JPH0320480A - Surface oxidation treatment of aluminum - Google Patents

Abstract

PURPOSE: To develop adhesive members for metals having excellent strength of adhesion by treating Al thin sheets with a fluid compsn. contg. specific ratios of H₂O₂ and H₂SO₄ to form porous oxidized films and applying adhesive on their surfaces.

CONSTITUTION: The surfaces of the Al thin sheets are treated with the fluid compsn. contg. <8% H₂O₂ and <20wt.% H₂SO₄ and contg. metal ions, such as Cu²⁺, at a liquid temp. of 65 to 90°C from 4 seconds to 10 minutes by methods, such as spraying treatment, immersion treatment and roll coating. Both surfaces of the Al thin sheets are oxidized by these treatments and the porous oxidized films having the many fine holes are formed at 100 to 1000Å thickness similar to the anodically oxidized films of Al. The paint, lacquer or the org. adhesives are applied on the oxidized film surfaces. The treatments are effectively utilized in the non-rinsing treatment of the Al thin sheets and are usable effectively for the adhesion of the metals as the powerfully adhesive media by the adhesives, etc., entering the micropores of the oxidized films.

COPYRIGHT: (C)1991,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates primarily (but not exclusively) to the use of peroxidation in the surface treatment of aluminum to prepare the aluminum for applications in which the aluminum is to be bonded using thermoset polymeric adhesives. Concerning the use of hydrogen. Using such an etching mixture, A,
C. It has not been previously known that a filamentated porous structure, somewhat similar in thickness and morphology to that produced by anodizing, appears on aluminum surfaces. This structural organization is non-1≧ due to adhesive bonding.
: This is suitable, and the adhesive has pores 111 in the oxide structure.
- Penetrates deeply and hardens therein, creating a strong anchoring effect of the polymer (this is manifested in the high tensile strength of the resulting bond). The combination of hydrogen peroxide and mineral acids gives the metal such a porous surface and results in similarly high tensile strength of the adhesive joint when joined with a one-part epoxy adhesive. It is well known that

For example, Bijlmer 7- (Bijlmer) is 1976
In a paper presented at ``Interfinish 76: Procession Ninth World Congress ●On◆Metal Finishing'' held in Amsterdam in 2017, the delamination of adhesively bonded aluminum pieces in relation to the microscopic roughness of the metal surface was presented. Discloses strength results. Similarly, JP-A-53-97037 describes the use of peroxide pretreatment to provide a highly adhesive fluoropolymer coating on aluminum. Special Public Service No. 52-813937
Similar descriptions are also made in JP-A No. 53-132035.

The technical background of the invention, as mentioned above, is the increasing use of aluminum in adhesively structurally bonded applications. applications where adhesive joints are subjected to significant tensile and shear loads, and in many cases where adhesive joints must be durable even when exposed to adverse conditions of temperature and humidity. This is due to the increased use of aluminum in Yoikawa.

: Such an application of IJ Ming is in aircraft construction.
i is the use of minium, and since ancient times it has been a kind of yang}j
acid (gb) to prepare the surface for adhesive bonding.
It has been recognized that it is appropriate for However, anodizing finishes have been viewed by the aircraft industry as unsuitable for coil-state processing on T-luminium, and are therefore a pretreatment that can be carried out in rapid coil state. One that provides good durability is highly desirable, especially if no chromium is used.

Similarly, oxidative treatments using peroxides have low processing speeds, e.g., 10 minutes and 30
It is shown that a processing time of minutes was used. There is a need for a processing method of this type that is sufficiently rapid to be carried out on aluminum coil material.

A clear distinction needs to be made between peroxide treatments designed to form an oxide layer on aluminum and peroxide cleaning treatments. Peroxide cleaning mixtures (typically from Nippon Bariki Rising Ltd. UK Patent No. 2200138) are often used on aluminum and copper. Oxide solubilizers such as fluorides are always included in these formulations, and the purpose of the treatment is to remove the naturally occurring oxide layer, not to form anything in its place. . Such peroxide cleaning mixtures provide metal with surfaces that exhibit poor adhesive bonding. In a paper on the bondability of peroxide-cleaned metals, Venables and co-workers confirmed that peroxide pretreatment produced a strong initial bond, but aluminum in a humid environment Due to the known instability of oxides, it is doubtful that durable bonds will be produced from aluminum (Dicek, Breen and Venables, 'Martin Marietta Institute Report MML-TR-80-17cJ;'1980
(April).

