion is considered a relevant process, however, a special configuration of the parts to be treated gives difficulties to the technique. More specifically, in these types of parts there are dead angles, "shadows" that do not allow uniform abrasion jet access to all surface points of a metal part. Thus, mechanical abrasion does not achieve satisfactory homogeneity for the subsequent application of a paint film on the aluminum surface.

Another example is the abrasion performed manually. However, this technique has disadvantages such as high labor cost and longer time to achieve satisfactory abrasion.

Anodizing is also part of the relationship of surface-to-surface processes of an aluminum whereby a natural oxide film is artificially produced in aluminum by means of the anode of an electrolyte. The newly formed anodic film, prior to the final sealing stage, is porous and can absorb staining material. This is the basis of most anodized color finishes and enables printing in certain areas, clearly reproducing small details. However, this technique presents a high cost of manufacturing the formed film, so that such disadvantage makes the present application commercially unfeasible. Naturally colored anodizing is also often

employed to provide additional corrosion resistance. The film is uniform and hard, and aluminum interior fittings such as door knobs are often anodized to increase their wear resistance. This property is further explored in hard anodizing, in which a dense multi-micrometer thick film is developed by means of refrigerated electrolyte treatment for use on aircraft inlets that are subject to the abrasive effects of dust. of the airfields. Although a technique that has superior corrosion resistance is present, the high cost of manufacturing the formed film makes this application commercially unfeasible.

It is therefore well known to one skilled in the art that an aluminum surface needs some kind of proper finishing in order to receive a particular paint, since metal does not, by itself, provide favorable conditions for coating with an ink film.

When a chemical treatment is used during pretreatment, the conversion layer formed is capable of either transforming an aluminum surface into a bad conductor or isolating the metal surface of the subsequently applied paint film. In the absence of chemical treatment, the metal surface remains conductive under the coating layer, so that the electric current flows freely between any electrodes on the metal surface and also enables corrosion to occur.

Pretreatment is intended to remove all impurities present in aluminum (antioxidant oils, lubricants, grease, metal oxides, etc.) in order to make the metal surface receptive to coatings to be applied later. Overall, a good cleaning process ensures full physical contact between the aluminum surface and the pretreatment solution for forming the conversion layer.

Currently, the aluminum surface cleaning protocol consists of the sequence comprising the steps described in Brazilian Standard ABNT NBR 14125 of i) degreasing, ii) first washing; iii) deoxidation; iv) second washing; v) conversion / chromatization, vi) third wash, vii) wash with demineralized water and viii) drying, which will be described in more detail below.

Degreasing step (i) may be carried out with the aid of an alkaline solution or an acid solution.

Degreasing via an alkaline solution occurs when the solution

Generally used is a mixture of alkaline salts and one or more water solubilized emulsifiers. The components chosen should decrease the surface tension of water in order to facilitate the removal and subsequent emulsification of oils and greases present, making them easily rinsed.

The application of this alkaline solution is commonly performed by immersion, but the application by means of sprays becomes more efficient by incorporating the detergent action of the alkaline cleaning solution to the mechanical action of the directed jets. At the end of this first step of degreasing via alkaline solution,

a minimum removal (stripping) of 1 g / m2 of metal surface must be ensured. Finally, this degreasing must allow saponification or emulsification of previously present oils and greases, ensure perfect wetting of a metal surface and eliminate any aluminum oxide that may be present.

Degreasing via an acidic solution occurs when the solution used is applied at room temperature, in order to promote the cleaning of the metallic surface of present oils and greases.

Similar to the application of an alkaline solution, at the end of this first degreasing step via acid solution, a minimum removal (stripping) of 1 g / m2 of metallic surface must be ensured.

The first, second and third wash steps (ii, iv and vi) are designed to remove excess solutions from the previous steps that may remain on the aluminum surface, thus avoiding contamination of the later steps by dipping. of the treated metal surface in a water bath. These steps are of fundamental importance and the contamination level of the washings must be controlled through a continuous renewal of their water volume.

The deoxidation step (iii) is the process of removing the oxides from the aluminum surface, as they are undesirable for subsequent treatments.

