DE1621441A1 - Process for the corrosion protection of metals or metal alloys - Google Patents

Description

Process for the corrosion protection of metals or metal alloys .

The invention relates to a method for protecting metals or metal alloys from corrosion and / or for producing them a primer for painting or plastic deposition by applying an essentially organic one Plating using electricity.

Numerous methods are known to protect metals or metal alloys from corrosive influences by an essentially organic coating, usually a lacquer or plastic coating, is applied. Such a Coating can also be used as a primer for a particular decorative painting or plastic deposition are used. Starting from mechanical application methods are more recent Time procedures have been developed that take the deposition on effect electrochemical V / ege (electrophoretic painting; anodic or cathodic plastic deposition). For the Various proposals for solutions have been made to the specific problems encountered in this connection (see e.g. English patent specification T 05Q 172).

The previous 1 "invention" stands as a result of the creation of a in the common sense of organic tibersjugo, it is true with the pre-atonous

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outlined procedure in a certain technological context. However, it is not intended to separate Synthetic resins or plastics. The process for the corrosion protection of metals or metal alloys and / or for their production a primer for a paint or plastic deposition by applying an essentially organic coating using electricity is characterized in that connected to the anode or cathode Metals or metal alloys in an aqueous bath containing one or more surfactants coating consisting of surfactant is applied.

Preferably, the surfactant consists of substantially coating is post-treated in the heat, with temperatures ranging from 80 to 200 ⁰ C are appropriate.

Electrochemical deposition is particularly suitable are ionogenic, i.e. H. anion-active or cation-active surfactants. Suitable surfactants are

a) anion-active: fatty acid condensation products,

Salts of alkyl sulfosuccinates,

Salts of castor oil sulfuric acid half-esters (Turkish red oils),

Alkyl sulfates, alkyl phosphates, Alkyl sulfonates, alkyl aryl sulfonates,

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b) cation-active: alkyl pyridinium salts,

Alkylammonium salts,

c) nonionic: polyoxyalkylene adducts.

The surfactant concentration is preferably in the range from 1 to 100 g / l.

The pH value is preferably 3 - 14. In the case of iron, is it is expediently above 8, in the case of aluminum, magnesium or their alloys in the range of 6-14.

For the formation of the water-insoluble coating you can be responsible for different reactions.

The surfactant can be connected to the anodically or cathodically metallic objects form insoluble compounds.

The formation of the insoluble coating can also be achieved by the Heat treatment (stoving process) can be brought about.

Finally, an insoluble layer can be created by using cation-active and anion-active surfactants one after the other to be deposited. In this case, the deposition can take place cathodically and anodically or vice versa. But it can also the 1st surfactant is deposited cathodically or anodically on the metal or metal alloy and the 2nd oppositely charged surfactant by a chemical, d. H. electroless aftertreatment can be applied and thereby the insoluble Form connection.

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The electrochemical coating is carried out with direct current, with alternating current or with superimposed direct current. The voltages required for the deposition are generally between 2 and 250 volts, in certain exceptional cases up to 600 volts. The initial current density is set in the range between 0.05 and 20 A / dm ² , in exceptional cases up to 80 A / dm ² . The deposition time is usually between 2 and 60 seconds.

For an even layer formation, it is advisable to to move the bath liquid or the objects to be treated.

The bath to be used in the process according to the invention is retained preferably the addition of a complexing agent, the complex ions with the dissolving metal ions able to form. It has also proven to be useful to add the bath to suppress the oxygen resp. Hydrogen formation on the objects to be coated add suitable compounds. In the case of anodic coating formation, these are oxygen acceptors, e.g. B. hydrazine, or in the cathodic coating formation hydrogen acceptors, such as. B. peroxide.

In the production of: coatings on aluminum, magnesium or their alloys, the sodium salt of Hzinus oil sulfuric acid ester (Turkish red oil) has proven to be an anionic surfactant and as a cationic surfactant, octadecyloxymethylene

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pyridinium chloride proved to be particularly useful. Of the Addition of fluoride, such as potassium fluoride, uni the setting to a pH in the range from 6 to 14 leads to a further improved embodiment. .

The process according to the invention gives the possibility, together with the surfactants, of subordinate amounts of low molecular weight or high-molecular substances with organic, organometallic or inorganic structure. Examples these include oils, fats, waxes, plastics and pigments. This process variant is possible because the Surfactants have a very good wetting power for foreign substances, keep them in suspension and cause them to migrate force within an electric field.

In the cathodic or anodic coating formation of Metals or metal alloys can generate a lot of heat, which has an influence on their appearance and density of the coating. The appearance of a layer with a paint-like appearance can, for. Legs Be a consequence of the heat development.

By adding leveling agents and / or softeners, organic, organometallic or inorganic compounds the smoothness of the layer can be increased

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The method according to the invention makes it possible to produce coatings with high corrosion resistance. In addition, ask

The coatings are an excellent primer for paints or

z. B. plastics are, according to conventional procedures, / on.

mechanical or electrochemical means applied can be. ■

The examples explain the process according to the invention. Execution examples

Sheets with the dimensions 100 100 χ 1 mm were used for the tests. They consisted of iron with $ 0.05> carbon or aluminum of quality 99.7 (soft).

For the pretreatment for the electrochemical coating with surfactants, the sheets were first placed in a bath Composition

15 g / l sodium hydroxide,
5 g / l sodium carbonate,
5 g / l sodium yanide,

Have water

cathodically degreased. The process data for the cathodic Degreasing goods:

Voltage 10 volts

Current density 8 A / dm ²

Degreasing time 60 seconds

BATH ORIGINAL bath temperature 20 C

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Bath volume 2 1 counter electrode (anode) V2A.