The need for adhesive bonds to be durable in harsh environments has led to the development of no-rinse coatings on aluminum surfaces. Such a coating may consist of a solution of hexavalent and trivalent chromium compounds mixed with submicron particulate silica, as described in US Pat. No. 3,708,803. This type of commercially available non-rinse treatment agent has the trademark R
There is one by Accomet CJ. The recommended pretreatment consists of rinsing with acid or alkali to remove the naturally occurring oxide layer from the aluminum surface and provide a clean bare metal surface for the attachment of a no-rinse coating.

E P A 34040 describes the application of a solution containing a peroxide and a metal salt to an aluminum metal surface to form a conversion coating containing the metal (in chemically bound form) on the aluminum surface. is listed. To achieve a uniform conversion coating, the peroxide concentration is preferably 2.
Maintained below 0g71.

Preferably, a fluoride is included to prevent the formation of aluminum oxide.

C H 540350 describes a chemical process for forming aluminum oxide coatings on aluminum metal. The treatment solution preferably contains fluoride. Peroxide solutions can be used. Alternatively, alkaline solutions containing heavy metals for introduction into the coating can also be used. The process takes 20-30 minutes.

In one embodiment, the present invention provides for applying a fluid composition comprising a Bell compound to an aluminum surface under conditions that cause the formation of an artificially deposited oxide layer, and applying an inorganic coating to the top surface of the oxide layer. Provided is a method comprising the steps of: In another embodiment, the invention comprises applying a fluid composition comprising at least 30 g/l of a Bell compound to an aluminum surface under conditions that cause the formation of an artificially deposited oxide layer. A method,
The above method is characterized in that the fluid composition includes an effective concentration of metal ions that promotes the formation of an artificially deposited oxide layer.

The term "aluminum" herein includes pure aluminum metal and alloys thereof. The Bell compound may be an organic peroxide such as a peracid such as peracetic acid, but is preferably hydrogen peroxide.

Salts such as KHSO can also be used, but are considered very expensive sources of H2025. Because of the naturally occurring oxide layer on the aluminum surface, these per compounds cannot form an artificially deposited oxide layer on their own, but by removing such naturally occurring oxide layer and depositing the per compound on the aluminum. to form the desired artificially deposited oxide layer (
It is necessary to generate <) without significantly redissolving it. The use of mineral acids, e.g. sulfuric acid, is preferred for this purpose as it gives a mechanically stronger oxide film and therefore a stronger adhesive bond, whereas the use of alkalis, e.g. sodium hydroxide, is preferable since aluminum is reactive in significant concentrations. This is possible if the alloy does not contain eg lithium or magnesium.

Suitable metal ions are in particular those of transition metals such as Cu. Care must be taken to ensure that the Bell compound is sufficiently stable in the presence of the selected metal ion at the required concentration. It is believed that these metal ions form a bimetallic cell with the aluminum metal substrate, which anchors the formation of the artificial oxide layer.

The metal ions should be at a sufficient concentration to facilitate the entire treatment process (ie, including the removal of naturally occurring oxides and the formation of an artificially deposited oxide layer on the aluminum surface). The metal ion concentration must not be so high as to rapidly decompose hydrogen peroxide or other Bell compounds. It is also important that the metal ion concentration is not so high that the metal precipitates (plats) and deposits on the aluminum surface in a manner that accelerates corrosion. In practice, it is not difficult to select a metal ion concentration that meets these requirements. Fluid compositions containing 0.05-5%, especially 0.1-1.0%, soluble gold salts will provide suitable metal ion concentrations.

The fluid composition may include an amine at a concentration that promotes the formation of an artificially deposited oxide layer. It is believed that such amines can increase the effectiveness of copper salts, possibly through the formation of copper amine complexes. Ammonia is suitable if its volatility can be controlled. Preferred amines are dimethylethanolamine and triethanolamine. Preferred concentrations are 0.5-5% (by weight), especially 1-3% (by weight). The use of amines is advantageous when low reactivity Al alloys are being processed, such as 6000 series alloys such as 6009 and 6111.

