ITMI20090665A1 - PROCESS OF TREATMENT IN CONTINUOUS PATINATURA / SATINATIMATE CHEMICA OF ZINCO-TITANIUM ALLOYS - Google Patents

Description

Description of the patent for industrial invention entitled:

â € œCONTINUOUS TREATMENT PROCESS OF COATING / CHEMICAL SATIN FINISH OF ZINC-TITANIUM ALLOYSâ €

The present invention relates to a continuous treatment process of chemical patination / satin finishing of zinc-titanium alloys used for building applications, in particular for roofs, facades, gutters, interiors or for architectural works.

State of the art

The laminates of zinc-titanium alloys are widely used in construction, in particular for roofing and cladding. The natural appearance of these coatings can be varied thanks to particular surface treatments of pre-glazing.

These processes must exclusively confer on the coil surface, having a chemical composition in compliance with the requirements of the EN 988 - 1998 standard (see table 1), a pleasant aesthetic appearance, with a patinated effect, a specific chromatism, such as antiqued zinc, excellent antifinger properties and a remarkable resistance to corrosion.

Table 1

Element Standard EN 988 - 1998

Al <0.0150%

Cu 0.0800 Ã1.0000%

Pb <0.0030%

Cd <0.0030%

Fe <0.0020%

Sn <0.0010%

Ti 0.0600 Ã 0.2000%

The known process normally consists of the following phases:

- degreasing with alkaline liquid degreaser in aqueous solution - washing with renewal water

- acid treatment of chemical patination / satin finishing with specific products

- second wash with renewal water

- final passivation treatment

- drying of the wet film.

EP 827785 describes a process for the treatment of zinc-titanium laminates characterized by the use of a nitric and sulfuric acid-based pickling bath and a passivation step with a chromate-containing polymer.

Description of the invention

An improved process has now been found characterized, after the second washing with water, by a pre-passivation phase, which is followed by drying with hot air, to avoid the formation of superficial zinc oxides, and by the use , in the final passivation treatment, of a polyacrylic resin as an antifinger agent.

The process of the invention includes in particular the following phases: - degreasing;

- wash;

- acid treatment of chemical patination / satin finishing;

- second wash;

- pre-passivation treatment with a chromium-free bath containing zirconium and / or titanium and aluminum compounds;

- air drying;

- passivation treatment comprising a first treatment phase with a conventional inorganic component based on chromium 3 and / or 6 or chromium-free and a second treatment phase with an antifinger agent consisting of an aqueous solution of an acrylic resin consisting of monomers based on butylacrylate, methylmethacrylate and acrylic acid, having the following characteristics: pH <6 - PM â ‰ ¥ 250000 - TG (glass transition) between 30 and 45 ° C - dry residue between 30 and 50%, possibly in a mixture with corrosion inhibitors such as zinc oxide and P2O5:

- drying of the wet film.

Degreasing, as known, is used to eliminate all traces of oils, greases, cleaning paste, oxides and any other impurities from the coil surface, in order to have a perfectly clean metal surface for subsequent treatments.

Normally, this degreasing is carried out with liquid products in aqueous solution with an alkaline pH (10 Ã · 14). The use concentration is between 1% and 10%, the working bath temperature between 50 ° C and 70 ° C, for a treatment time between 5 and 40 seconds, with spray pressures between 1 and 4 bar. The main elements of the degreasing bath are listed in the following table 2.

Table 2

Concentration element

KOH or NaOH 2 - 20 g / l

P2O52 - 20 g / l

Surfactants 200 - 3000 ppm Sequestering additives 1 - 10 g / l

P2O5 is present either as orthophosphates (monosodium, disodium, trisodium phosphate) or as polyphosphates (tripolyphosphate or neutral pyrophosphate), all in the form of sodium or potassium salts.

The most used surfactants are ethoxylated fatty alcohols with C9-C11, C12-C13 or C12-C 18 alcohol chain at different degrees of ethoxylation, or containing different numbers of moles of ethylene oxide.