Following the cleaning steps previously described, one method is

usually applied on the production line to ascertain the level of cleanliness of the metal surface. This method consists in verifying that the metallic surface is free of "water break", that is, if the surface is once wet, a continuous thin film of water over the whole surface. Although this test does not indicate the presence of hydrophilic impurities, it is still a good indication that the cleaning process was satisfactory.

The conversion-chromatography (v) step with amorphous chromate comprises the application of aqueous solutions of chromium trioxide (CrC> 3) containing suitable activating agents such as fluorides. In this step, the aluminum surface is converted into an adherent and amorphous layer of light yellow to iridescent metal oxide blends. This layer will provide corrosion resistance, paint film adhesion and durability of the aluminum surface when painted.

This conversion process can be performed by dipping or spraying at room temperature (21-32 ° C) within a time period of 15 seconds to 5 minutes.

The conversion-chromatography (v) step with chromophosphate (CrPO4) comprises treating the aluminum surface with aqueous solutions of phosphoric acid (H3PO4), fluorides and appropriately balanced chromium trioxide (CrOs). The aluminum surface is converted into a thin, adherent, amorphous layer of slightly greenish iridescent color to a more intense non-iridescent green, depending on the aluminum surface alloy used.

This conversion process can be carried out by dipping or spraying at a temperature between 20 ° C and 45 ° C within a time period of 15 seconds to 5 minutes.

The demineralized water wash step (vii) is similar to the first, second and third wash steps, however, the water conductivity at this stage should not exceed 30 microsiemens (μβ). Demineralized water is understood to be a volume of water that has had all its naturally present mineral salts removed.

The drying step (viii) of the metal surface is carried out with

dry hot air at a temperature between 65 ° C and 70 ° C to eliminate all moisture present. At the end of this step, the aluminum surface is ready to receive the application of the selected coating system.

In conventional systems, paint is generally applied

over a zinc chromate conversion layer, the result of a protective chemical treatment process. The slightly yellow-iridescent to light brown conversion layer facilitates consumer identification that the metal has been previously treated. However, the conversion of aluminum chromate is formed by the

application of a solution containing chromium and its toxic derivatives on the aluminum surface. This solution could be considered effective in the past when the effects of toxic substances such as chromium and the irreparable damage to human health and the environment were unknown. Nowadays, extensive research has been carried out in the segment in order to try to find an efficient replacement for hexavalent chromium, used to form said conversion layer.

Chrome-free solutions, currently available on the market, form a colorless conversion layer invisible to the naked eye. This translucent layer significantly hinders consumer control of the aluminum chemical treatment step, since at first glance there is no difference between a metal that has no pretreatment and one that has actually been pretreated but formed a colorless conversion.

In the absence of pretreatment, the aluminum surface goes through the finishing process and it is only after approximately 12 hours after painting the paint that the metal part has not been chemically treated to prepare it for receiving the coating.

Furthermore, another disadvantage of obtaining aluminum parts without pretreatment is that, in the absence of chemical treatment, the metal surface remains conductive under the coating layer, so that electric current can flow freely between any electrodes in the surface. metal surface. In addition, corrosion in the metal that has not undergone effective chemical treatment is noticeably facilitated and the coating applied to the metal is no longer effective in the long run.

That is, to obtain aluminum parts with a colorless conversion layer and therefore without the guarantee of durability of the applied paint film for coating, with deficiencies in electrical current insulation and little or no corrosion resistance generated by the coating. Over time, it becomes an exponential detriment to the consumer.

On the other hand, it is noteworthy that obtaining aluminum parts with a conversion layer formed by applying the solution with chromium and its derivatives also has highly detrimental disadvantages, not only for the health of the person handling the material but also for marketing. corporate image, since the image of a company can be irreducibly devoid of merit and correlated to the commercialization of parts with toxic components, which in no way contribute to the sustainability of the planet.

Given the frequent problems encountered in existing techniques in the segment, it is evident that the market lacks a solution free of chromium and its toxic derivatives for the chemical treatment of an aluminum surface and its alloys, as well as that this The solution is capable of generating a first-color, visible conversion layer to assist the consumer in obtaining corrosion-resistant parts that can maintain the intended finish for an effective period. OBJECTS OF THE INVENTION The main object of the present invention is a composition

for pretreatment of an aluminum surface.