Peroxide treatment conditions may be those described in the aforementioned references. The hydrogen peroxide concentration is preferably high so as to maintain stability and shorten the treatment time as much as possible. We have obtained good results using 8% (V/W) H202. Higher concentrations are not readily available;
I don't think it gives any advantage. H202 concentrations below 3% (V/W) can be used under suitable conditions, but tend to give flatter, less contoured oxide films.

The acid (or alkali) concentration needs to be sufficient to dissolve the naturally occurring oxide film, but not so high as to dissolve the artificially deposited oxide layer;
Concentrations of sulfuric acid below 0% polymerization may be suitable. Some H 2 O 2 stabilizers contain sulfuric acid (see below), so this needs to be taken into account when considering the overall acid concentration.

We have performed successful experiments using only the acid present in the H202 stabilizer (i.e., good results were obtained using only 0.6% H2SO4 overall). Acid concentrations above 10% can increase the rate of oxide dissolution at elevated temperatures. The preferred overall acid concentration is 1-10% by weight.

Processing temperatures can be ambient or elevated, depending on the stability of the Bell compound. If hydrogen peroxide is used, the preferred temperature is in the range 50-90°C.

Generally, the peroxide water table is 50 to 50% to avoid rapid decomposition.
It is believed that it should be used at a temperature of 65°C. However, hydrogen peroxide is heated at 65-90℃ in the presence of stabilizers.
Temperatures higher than 75°C to 85°C are preferred. The use of such higher temperatures may allow for shorter processing times or may result in greater bond strength for the same processing time.

Treatment times of 4 seconds to 10 minutes are preferred, although shorter times are appropriate for higher temperatures and more concentrated solutions (particularly for spray application methods).

Optimal processing times are often in the range of 4-80 seconds. For continuous coil coating processes, 4-30 seconds may be preferred. Batch operations may require 15-60 seconds. Excessively long treatment times may begin to degrade the resulting contoured oxide layer. These processing times allow continuous processing of aluminum coils, sheets or extrudates.

The fluid composition can be applied to the metal surface by dipping, roll coating or other application methods.

However, for the coil treatment method, the preferred application method is the spray method. The spray method promotes the reaction between the composition and the metal. Pre-cleaning of the aluminum metal surface is possible, but is only considered necessary if the surface has a relatively thick native oxide film (for example, if the aluminum coil has been annealed). It is an important advantage of the present invention that a pre-cleaning step of the aluminum metal surface can be avoided not only at high processing temperatures of 65-90°C, but also at conventional peroxide processing temperatures.

After treatment, rinse the aluminum metal surface.
need to be done. Unexpectedly, the rinsing temperature had a negative effect on performance. A thousand influences. Above ambient temperature, e.g. 50~
A rinse temperature of 90°C is preferred for the process of this invention.

Stabilizers can be added to the mixture to extend its life; a saturated solution of a proprietary stabilizer sold by Interox under the trademark rstabtabsJ has been found useful. If rapid production of highly reticulated and filamentated oxide surface textures is important, activators can be used; an example of a useful activator is 1% (V/V) Sodium thiosulfate.

Another effective stabilizer is an alcohol or a glycol such as propylene glycol. Patented stabilizer r B 222 sold by Interlock.
J is believed to be a mixture of glycol and acid.

Patented stabilizers r B 33J, r B 104J and r
B 222J allows the use of hydrogen peroxide solutions at high temperatures such as 90°C above 65°C.

Fluoride must not be present in the mixture; it will dissolve the oxide structure as it is forming.

Depending on the process of the invention, typically 100 to 100
An artificially deposited oxide layer with a thickness of 0 angstroms is provided. By appropriate selection of the acid (or alkali) concentration and treatment temperature, such an artificially deposited oxide layer is made to have a profiled surface with fine oxide protrusions or whiskers. Therefore, mechanical interlocking by the whisker reinforcement of the adhesive appears to serve to enhance the adhesive bond. Scanning electron microscopy of the contour oxide layer shows porosity typically on the scale of 50 to 100 na+ The artificially deposited oxide layer is then deposited with an organic coating such as a varnish, lacquer or adhesive. It makes an excellent base for. under humid, corrosive or other adverse conditions;
To achieve an adhesive bond with improved durability,
It may be preferable to further deposit another coating on the surface of the oxide layer to prevent hydration of the oxide layer.