The sequestering additives are organic compounds selected from nitriloacetic acid, sodium gluconate, gluconic acid, disodium ethylenediaminetetraacetic acid, trisodium ethylenediaminetetraacetic acid, phosphonates, acrylates, polyacrylates.

The first wash with renewal water is used to eliminate all traces of the previous phase; the temperature is normally between 30 ° C and 60 ° C, with times ranging from 5 to 30 seconds, and the application is by spray.

The chemical patination / satin finishing treatment takes place by pickling the Zinc-Titanium alloy with a surface attack between

5 and 20 g / m <2>.

Normally, the treatment is done with a specific product a

pH between 0 and 2, used in concentrations between 10 and 15%. There

working bath temperature can be between 50 ° C and 70 ° C for a

reaction time between 10 and 30 seconds, the pressure of the spray

it can be between 1 and 4 bar.

The main elements of the coating / satin bath are listed

in the following table 3:

Table 3

Element Concentration H2SO410-150 g / l Surfactants 1 - 15 g / l Process accelerator such as NO3100 - 6000 ppm Sequestering agents 1 -100 g / l Elements deriving from the attack of the alloy

Zn <100 g / l

Other metals from the alloy <100 mg / l

The process accelerator can consist of

NO3, such as, for example, nitric acid, ammonium nitrate, nickel nitrate, sodium

nitrate, zinc nitrate, iron nitrate, cobalt nitrate or organic compounds

nitrogenous such as nitroguanidine, used alone or mixed with each other. THE

surfactants and agents are the same as those already described above.

The second wash with renewal water is carried out as in the case

of the first wash, to eliminate all traces of the previous phase; there

temperature is normally between 30 ° C and 60 ° C, with varying times

from 5 to 30 seconds, and the application is by spray.

Pre-passivation, which prevents the formation of surface zinc oxides by increasing the anticorrosive properties of the coil, is carried out by treatment with a chromium-free bath containing zirconium and / or titanium and aluminum compounds.

The typical composition of a pre-passivation bath according to the invention is shown in the following table 4. The concentration of the product ranges from 1 to 5%, the temperature from 30 to 60 ° C, the treatment times from 1 to 10 seconds ; the application can be by spray or by immersion, the pH value is <5.

Table 4

Concentration element

Zr 100 - 5000 mg / l

Ti 100 - 5000 mg / l

At 10 - 500 mg / l

NH3100 - 1000 ppm

The zirconium compounds are preferably selected from fluozirconic acid, ammonium zirconium carbonate, potassium fluozirconate; the aluminum compounds are selected from aluminum oxide of various extraction (aluminas), aluminum fluoride, aluminum bifluoride; the titanium compounds are selected from fluotitanic acid, titanium oxalate, titanium oxide, potassium fluotitanate.

The drying is then carried out with hot air from 50 to 90 ° C.

Final passivation treatment

The application of the antifinger passivating product is carried out with a Chem-Coater type machine in two distinct application phases interspersed with a wet film drying step.

In the first phase, the inorganic component is applied which, depending on the desired process, is of three different types:

â € œChromium 3 - Chromium 6 versionâ € (Version 1)

The product consists of chromic acid, chromium phosphate, corrosion inhibitors such as zinc phosphate and zinc chromate and reducing agents such as gluconic acid, citric acid, sucrose, hydroxylamine, methanol, hydrogen peroxide, starch. The application takes place at a temperature between 15 ° C and 40 ° C, continuously; the concentration of use depends on the wet film applied, which varies between 2 and 10 ml / m <2> and is generally between 10 and 50%, so that the final result is a total chromium deposit of 20 at 100 mg / m <2>; its value is calculated from the mg of chromium taking into account that 1 mg / m <2> of Cr = 16 mg / m <2> of total coating.

The exemplary composition of the bath is shown in the following table 5.