The present invention also provides a method for preparing and applying the composition on an aluminum surface.

Finally, the present invention is directed to the use and surface treated product of the composition described above. Brief Description of the Invention The objectives of the present invention are achieved by means of

a composition for pretreatment of an aluminum surface comprising:

(a) from 2% to 10% of a fluorinated inorganic acid by weight;

(b) from 2% to 10% of molybdate, titanate or zirconate of

such alkaline or alkaline earth or ammonia by weight, optionally in the form

fluoracid derivative;

c) from 0.02% to 0.2% of an oxidizing agent source in

Weight;

relative to the total weight of the composition.

Moreover, the objectives of the present invention are achieved.

by a method for preparing the composition described above, comprising the following steps:

(a) preparing solution 1 comprising dissolving the alkali earth or alkaline earth metal molybdate, titanate or zirconate or

nia, optionally in the form of fluoracid derivative;

b) preparing solution No. 2 comprising neutralizing fluorinated inorganic acid to pH 4.5;

c) preparing the final solution comprising mixing solution No. 1 with solution No. 2 and neutralizing the medium to pH

5.0 to 5.8, finally adding the oxidizing agent.

The objects of the present invention are also achieved by a method for applying said composition comprising the steps of degreasing, washing, deoxidizing, chemical treatment, washing and drying.

Finally, the objectives of the present invention may be achieved by

by the use of the composition described above for the chemical treatment of an aluminum surface, and further by a surface product treated with said composition.

The present invention has the advantage of a solution used in the chemical treatment of aluminum, prepared with a composition completely devoid of chromium and its toxic derivatives, capable of converting the aluminum surface into a brown color conversion layer which is visible to the eye, yet capable of increasing the adhesion power of the paint on the aluminum surface, and with excellent corrosion resistance, which in turn easily exceeds the current requirements of the standards governing quality of painted aluminum. Detailed Description of the Invention

The present invention describes an innovative and sustainable solution for the chemical treatment of an aluminum surface and its alloys which, in addition to having a composition free of chromium and toxic derivatives, is also capable of converting the aluminum surface into an adherent, amorphous, brown-colored conversion layer with possible variations in bluish and / or yellow tones.

In a preferred embodiment, aluminum surface pretreatment begins with the alkaline degreasing step using a product capable of dissolving and removing oils, greases and lubricants from aluminum extrusion, such as degreasing. alkaline LL- CLEAN M12 produced by the company Italtecno do Brasil Ltda®. Said product has surfactant properties capable of easily dissolving the magnesium oxide film that tends to form on the aluminum surface.

For the alkaline degreasing step to be prepared

In this case, it is necessary to fill a tank with water to ¾ of its volume and heat to a temperature between approximately 55 ° C and 75 ° C and to add the LL-CLEAN M12 alkaline degreaser in a preferred concentration between 20g / L and 60g / L. Keep stirring for a few minutes to achieve solution homogenization. Aluminum should be immersed in the tank with the homogenized mixture for a period of 1 to 3 minutes to remove all residue adhering to the aluminum surface.

The present application further provides that the initial degreasing step may optionally be carried out in an acid medium using, for example, the LL-TECNOCLEAN acid degreaser produced by Italtecno do Brasil Ltda®. This product is composed of an acidic solution of organic salts, capable of producing a slight homogeneous attack on the aluminum surface to remove oils, greases and lubricants.

The preparation of the acid degreasing step is similar to alkaline degreasing, in which the tank water is heated to a temperature of approximately 35 ° C to 55 ° C and the LL-TECNOCLEAN solution, dissolved in water, is mixed in the tank to the desired concentration (preferably 50g / L to 70g / L). The aluminum should be soaked in the tank with the homogenized mixture for the preferred period of 1 to 3 minutes. It should be noted that both in alkaline degreasing

As in acid degreasing, aluminum can also be spray-bathed. In this case, the aluminum is conveyed by conveyor belt to a kind of tunnel which sprays the previously homogenized LL-CLEAN M12 alkaline solution or spray LL-TECNOCLEAN acid solution onto the surface of the aluminum. in order to promote the removal of unwanted constituents.