One preferred method is to deposit an inorganic coating on the surface of the artificially deposited oxide layer. The inorganic coating is preferably a no-rinse coating, preferably a pre-formed or in-situ formed inorganic particle-containing coating. The inorganic coating is preferably thin enough that the contoured surface morphology of the artificially deposited oxide layer is substantially maintained. The artificially deposited oxide layer provides improved initial adhesion for the subsequently applied organic film by mechanical interlocking,
And it is believed that the inorganic coating applied by this process ensures that the initial good adhesion is not reduced by prolonged exposure to high humidity or corrosive environments.

The non-rinse coating may consist of a hydrous metal oxide sol of the type described in EP A 35g338. Since the artificially deposited oxide layer has the desired profile, there is no need to include passenger powder in the sol to change the surface morphology, although such powders can be added if desired. An example of such a powder is fumed ◆ silica.
i I R 202J (trademark of Degassa).

Dissolved adhesion promoters may also be applied in the no-rinse composition or separately before or after the sol. If the composition is intended for no-rinse treatment, it is preferred that the ingredients be substantially non-toxic. Bacteria promote adhesion, e.g. by providing a suitable link to the underlying oxide layer and to the overlying organic layer, or by preventing corrosion at the organic coating/oxide layer/metal interface. do. Prevention of such corrosion helps maintain adhesive bond strength.

The adhesion promoter may consist of a phosphate or a phosphonate. Phosphate esters are known to bond well to aluminum surfaces and may inhibit corrosion. Besides phosphoric acid and inorganic phosphates, there are a number of organic phosphorus-containing compounds that can be used, examples being aminophosphates such as nitrilotris(methylene)phosphonic acid (NTMP) or other nitrilo-substituted phosphonic acids, or bis( and phosphate esters such as nonylphenyl ethylene oxide) phosphate.

The adhesion promoter is one or more organosilanes,
For example, it may consist of glycidoxypropyltrimethoxysilane or aminopropyltriethoxysilane. The compositions of the present invention may include one or more of these or other dissolved adhesion promoting and/or corrosion inhibiting ingredients, such as molypdate, zirco aluminate, organo-aluminate, etc. There are also metal trivalent chromium compounds and hexavalent chromium compounds.

After peroxide treatment, r A eeolet C J
Chromium-based non-rinse coatings such as chromium-based non-rinse coatings can be used, but are not particularly preferred. When the underlying oxide coating is profiled, it is based on very fine particle size material that enters the pores of the oxide layer.
Advantageously, a non-rinsing coating is used so that its contoured surface can be seen through. Oxide layers formed by peroxide treatments may not adhere reliably to the underlying aluminum metal when used with other non-rinse coatings, such as chromium-free non-toxic coatings. , would be advantageous.

Another method involves applying to the oxide layer a compound which decomposes under the action of heat and/or moisture to form an inorganic coating. Preferred examples of coatings of this type are titanate esters and chelates which form titanium dioxide coatings upon the action of heat and moisture. Commercially available substances of this kind are thai oxide●
Trademark rT11coa+P from International Company
I 2 J, rTilcom AT31J and rTi
Supplied by lcom PBTJ. These are titanate esters and chelates which decompose under the action of heat and moisture to give hard and stable titanium dioxide coatings. A useful coating will range in thickness from 0.01 to 0.1 micron over the artificially deposited oxide layer.

The no-rinse composition is applied to the metal surface (having an artificially deposited oxide layer with a contoured surface) by any suitable method such as spin coating, dipping, flow or roller coating or spraying. For aluminum coil material, roller coating would be one example of a useful method. The formulation needs to be adjusted to provide the appropriate viscosity for application by the desired method. After application, the coating on the metal surface is allowed to dry, but rinsing is usually not required. Drying temperatures are typically up to 200°C.

The metal surface with the artificially deposited oxide layer has a thickness of 0.005 to 0.
5g/rf, preferably 0.01-0.1g/rrl'
It is preferable to have a coating within the range of .

The present invention involves applying a fluid mixture containing a Bell compound and an inorganic coating (e.g., non-rinse) coating component to an aluminum metal surface to form an oxide layer on the metal surface and an inorganic coating thereon. It is also intended within its scope to carry out the two steps simultaneously.

The present invention is of interest to the use of adhesively bonded aluminum parts as automotive structures where it is also intended, as an additional step, to apply an organic coating such as a paint, lacquer, varnish or adhesive to the protective coating. It is increasing.