Table 5

Element Concentration Total chromium (= chromium 3 chromium 6) 5 - 20%

P2O51 - 5%

Zinc 2 - 8% â € œChromium 3 Versionâ € (Version 2)

The product consists of phosphoric acid, chromium phosphate, chromium nitrate, complexing agents selected from salified or acid phosphonates, gluconic acid, citric acid, tartaric acid, EDTA, glycolic acid and / or polyacrylates, corrosion inhibitors such as colloidal silicas in suspension, with possible different particle sizes, generally lower than 30 µm and with a SiO2 content between 10 and 50%, as well as, finally, organic wetting agents based on alkoxy polypropoxy polyethoxy-ethyl-benzylether or belonging to the family of perfluoro derivatives. The application takes place at a temperature between 15 ° C and 40 ° C, continuously; the concentration of use depends on the wet film applied, which varies between 2 and 10 ml / m <2> and is generally between 30 and 70%, so that the final result is a total chromium deposit of 30 at 80 mg / m <2>; its value is calculated from the mg of chromium taking into account that 1 mg / m <2> of Cr = 32 mg / m <2> of total coating).

The exemplary composition of the bath is shown in the following table 6.

Table 6

Concentration element

Total chromium (= chromium 3) 20 - 200 g / l

P2O510-150 g / l

NO33 - 50 g / l

SiO220 -200 g / l

â € œChromium-free version - chromium â € (Version 3)

The product consists of silanes, selected from the families of 1-propylamine, 3- (triethoxysilyl) -silane and trimethoxy [3- (oxiranylmethoxy) -propyl] -silane, titanium salts deriving from fluotitanic acid, titanium oxalate, oxide of titanium or potassium fluotitanate, alkaline phosphates such as monobasic or dibasic ammonium phosphate, mono, bi or tribasic sodium phosphate, acid or neutral potassium pyrophosphate, alkaline nitrates such as ammonium nitrate, sodium nitrate, potassium nitrate, sequestrants selected from nitrile acetic acid, sodium gluconate , gluconic acid, disodium ethylenediaminetetraacetic acid, trisodium ethylenediaminetetraacetic acid, phosphonates, acrylates, polyacrylates, and corrosion inhibitors based on heavy metals such as vanadium, molybdenum, tungsten, cerium. The product must be applied at room temperature, in concentrations ranging from 80 to 100% so that the titanium deposit is between 4 and 8 mg / m <2> and that of SiO2 between 70 and 140 mg / m <2> ; its value is calculated from mg of titanium taking into account that 1 mg / m <2> of Ti = 160 mg / m <2> of total coating).

The exemplary composition of the bath is shown in the following table 7.

Table 7

Concentration element

SiO210 - 150 g / l

P2O510-150 g / l

V â ‰ ¤ 100 ppm

Ti â ‰ ¤ 200 ppm

The drying is then carried out with hot air from 50 to 90 ° C.

In the second phase, an aqueous solution of corrosion inhibitors such as zinc oxide and P2O5 and an acrylic resin consisting of monomers based on butyl acrylate, methyl methacrylate and acrylic acid, having the following characteristics, is applied as an antifinger agent:

pH <6 - PM â ‰ ¥ 250000 - TG (glass transition) between 30 and 45 ° C - dry residue between 30 and 50%.

Only in the case of version 1 the application of the passivating product

antifinger can also be carried out, with a Chem-Coater type machine, in

a single phase, preparing the bath, according to the final chromium deposit

desired, or by dosing 1 part of the inorganic component and 2 parts of the

organic component, or 1 part of the first and 3 parts of the second. There

amount of mixture is applied from 2 to 6 ml / m <2>. During this phase we have

a partial reduction of Chromium from 6 to 3.

The wet film is then dried at a web temperature from

80 to 140 ° C.