It is noteworthy that all stages of aluminum pre-treatment can be performed by immersion or spray bath, and the choice of surface bath type may vary according to the type of industrial installation.

After the degreasing step is completed, the first surface cleaning of the aluminum is then performed by dipping or spraying, preferably with industrial running water, to remove excess product used in the degreasing step. The volume of water must be constantly renewed to control the level of contamination.

Then, the deoxidation step is preferably performed in an acid medium, using, for example, the product LL-DESMUT A 30 produced by Italtecno do Brasil Ltda, in order to remove the oxides on the aluminum surface. which, in turn, are undesirable for the next steps. The water in the tank is heated to a temperature of approximately 20 ° C to 25 ° C and the LL-DESMUT A 30 solution, dissolved in water, is mixed in the tank to the desired concentration (preferably 40g / L to 50g). / L). The aluminum is immersed or sprayed in the tank with the homogenized mixture for the preferred period of 1 to 3 minutes.

It is worth noting that the deoxidation step is optional when the pretreatment of aluminum is performed with acid degreaser, in which case there is no need for neutralization.

Subsequently, a second industrial running water wash is preferably performed by dipping or spraying to remove excess product used in the deoxidation step. For a better result of the surface pretreatment of the

In the case of aluminum, this request provides that a third wash, preferably with demineralized water, should be carried out immediately after the second wash. Demineralized water has the purpose and ability to remove all ions present on the aluminum surface. Having completed the above steps, the aluminum found

It is capable of receiving the aqueous solution object of the present patent application during the next chemical treatment step in order to form a color conversion layer visible to the naked eye and free of chromium from its toxic derivatives. It should be clarified that the composition of this aqueous solution

Sa is preferably prepared in three distinct steps, namely: Step One: Preparation of Solution No. 01

Hot dissolution of an alkali or alkaline earth metal molybdate, titanate or zirconate or ammonia, optionally in the form of a fluoridic derivative, in demineralized water under agitation.

In a preferred embodiment, the source of alkali or alkaline earth metal molybdate, titanate or zirconate or ammonia is chosen from the group consisting of sodium molybdate, potassium molybdate, fluoride ammonium molybdate acid, sodium fluoride molybdate acid, acid potassium fluoride molybdate, molybdic acid, hexa acid titanium fluorine, hexa acid potassium fluorite, hexa fluorine sodium titanate, hexa fluorine ammonium titanate, hexa fluorine zirconium acid, hexa fluorine potassium zirconate, hexa acid sodium fluorine zirconate and hexa acid ammonium fluorine zirconate.

This first solution has the objective of releasing ions, which, at the end of the preparation of the composition, will be responsible for the corrosion resistance of the metallic surface, as well as for the visible coloration expected at the end of the pretreatment solution application. on the aluminum surface.

Step Two: Preparation of Solution # 02

Preparation of the mixture of a fluorinated inorganic acid in demineralized water and adjusting the pH with an alkaline solution to pH 4,5. In a preferred embodiment, the alkaline solution used to adjust the pH is an ammonium hydroxide solution. At this stage, the pH of the solution should be adjusted to a slightly acidic pH, as the presence of acids can lead to conversion as they react directly with the aluminum surface. Then note the volume spent as a percentage (%). In a preferred embodiment, fluorinated inorganic acid

used is a fluoric silicic acid, hexa fluorine zirconium acid or hexa fluorine titanic acid.

In a second preferred embodiment, the fluorinated inorganic acid is a 30% fluorine silicic acid or a 45% hexa fluorine zirconium acid. These are the preferred sources of silicon and zirconium, respectively.

The use of a fluorine source has the function of reacting with the aluminum surface, since fluorine creates the necessary conditions for the formation of zirconium, silicon, molybdenum and aluminum complexes. Step Three: Preparation of the Final Solution Solutions No. 01 and No. 02 are mixed under continuous agitation.