An example of a commercially available adhesive suitable for this application is rP
ermabond ESP105J (trademark).

Hereinafter, the present invention will be illustrated and explained with reference to Examples.

Two non-resist coating compositions were used in these examples. One is Albright &Wilson's patented chromium-containing pretreatment agent R Accomet C.
J, and the other one was a chromium-free pretreated material rJT10J having the following composition.

3% (v/v) phosphoric acid 190g Fumed alumina (Degassa) llsr fumed silica (Aeros11 380. Degassa) 33g Water
80sr These ingredients are mixed and dispersed with a "Silverson" or other high shear stirrer to form a stable homogeneous dispersion.

Example 1 Hydrogen peroxide 6% (w/v) sulfur
A piece of 5251-HO aluminum with a thickness of 0.7-1 was heated at 60 °C in a mixture containing 15% W haυ (hereinafter referred to as "solution I").
Processed for 0 seconds. Also solution I + rstabtabs
It was also treated in a saturated solution of A. J (Solution ■) or in Solution I (Solution ■) with the addition of 10 g/l of sodium thiosulfate. For comparison, r Ridoline 124
A 2% solution of /l20E J (solution ■) was also used. This is a commercially available (ICI) sulfuric acid/HF/wetting agent mixture and is a common acid detergent.

All of the above treatment agent aluminum pieces were coated with about 100 g/rri" rJTIOJ using a roll coater and dried at 150°C. The thus pretreated aluminum pieces were cut into a size of 20 mm x 100 mm. The material was bent into an L-shaped bond and bonded with a standard thermoset, single-part structural epoxy adhesive to create a T-shaped joint with a 60 inch long adhesive layer.

These were tested using an Instron 15J tensile tester.
Peeling was performed at lm/min and the steady state peel load was recorded during this peel. The results were as follows.

I 77,78.80 65I
I 72.74.75 57
m 70-. 77.80 7
0IV 3B. 39.42 The thickness of the porous structure was measured by scanning microscopy (SEM) with the following results.

I 370 angstroms ■ 480 angstroms ■ 560 angstroms Example 2 Solution ■ was used at various times and temperatures. The test piece is marked with “A
ccomet C J was coated at a constant coverage of 15 .mu./n-il'. In this example, only the dry peel load was measured. The results were as follows.

Etching conditions Peeling load (N) 40°C, 30 seconds 25, 27. 2440℃
, 120 seconds 45. 44. 4860℃, 3
0 seconds 58, 54. 5560℃, 12
0 seconds? 5, 69. It can be seen that the initial strength of the 73 adhesive joint is very high. However, processing times longer than 30 seconds are required to achieve the highest bond strength.

Example 3 To avoid uneconomical line lengths, coil material pretreatment speeds require metal contact times of no more than about 20 seconds. A sheet of 0.7a+m5251-H2O aluminum was treated for 20 seconds at 60<0>C in a mixture of the following composition.

Hydrogen peroxide 6% (w/v) sulfur
Acid: 15% (w) Hereinafter, this will be referred to as solution I. Similarly, another aluminum sheet was added to the above solution with a solution (solution V) in which 1% (V/ν) of copper sulfate hexahydrate was added. Processed.

Cut these pretreated aluminum sheets into 20mm pieces.
Take a piece of Xl00mm, fold it to form an L-shaped bonded material, and glue it with a standard thermosetting one-component structural epoxy adhesive to create a T-shaped joint with an adhesive layer of 60ma+ length. made. These were peeled at 5 mm/min on an Instron 1115 tensile tester and the steady state peel load was recorded during this peel. The following results were obtained.

from 82N (complete cohesive failure location within the adhesive and no failure at the interface)
This is a significant improvement.

Example 4 The experimental conditions used in this example were similar to Example 3, but
Different stabilizers were present in the peroxide compositions and different standard heat cure one-part structural epoxy adhesives were used.

The results were as follows.

Solution Low speed peel strength (N) I 4B, 53. 53 (average 51)
V50. 57. 66 (average 58)
The addition of copper ions to the peroxide composition resulted in a low peel strength in the range of 20 N in this test (Complete Example 5). This shows that the storage stability in warm and humid environments is improved.