Method of conducting laboratory tests

Degreasing:

Element Concentration KOH 4 g / l P2O5 from neutral potassium pyrophosphate 5 g / l C9-C11 chain surfactants 5 and 6 moles of OE 500 ppm Sodium gluconate 3 g / l

Concentration of use of the product 3 ÷ 5% Temperature 50 ÷ 60 ° C Treatment time 10â € Spray pressure 2 bar

First wash

Demineralized water for renewal -Temperature 30 ° C Treatment time 10â € Spray pressure 2 bar

Chemical patination / satin finishing:

Concentration element

H2SO460 g / l HNO36 g / l C9-C11 chain surfactants 5 and 6 moles of OE 1500 ppm

Sodium gluconate 10 g / l

Concentration of use of the product 10%

Temperature 60 ÷ 70 ° C

Treatment time 10â €

Spray pressure 2 bar

Second wash

Demineralized water for renewal -

Temperature 30 ° C

Treatment time 10â €

Spray pressure 2 bar

Prepassivation

Concentration element

Zr (from fluozirconic acid) 500 mg / l

Ti (from fluotitanic acid) 300 mg / l

Al (from alumina) 50 mg / l

NH350 ppm

Concentration of use of the product 2 ÷ 3% Temperature 50 ° C

Treatment time 2â €

pH 4

Drying is typically carried out with one hot air

temperature between 60 and 80 ° C.

Final passivation

First phase: â € œChromium 3 - Chromium 6 versionâ €

Element Concentration Total chromium (= chromium 6 chromium 3) 13%

P2O53%

Zinc 3%

Reducer used starch

Wet film applied 1 - 4 ml / m <2> Room temperature

First phase: â € œChromium 3 versionâ €

Element Concentration Total chromium (= chromium 3) 40 g / l

P2O520 g / l

NO35 g / l

SiO240 g / l

Complexing agent used Citric acid Type of silica used Grain size 15 µm - dry 30% Type of wetting agent perfluoro-derived Wet film applied 1 - 4 ml / m <2> Ambient temperature

First phase: â € œChromium-free versionâ €

Element Concentration SiO2 (from 1-propylamine, 3- (triethoxysilyl) -silane

and / or trimethoxy [3- (oxiranylmethoxy) propyl] -silane <100 g / l> P2O5 (from monobasic ammonium phosphate) 20 g / l V 100 ppm Ti (from fluotitanic acid) 200 ppm Complexing agent used phosphonate Nitrate used ammonium nitrate Type of inhibitor chosen vanadium Room temperature

Drying is typically carried out with one hot air

temperature between 60 and 80 ° C.

Second phase: all versions.

Used resin <Pure acrylic, newly formulated, inhibited,> with dry residue = 30%, pH = 4, TG = 32 ° CFapplied wet film 3 - 6 ml / m <2>

Application in a single phase: â € œChromium 3 - Chromium 6 versionâ €

Inorganic component 1 part -Organic component 2 parts Dosage ratios

Inorganic component 1 part - Organic component 3 parts

Wet film applied 3 - 4 ml / m <2>

Room temperature

Drying can be done with hot air at one temperature

between 100 and 120 ° C.

Examples

Laboratory tests were performed in order to compare i

results obtained with cycles that did not include the pre-passivation phase

(conventional cycle) with others, in all similar to the previous ones, but which, al

on the contrary, they included this phase, with relative subsequent drying.

In the cycles relating to the â € œChromium 3 - Chromium 6 versionâ € they have been tested

both the application in two phases of the final passivating product and that in a single phase; in the latter case, dosage ratios have been tested

of the two components equal, respectively, to 1: 2 and 1: 3.

In the cycles relating to the â € œchromium-free versionâ € both were tested

the silanes listed above, identified below with the letters,

Î ± and β, respectively, alone and in combination.

In all cycles it was used, in the organic component of the phase

final passivation, only the acrylic resin according to the invention.

For convenience, table 8 below shows the mode with

which the various cycles tested have been distinguished.