Then, while still stirring, the medium is neutralized with an alkaline solution to pH 5.0 to 5.8. Note the volume spent as a percentage (%).

The solution obtained is cooled to room temperature and an oxidizing agent is added, leaving the final solution to stand for 12 hours to form an oxidizing medium for the reactions to complete. During this period of rest there is also the decantation of occasional solid suspended particles.

In a preferred embodiment, the alkaline solution used to adjust the pH of the solution is an ammonium hydroxide solution.

In a second preferred embodiment, the source of oxidizing agent is a hydrogen peroxide or organic peroxides. It is observed that the use of an oxidizing agent has the function of enabling the reaction that occurs on the aluminum surface, giving stability to the compound. However, deficiency or excess oxidizing agent may favor an unfavorable condition for the reaction, so that an undesired complex may be formed.

Once the three steps for the preparation of the chromium and toxic derivatives free solution disclosed in the present invention are completed, their application to an aluminum surface should be carried out according to the procedure widely known to those skilled in the art in order to fully meet the requirements of the main Brazilian technical standards of the Brazilian Association of Technical Standards - ABNT.

Preferably, the aqueous solution disclosed in the present application should be added to a tank at a concentration of approximately 45 g / l to 50 g / l and kept at a temperature of about 20 ° C to 30 ° C. For the best result of the chemical reaction, the pH of the solution should be monitored and maintained between approximately 5.0 and 6.0. Then the alumina is immersed or sprayed for 1 to 3 minutes in the final solution previously adjusted under the described operating conditions, immediately promoting the formation of a brownish brown conversion layer visible to the naked eye. , totally devoid of chromium and its toxic derivatives.

Finally, the aluminum surface is rinsed preferably with demineralized water to remove excess aqueous solution used in the chemical treatment step, and then the aluminum pretreatment is completed with the surface drying step. , with dry air at an approximate temperature of 65 ° C to 70 ° C.

The purpose of drying is to eliminate all moisture present in the

surface of the aluminum, so that the aluminum is in a suitable condition to receive the application of the selected coating (painting) process.

It is noteworthy that the aqueous solution developed by the present invention as well as its application on the aluminum surface strictly meets the parameters described in the standards related to the quality of aluminum and its painted alloys.

In this context, Brazilian standards comply with international standards such as the Quality Label for the Coating of Aluminum (AMICO) and the American Materials Manufacturing Alliance (AMMA). .

Such Brazilian standards confer the quality of the application of an organic paint film on a conversion layer formed on the aluminum surface, as follows:

ABNT NBR 14125: Surface treatment - Organic coating for architectural purposes - Requirements.

This standard specifies the requirements for organic coating for architectural purposes by painting for the surface treatment of aluminum and its alloys.

In accordance with this standard, aluminum pretreatment shall consist of one or more of the following steps: degreasing; neutralization and conversion film (consisting of chromatography / phosphochromatation or anodization). Pretreated parts should not be stored for more than 16 hours and should preferably be coated immediately after pretreatment as the risk of loss of adhesion increases over time. The storage area must be kept in good weather conditions, free from dust and dust. Handling of parts should be done with clean cloth gloves to avoid surface contamination.

Then the washing, drying and polymerization steps should be performed.

The final product must be within the thickness parameters of the organic coating; brightness; impact resistance; flexibility; adherence; wet grip; hardness to graphite; artificial weathering; natural weathering; accelerated corrosion; acetic saline mist; finishing and display.

ABNT NBR 15144: Aluminum and its alloys - Surface treatment - Organic sheet coatings for architectural purposes.

For the purposes of this standard, the base plate means a plate with a specific finish to the rolling cylinders. The tested plates must meet the requirements of organic coating; corrosion resistance by salt spray exposure; brightness; impact resistance; adherence; hardness to graphite; artificial weathering; folding; cure; surface aspect of the coating; sampling and marking.

To perform the tests, a minimum of three plates from each batch must be sampled. From each plate a specimen of minimum size 120 mm χ 120 mm shall be taken from the part of the plate determined by the manufacturer. For the acceptance of the batch, the average of the three samples is taken. If the average does not meet the value specified above, the batch should be rejected.