A sheet of 0.7 mm 5251-HO aluminum,
Treated in a mixture containing hydrogen peroxide (6% w/v) and sulfuric acid (15% w/w) at 60°C for 60 seconds, rinsed with deionized water and dried at 100°C for 3 minutes.

It was then roll coated to a dry thickness of 0.01 to 0.1 micron with the coating described below.

l. Alkanolamine titanate chelate in water}AT
1% (w/w) solution of 31; dried at 300°C for 1 minute.

2. Fumed silica Arosi] R 20
2, a 20% (w/v) dispersion of glycidoxypropyltrimethoxysilane, and a 20% (w/w) solution of ethoxyethanol (all in deionized water). Mixture = Dry at 200°C for 3 minutes.

AT31 is commercially available from Tioxidc International Ltd., Cleveland, UK, and is available from Acrosi
1R202 is commercially available from Degassa, Wilmslow, Cheshire, UK.

The resulting samples were cut into test pieces, and these test pieces were kept at 25°C and 98% R.C. in a humid cabinet. II. The specimens were artificially aged for a period of time, then bonded for peel testing with a one-part structural epoxy adhesive, cured at 190°C, and subjected to slow peel testing under the conditions of Example 3. The results were as follows.

O week 2 weeks 4 weeks Peel strength retention rate (N) (%) (%> Uncoated oxide 81 73.90 70.
86 oxide +1 99 79.80 oxide +2 107 98.91 110.10
3 Example 6 This example demonstrates the use of additionally deposited inorganic coatings on top of the artificially deposited oxide layer to improve storage stability. The experimental conditions were similar to Example 5, but a coating of two titanate esters or chelates was applied after treatment to artificially deposit an oxide layer on the aluminum sheet.

These are thioxides (T i
oxide) International Inc., trademark rT11
com P I 2J and r Tilcom P B
It is sold at TJ. The applied coating decomposed under the action of heat and moisture into a hard and stable titanium dioxide coating. These thicknesses are generally 0.01-(1.1
It was within the micron range. The obtained sample was used in Example 3.
A low-speed peel test was conducted under these conditions, and the following results were obtained.

TilcomPBT is polybutyl titanate, T
iIcon+ P I 2 is ethoxyisoproboxytitanium bisacetylacetonate.

Coating Initial low speed ♂ 11 peel Peel strength after 2 weeks storage (N) Strength retention rate (%) T11coa+ PL2 77
79Tilcom PBT 67
gB Example 7 Treatment temperature The treatment solution was 8% H2S04, 6% H2O2,
It contained 1% CuSO4.5H2013% stabilizer. 0.7+am 5251-H2O aluminum sheets were treated at various temperatures for 20 seconds. Adhesive joints were made as in Example 3 and subjected to slow peel testing under wet conditions, which is a more severe test than under dry conditions. The results were as follows.

Example 8 Salt Spray Test Treatment solution was 4% ISO 6% H202, 24
Contains 3% propylene glycol. A sheet of 16B beaten 5754Aρ alloy was pickled and heated at 80°C with the above solution.
It was treated for 20 seconds.

Lap shear joints were made and heated at 43°C in a 5% neutral salt spray.
It was held at The changes in bonding strength over time were as follows.

40℃ 60℃ 80℃ B33 42 70 129
Bl04 56 78 13
Zero slow peel strength is an indirect measure of the surface morphology of the artificially deposited oxide layer. The results are better at higher temperatures.

Week 0 8 20, joint strength (M
Pa) 29.9 25.4 24.9 Example
9 The amine treatment solution consisted of 4.6% HSO, 6% H202, 24% brobylene glycol, 0.1% Cu
So 4●5 H 2 0 - contained 2% amine. A 1 mm sheet of 6009 alloy was treated with the above solution for 30 seconds at 80° C. without any pre-cleaning. A joint was made and tested as in Example 7 with the following results.

Amine Wet peel strength (average; N) None
83 Dimethylethanolamine 109 Triethanolamine 98 Morpholine 90 Example 10 Rinse temperature treatment solution was 4% H2SO4, 6% H202, 3%
8222 stabilizer. 1 mm 5754H
A 40Aρ alloy sheet was treated with the above solution at 80° C. for 20 seconds without pre-cleaning treatment. The sheets were then rinsed with deionized water at various temperatures and dried (100°C or 180°C; drying temperature is not a requirement). Joints were made and tested as in the previous example with the following results.