Following the degreasing, the sheets were washed with water washed. '

The electrochemical coating with T enside was carried out under the conditions given in the table.Example 1 illustrates the anodic coating of aluminum with the sodium salt of the castor oil sulfuric acid half-ester (Turkish red oil), an anionic surfactant.Example 2 shows the anodic deposition of a higher alkyl phosphoric acid ester of an anionic surfactant on iron again. The bath also contains hydrazine as an oxygen acceptor

Example 5 contains the cathodic deposition of a cationic fatty acid condensation product on iron. ■. "■ ■

Example 4 illustrates the coating of iron. An aqueous bath is used which contains a condensation product of polyoxyethylene and polyoxypropylene as a nonionic lensid. The bath also has an addition of hydrazine as an oxygen acceptor. Example 5 shows the lenside deposition on aluminum in two stages. In the X. Stage the anion-active disodium octadecylsulfosuccinate is deposited anodically. In the following 2nd stage, the cathodic deposition of octadecyloxymethylene pyridinium chloride takes place,

a cationic surfactant.

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Example 6 describes a two-stage coating, in the first stage the anion-active Disodium octadecyl sulfosuceinate is deposited using electricity. In the 2nd stage happens then electroless treatment with a bath containing the kationalctive octadecyloxymethylene pyridinium chloride contains. .

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aluminum A. ) 5 9 8 20/1 933 2 ± D = Tabel iron 4 ^ Is. aluminum Examples Type of coatingϊanodic 6-8, iron E B cathodic iron aluminum anodic Coating dated C? En & id anion active anodic P a C. anodic anodic / cath. E + F B. D. 1 «Level E ! i'2n3idtyp 50 Q = fatty acid condensation product kationakt. 2 level P anlonaktiY E BAD ORIGINAL f Q anionakti "? not" anion active B cationic 1 ! Partial concentration 6g / l K ₂ F ₂ 50 ionogenic cation active P 50 φ 100 (ia g / 1) 50 50 2 χ 50 Basic kits 8 + 2 18g / l 18g / l 12,000 Hydrazine Hydrasin pH maintenance of the bath 15-40 2g / l HaOH 6 + 1 2g / l SaOH 7 + 1 '■ ■ Conductivity of ?) 50 12 + 2 12 _e 000 12 ^ 1 , 7 ^ 1 12..000 ! Temperature of
Baths (in ° C) 8th 15c000 15-20 13o000 12,000 15 - 40 Working voltage (in 15-40 50 15 - 40 15-40 E »50 | ϊ β ο Initial current density
(in Α / άη ² ) 5 25th 5 100 2 χ 50 It 5 ° ϊ s'o Duration of occupation 5 1 5 (in see) Stoving temperature (in ⁰ C) 120 10 • Ö "" ^ * ü Ä ° «· ^ y Burn-in time (generally min 15th 5 3 ■ '. , Shift achieved
you (in / u)
■ / 160 160 A = Turkish red oil 160 10 160 160 10 B = alkyl phosphate 10 5-6 10 io ■■ 6-8 3 - 5 2 -3 8-10. Polyoxyethylene-polyoxypropylene adduct Disodium octadecyl sulfosuccinate Octydecyloxymethylene pyridinium chloride

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In the experiments described, layers were created

the haftfestg formed evenly and closed

and which have excellent corrosion protection.

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Claims (2)

~ n ~ 1B.2H41 patent claims 1) Method gum Korroaionsschuts von Metallen © egg metal alloys and / or for the production of a primer for a paint or plastic separation by applying an essentially organic coating using electricity, characterized in that "metals or metal alloys in a coating consisting essentially of Teneid is applied to an aqueous bath containing one or more surfactants « 2) Method according to claim I ₅ , characterized in that the coating consisting essentially of! Densid is treated in the heat » 5) The method of claim 2 _{9 0} characterized in that the after-treatment at temperatures in the range * i? Made on 80 ^"0 to 200 G", 4) Method according spoke 1 _f, characterized in that the coating in an aqueous containing one or more ionogenic surfactants. Bath is applied. 5) Method according to claim 1 and 4 _P, characterized in that the aqueous bath Teaeiö contains in amounts of 1 to 100 g / l «, 109820/1933 BATH - 12 - 1621UI 6) Method according to claim 1, 4 or 5, characterized in that that the coating in two stages by treatment with a cationic surfactant and then by treatment with an anion-active surfactant is produced 7) Method according to claim 1, 4 or 5, characterized in that that the coating in two stages by treatment with an anionic surfactant and then by treatment with a cationic surfactant is generated. 8) Method according to claim 6 or 7, characterized in that that the treatment in the 2nd stage is carried out without current. 9) Method according to claim 1, 4, 5 _t 6 or 7, characterized in that a complexing agent is added to the aqueous bath. 10) Method according to claim 1, 4, 5 »6, 7 or 9» thereby characterized in that when anodic coating is formed, an oxygen acceptor is added to the aqueous bath. 11) Method according to claim 1, 4, 5, 6, 7, 8 or 9, characterized characterized in that a hydrogen acceptor is added to the aqueous bath when a cathodic coating is formed. 12) Method according to claim 1 to 11, characterized in that that when applying coatings to aluminum, magnesium 109820/1933 16-2 KAI or their alloys, the deposition from one of the sodium salt of castor oil or sulfuric acid ester An aqueous bath containing octadecyloxymethylene pyridinium chloride is made 13) Method according to claim 12, characterized in that Potassium fluoride is added to the aqueous bath and the pH is adjusted to 6-14. Prankfurt (Main), DrOz / BWi 109.8 20/193 3 . BATH ORIGINAL