The solution disclosed in this patent application therefore meets

both the NBR 14125 and NBR 15144 quality parameter standards, as well as the requirements defined by the qualitative tests described in the following standards:

ABNT NBR 14901: Surface treatment of aluminum and its alloys - Determination of accelerated corrosion resistance - Machu's test of the organic coating of paints and varnishes.

This standard prescribes the method for the determination and assessment of accelerated corrosion resistance by the Machu1 test method of dry organic films applied to powder and / or liquid paint and varnish on aluminum and extruded sheet products and their alloys, pretreated superficially.

The test parameters shall comply with the following conditions:

tions:

a) NaCl: 50g / L ± g / L;

b) CH 3 COOH (glacial): 10m / L ± 1m / L;

c) H2 O (30%): 5m / L ± 1m / L; d) Temperature: 37 ° C ± 1 ° C;

e) Test time: 48h ± 0.5h.

The pH of the solution should be between 3,0 and 3,3. After 24 hours, an additional 5 mL / L of hydrogen peroxide (H20230%) should be added and the pH corrected with glacial acetic acid or caustic soda. For each test a new solution must be prepared. In the results obtained, no infiltration may exceed 0.5 mm on either side of the incision. ABNT NBR 14682: Aluminum and its alloys - surface treatment - determination of wet adhesion of coatings - pressure cooker method.

This standard specifies the pressure cooker method for

wet bonding of electrophoretic coatings and powder coatings on aluminum and its alloys.

The test shall be performed with demineralized water at 20 ° C, used as a reagent, with a maximum conductivity of 10pS. Cut specimen length 50 mm ± 5 mm and width greater than 25 mm, provided it fits within the pan body.

The test must be performed at least 1 h after polymerization. Place the water in the pressure cooker until it reaches a height of 25 ± 3 mm on the specimen to be tested. Put the lid on the pan and heat it until the steam escapes. Adjust the pressure control valve to ensure an internal pressure of 100 fluorine, ± 10 fluorine. Continue to heat for 1h from the moment the first steam escape begins. Completely remove the internal pressure from the pan, remove the specimen and allow it to cool to room temperature. Apply tape to the surface of the specimen, ensuring that no air is trapped. After 1 minute, pull the tape by hand at an angle of about 45 ° C with strong and even traction.

ABNT NBR 14622: Aluminum and its alloys - surface treatment - Determination of paint adhesion - X-cut and Q-cut method.

This standard specifies the methods for determining the adhesion of any type of paint applied to the surface of aluminum and its alloys through X-cutting and grid-cutting with one or more application layers.

Initially the thickness determination should be performed after 1h of polymerization, then select an area to determine the adhesion (as flat as possible) free of imperfections, clean and dry. Measure the paint thickness of the area where adhesion will be determined with the dry film thickness gauge at a minimum of five different locations, taking three to five individual readings at each location. The arithmetic mean of the individual readings at a measurement site is considered as the thickness of the local area. For paintings up to and including 80 μιτι, use the X-cut method or the grid-cut method. For paintings over 80 pm to 600 pm (inclusive), use the X-cut method.

The result obtained must be within the graphical parameters defined by this standard, so that the expression of the results must be analyzed according to the cut performed.

ABNT 14905: Surface treatment of aluminum and its alloys - Determination of corrosion resistance by exposure to acetic salt spray of the organic coating of paints and varnishes. This standard prescribes the method for determining and evaluating

corrosion resistance by exposure to acetic saline mist of dry organic films applied to powder and / or liquid paint and varnish on laminated sheet products and extruded profiles of aluminum and their alloys, pretreated superficially.

The test shall be performed on three specimens of aluminum or aluminum alloy extruded sheet or profile and fixed within the test chamber with rigid plastic material for 1000h. Make a cross incision (90 ° C), 1 mm wide and 100 mm long, on the specimen surface to be evaluated until it reaches the metal. The surface of the test piece to be endorsed should preferably be parallel to the horizontal flow of the mist to avoid its direct impact on the surface. Flat specimens shall be placed at angles of 15 ° C to 30 ° C with the vertical. In the case of parts with complex shapes, this positioning must be done considering the region to be evaluated.