Rinse temperature Dry peel strength (℃) (Average.N) 2077 5077 8092 Example 1l In this example, the following two processing solutions were used.

A: 4.6%H2SO4; 6%H202;2.
4% Probylene Glycol B: 4.8% H2SO4; 6% H202; 2.4%
Propylene glycol; 0.1% CuSO4●5H20 1a+m(7) 5754AN alloy sheets were treated at various temperatures for 30 seconds and then rinsed with deionized water at the same temperature as the respective treatment mix. In some cases, the sheets were pickled for 60 seconds before processing. Bonds were made and tested as in Example 7 with the following results.

Temperature wet peel strength solution for treatment and pickling With (Y)/Without (N) (℃) (Average; N) A Y 60 42A
N 60 51A N 8
0 53A Y 80 49
8 N 60 111B N
80 120B Y 80
50 Example 12 A sheet of 5754-HOA1 alloy with an inorganic coating of 1.8 n+m was subjected to one of the following two treatments.

(1) Pickling for 60 seconds (Ridolene 12
4/l20E) L, then A ccon+et C
processed under recommended conditions.

(2) 4% HS0, 6% H 0 , 0.1
2 4 2 2 2% CuS0 5H2013% 8222 composition 4 treatment solution for 30 seconds at 80°C, rinsed at 80°C and then 0.3% (as described in EPA 358338) of zirconia and 1.5% glycidoxypropyltrimethoxysilane was applied.

Storage of pretreated metal such as Example 5 for 8 weeks gave the following strengths after the stored metal was used to make a 20 mm x 10 mm overlap single lap joint.

O week 8 weeks (1) 28.8 26. IMPa(2)
29.0 28. lMPa This means that
The coated peroxide pretreatments have been shown to have good stability, in contrast to the instability of the uncoated peroxide treatments noted by Venables in the prior literature.

When the above pretreated metals were used to make lap joints without prior storage, the joints retained their strength in salt spray (5% NaC,Q) exposure to the extent described below. (Unit: MPa) Week 0 28.0 29. O 8 weeks 23.8 23.8 20 weeks 21.2 20.7 This shows the durability of these in the test used in Example 8.

(4 other people)

Claims (13)

[Claims] 1. A method comprising applying a fluid composition containing at least 30 g/l of a Bell compound to an aluminum surface under conditions that cause the formation of an artificially deposited oxide layer on the surface, the method comprising: The above method, characterized in that the fluid composition contains an effective concentration of metal ions that promotes the formation of an artificially deposited oxide layer. 2. The method of claim 1 including the additional step of depositing an inorganic coating on top of the oxide layer. 3. A method comprising applying a fluid composition comprising a Bell compound to an aluminum surface under conditions that cause the formation of an artificially deposited oxide layer, and depositing an inorganic coating on top of the oxide layer. . 4. It consists of applying a fluid composition containing a Bell compound to an aluminum surface under conditions that cause the formation of an artificially deposited oxide layer on the surface, wherein the fluid composition is A method characterized in that it is used at a temperature of °C. 5. 5. A method according to claim 4, wherein the fluid composition is used at a temperature of 75-85<0>C. 6. 6. A method according to any of claims 1 to 5, wherein the fluid composition is applied to an aluminum surface that has not undergone pre-cleaning. 7. 7. A method according to any of claims 3 to 6, wherein the fluid composition comprises an effective concentration of metal ions that promotes the formation of an artificially deposited oxide layer. 8. The method according to any one of claims 1, 2 and 4 to 7, wherein the metal ion is Cu^+^+. 9. At least 30 g of Bell compound in the form of a solution in mineral acid
Claims 1 to 8 are hydrogen peroxide applied at a concentration of /l.
The method described in any of the above. 10. 2. The artificially deposited oxide layer has a contoured surface, and the inorganic coating is so thin that the contoured surface is visible through it.
10. The method according to any one of 1 to 9. 11. 11. A method according to any preceding claim, wherein the fluid composition comprises an amine at a concentration effective to promote the formation of an artificially deposited oxide layer. 12. Claims 1-1 comprising the additional step of applying an adhesive to the artificially deposited oxide layer or overlay inorganic coating.
11. The method according to any one of 11. 13. 11. A method according to claim 10, wherein the inorganic coating is formed by application of a hydrous metal oxide sol.