Table 8

Pre-passivation code Passivation version Ratio Type of silane component passivation dosing A 1 No 1 Biphasic

A 1.2 No 1 Monophasic 2: 1

A 1.3 No 1 Monophasic 3: 1

A 2 No 2 Biphasic

A 3.1 No 3 Biphasic Î ± A 3.2 No 3 Biphasic β A 3.3 No 3 Biphasic Î ± β B 1 Yes 1 Biphasic

B 1.2 Yes 1 Monophasic 2: 1

B 1.3 Yes 1 Monophasic 3: 1

B 2 Yes 2 Biphasic

B 3.1 Yes 3 Biphasic Î ± B 3.2 Yes 3 Biphasic β B 3.3 Yes 3 Biphasic Î ± β

After the application of the cycles, the zinc-titanium alloy sheets are treated

have been subjected to corrosion resistance test in a fog chamber

salina, in compliance with the ASTM B117 Standard, verifying on panels such

which and with protected edges the appearance of the first white oxides.

Table 9 reports the results obtained which are expressed as hours of

exposure elapsed before the appearance of the first oxidation phenomena

white.

Table 9

Initials Hours of Initials Hours of exposure exposure

A 1 72 B 1 96

A 1.2 72 B 1.2 96

A 1.3 72 B 1.3 96

A 2 60 B 2 72

A 3.1 60 B 3.1 72

A 3.2 60 B 3.2 72

A 3.3 72 B.3.3 96

Claims (8)

CLAIMS 1. A continuous treatment process of patination / chemical satin finishing of zinc-titanium alloys comprising the following phases: - degreasing with alkaline liquid degreaser in aqueous solution; - wash; - acid treatment of chemical patination / satin finishing; - second washes; - pre-passivation treatment with a chromium-free bath containing zirconium and / or titanium and aluminum compounds; - air drying; - passivation treatment comprising a first treatment phase with a conventional inorganic component based on chromium 3 and / or 6 or chromium-free and a second treatment phase with an antifinger agent consisting of an aqueous solution of an acrylic resin consisting of monomers based on butylacrylate, methylmethacrylate and acrylic acid, having the following characteristics: pH <6 - PM â ‰ ¥ 250000; TG (glass transition) between 30 and 45 ° C; dry residue between 30 and 50%; optionally mixed with corrosion inhibitors such as zinc oxide and P2O5; - drying of the wet film. 2. A process according to claim 1 in which the zirconium and / or titanium and aluminum compounds in the pre-passivation bath are selected from fluozirconic acid, ammonium zirconium carbonate, potassium fluozirconate; aluminum oxide of various extraction (aluminas), aluminum fluoride, aluminum bifluoride; fluotitanic acid, titanium oxalate, titanium oxide, potassium fluotitanate. A process according to claim 1 or 2 wherein the passivation comprises a treatment with a bath comprising chromium 3 and chromium 6 compounds. 4. A process according to claim 3 wherein the bath comprises chromic acid, chromium phosphate, zinc phosphate and zinc chromate and reducing agents. A process according to claim 1 or 2 wherein the passivation comprises a treatment with a bath comprising chromium 3 compounds. 6. A process according to claim 5 wherein the bath comprises phosphoric acid, chromium phosphate, chromium nitrate, complexing agents, corrosion inhibitors and organic wetting agents based on alkoxy polypropoxy polyethoxy ethylbenzylether or belonging to the family of perfluoro derivatives. A process according to claim 1 or 2 wherein the passivation comprises a treatment with a chromium-free bath. 8. A process according to claim 7 wherein the bath comprises silanes, selected from the families of 1-propylamine, 3- (triethoxysilyl) -silane and trimethoxy [3- (oxiranylmethoxy) propyl] -silane, titanium salts deriving from fluotitanic acid , titanium oxalate, titanium oxide or potassium fluotitanate, alkaline phosphates, alkaline nitrates, sequestrants selected from nitrilacetic acid, sodium gluconate, gluconic acid, disodium ethylenediaminetetraacetic acid, trisodium ethylenediaminetetraacetic acid, phosphonates, acrylates, polyacrylates and corrosion inhibitors, base of heavy metals selected from vanadium, molybdenum, tungsten, cerium.