The result obtained through the infiltration into the specimens shall not exceed 4 mm on either side of the incision and the batch result shall be classified according to the result classification table described by this standard.

It should be noted that the solution disclosed in this patent application also meets other qualitative assays described in the following normals: NBR 12610, NBR14126, NBR14127, NBR 14165, NBR 14849, NBR 14850, NBR14904 and NBR 14947. Example

The composition disclosed by the present invention may be better understood by the following non-limiting embodiment, and its advantages may be proved by the fact that they efficiently meet the above Brazilian standards.

According to the preferred but not mandatory configuration, the composition of said aqueous surface pretreatment solution of an aluminum surface is prepared in three distinct steps as described below.

Step One: Preparation of Solution # 01

In a 316L stainless steel container, 40% demineralized water was added and this volume was heated to 90 ° C. Then 5.80% ammonium molybdate was added under stirring to

total solubilization of salt.

Step Two: Preparation of Solution # 02

In a 316L stainless steel container or a polypropylene container, 20% demineralised water was added. Following, 5.20% 30% silicic fluoric acid was added under stirring for 5 minutes. Still under continuous stirring the mixture obtained was neutralized with a 1: 1 ammonium hydroxide solution until reaching pH 4.5. The volume spent was noted as a percentage (%). In the sequence, 8.45% hexa fluorine zirconium acid 45% were

stirred for 5 minutes in the flask containing the 30% homogenized fluoric silicic acid. Still under continuous agitation, the mixture obtained was neutralized with a 1: 1 ammonium hydroxide solution until reaching pH 4.5. The volume spent was noted as a percentage (%). Step Three: Preparing the Final Solution

Solution No. 01 (previously prepared) was added to the stainless steel container holding solution No. 02 (previously prepared) under continuous stirring for 10 minutes. Still under continuous stirring, the mixture of the two solutions was neutralized with 1: 1 ammonium hydroxide until the pH ranged from 5.0 to 5.8. Stirring was continued for 10 minutes and the volume spent for neutralization was noted in percent (%).

The final solution was allowed to cool to about 20 ° C to 25 ° C. Then 0.13% of 130 vol hydrogen peroxide was added. The total volume amount of 1: 1 ammonium hydroxide in percentage (%) used to perform the pH adjustment was discounted from the percentage (%) value of demineralized water required to complete 100% of final product. The final solution obtained remained at rest for 12 hours. The following shows the reactions that occur in a

Preferred embodiment of the preparation of the composition for pretreatment of an aluminum surface: 1) Reaction with ammonium molybdate (NH4) 6 Mo7024.4H20 with ammonia adjusted pH 5.0 to 6.9 and catalyzed with oxygenated water.

(NH4) 6 Mo7024 + 2AI + 6H20 ---------------------- AI2 (Mo7024) + 3H2 + 6 NH4

OH

2) Reaction with hexa fluorine zirconium acid with pH 5.0 to 6.9 adjusted with ammonia

2 [(NH4) H (F6Zr)] + 2 Al + 4H20 + ----------------- AI2 [(F6Zr) 2 (OH) 2] +2 NH4

OH + 3H2

3) Reaction with fluoric silicic acid at pH adjusted with

ammonia to pH 5.0 to 6.9

2AI + 2 [(NH4) H (Si F6)] + 4H20 ---------------------- AI2 [(Si F6) 2 (OH) 2] + 2NH4

OH + 3H2

4) Putting together the reactions, the adhesion and protective aluminum, zirconium and silicon complex will be formed, used as a conversion layer for painting, according to the reaction described below:

6AI + 14H20 + (NH4) 6 Mo7024 + 2 [(NH4) H (F6Zr)] + 2 [(NH4) H (SiF6)] ------------------- -----

AI6 (Mo7024) (F6Zr) 2 (OH) 4 (SiF6) 2 + 10 NH40H + 9H2 Once the three steps have been completed for the preparation of the

Chromium and toxic derivatives free position disclosed in the present invention, the application of the aqueous solution on an aluminum surface was carried out according to the technical procedures described by ABNT, well known to those skilled in the art. Before applying the chromium-free aqueous solution to the surface

aluminum, the conventional metal pretreatment steps were carried out under the operating conditions mentioned above throughout this application.

The previously prepared aqueous solution was added to a tank at a concentration of 45 g / l to 50 g / l, and kept at a temperature between approximately 20 ° C and 30 ° C with a pH controlled between 5.0 and 6.0. Subsequently, the aluminum was immersed in said aqueous solution for 3 minutes, so that a brownish brown conversion layer, noticeably visible to the naked eye, was immediately formed on its surface.

Finally, a new wash with demineralized water was performed and the aluminum pretreatment was completed with the surface drying step, with dry air at approximately 65 ° C to 70 ° C.

The aluminum surface was further tested as determined by the qualitative assays described in the Brazilian standards for the quality of aluminum and its painted alloys, and the efficiency of the colored conversion layer formed using the disclosed composition was proven. in the present application, completely free of chromium and its toxic derivatives, with high corrosion resistance power and completely suitable for receiving the selected coating (paint).

Having described examples of preferred embodiments, it should be understood that the scope of the present invention encompasses other possible variations, being limited only by the content of the appended claims, including the possible equivalents thereof.

Claims (14)

1. Composition for the pretreatment of an aluminum surface, characterized in that it is an aqueous solution composed of the following components: (a) from 2% to 10% of a fluorinated inorganic acid by weight; (b) from 2% to 10% alkali or alkaline earth metal molybdate, titanate or zirconate or ammonia by weight, optionally in the form of a fluoracid derivative; c) from 0.02% to 0.2% of a source of oxidizing agent by weight; relative to the total weight of the composition. Composition according to Claim 1, characterized in that the fluorinated inorganic acid is fluorine silicic acid, hexa fluorine zirconium acid or hexa fluorine titanic acid. Composition according to Claim 1, characterized in that the alkali or alkaline earth metal molybdate, titanate or zirconate or ammonia are chosen from the group consisting of sodium molybdate, potassium molybdate, ammonium fluoride acid molybdate. , sodium fluoride acid molybdate, potassium fluoride acid molybdate, molybdic acid, hexa fluoride titanic acid, hexa fluoride potassium titanate, hexa fluoride sodium tita- nate, hexa fluorine ammonium titanate acid, hexa fluorine zirconium acid, acid potassium hexa fluorine zirconate, sodium hexa fluorine zirconate acid and ammonium hexa fluorine zirconate acid. Composition according to Claim 1, characterized in that the oxidizing agent is hydrogen peroxide or organic peroxides. Composition according to Claim 1, characterized in that it comprises demineralized water. Method for preparing the composition as defined in any one of claims 1 to 5, characterized in that it comprises the steps of: a) preparing solution No. 1 comprising dissolving the molybdate, titanate or zirconate of alkaline or alkaline earth metal or ammonia, optionally in the form of a fluoracid derivative; b) preparing solution No. 2 comprising neutralizing fluorinated inorganic acid to pH 4.5; c) preparing the final solution comprising mixing solution No. 1 with solution No. 2 and neutralizing the medium to pH 5.0 to 5.8 and finally adding the oxidizing agent. Method according to claim 6, characterized in that in step (a) the alkali or alkaline earth metal molybdate, titanate or zirconate or ammonia is dissolved in demineralized water. Method according to claim 6, characterized in that in steps (b) and (c) the neutralization for pH adjustment is carried out with ammonium hydroxide solution. Method for applying the composition as defined in any one of claims 1 to 5, characterized in that it comprises the steps of degreasing, washing, deoxidizing, chemical treatment, washing and drying. Method according to claim 9, characterized in that the composition is applied during the chemical treatment step. Method according to Claim 9, characterized in that, at all stages, the aluminum surface is bathed by dipping or spraying. Use of a composition as defined in any one of claims 1 to 5, characterized in that it is for the chemical treatment of an aluminum surface. Product characterized in that its surface is treated with the composition as defined in any one of claims 1 to 5. An invention, in any form of its embodiments or in any applicable category of claim, for example, of product or method or use encompassed by the subject matter initially disclosed, disclosed or illustrated in the patent application.