DD281427A5 - CORROSION-REDUCING SUBSTANCES - Google Patents

Abstract

As corrosion-reducing substances for the protection of metallic surfaces, especially iron surfaces, against corrosion, which have no adverse side effects compared to other known substances for this purpose, monomeric and / or polymeric chelating compounds have been found. These compounds are, in particular, phthalocyanine, tetraarylporphyrin and tetraazaanulen and similar substances characterized by general formulas.

Description

Field of application of the invention

The present invention relates to substances which protect metal articles, especially those made of iron materials, from corrosion for a long time and which are organic chelate systems.

Characteristic of the known state of the art

Metallic articles can be protected from corrosion by coating them with an organic, inorganic or metallic protective layer. In particular, the organic protective layers are to increase their «. Corrosion protection usually provided with special pigments and / or fillers. Conventional pigments and fillers for this purpose are mostly inorganic in nature, such as red lead, zinc chromate, zinc phosphate, talc, graphite, mica, etc. In recent years, organic compounds have been used as anticorrosive pigments alone or in combination with inorganic pigments and / or fillers , Such organic compounds are for. B. benzidine phosphate, benzidine molybdate, Benzidinhexacyanoferrat, organic phosphonic and arsonic acids and aromatic and aliphatic carboxylic acids and their salts, vie Benzoate and Laureate.

Where a solid coating in the manner described is not possible or desired, the medium surrounding the metal, such as aqueous solutions of chemical substances, non-aqueous solutions or pure chemical media, eg. As lubricants, or the surrounding gas space special organic cder inorganic substances added, which act as inhibitors or passivators. There are numerous publications and patents on these inhibitors and passivators that describe the use of these substances. Preferably, these are the following connection classes:

Amines, e.g. Cyclohexylamine, dicyclohexylamine, diethylamine, aniline, pyridine, imidazoline, piperidine, octadecylamine, ethanolamine, morpholine, quinoline, urea.

Carboxylic acids, e.g. Adipic acid, lanolin acid, stearic acid, phthalic acid, benzoic acid.

Aromatic nitro, nitroso, cyano compounds, e.g. Nitrophthalic anhydride, nitrobenzene, m-dinitrobenzene, a-nitronaphthalene, nitrosobenzene, p-nitroso-N, N-dimethylaniline, cyanobenzene, tolunitrile.

- Phosphonium compounds, for. B. Tetraphenylphosphoniumsalze, methyl triphenylphosphonium salts, Bunzylphosphoniumsalze.

Sulfur compounds, e.g. Thiourea, ethyl trithiocarbonate, mercaptobenzothiazole, alkyl dithiophosphoric acid ester.

- Organometallic compounds, eg. B. zinc bis (2-ethylhexyl) dithiophosphate.

Chelating organic compounds have also been described for corrosion protection, e.g. Tannins, a-nitroso-ß-naphthol, etc.

The disadvantage of many of the common inorganic and organic additives is their toxicity, eg. As zinc chromate, and / or justified in their unfavorable influence on the environment, such. B. Amines. Furthermore, the inorganic additives in particular impair the usability of overweldable primers formulated therewith or preclude their use as overweldable primers.

So far, it is common practice to eliminate these disadvantages of the additives mentioned in organic coatings or corrosive media by completely avoiding these additives or replaced by other materials that do not have these negative properties. In each of these cases, formulation of environmentally friendly organic coating materials or the action of corrosive media without such specified special passivating or inhibiting additives means a more or less drastic reduction in the corrosion protection sought.

Object of the invention

The aim of the invention is to completely or largely avoid the adverse side effects.

Explanation of the essence of the invention

The object of the invention is to specify substances which, with the same or improved corrosion-protective action, do not cause any negative side-effects during their use.

It has been found that monomeric and / or polymeric, metal-containing or metal-free, chelating compounds capable of catalyzing the oxygen reduction on the metal surface greatly reduce the corrosion of metals, preferably iron and iron alloys, by passivation of the metal surface. Such chelating substances are those corresponding to the general formulas

T A-

correspond. In this case, A / B are aromatic or cycloaliphatic radicals which may also contain heteroatoms such as S, Se, O, N, and additional substituents such as aryl, alkyl, halogen, oxygen, sulfur or nitrogen-containing groups, R ₁ to R ₄ Η atoms odf r alkyl radicals. In the metal-containing form, iron, nickel, cobalt, manganese, chromium, copper, bismuth, tin or zinc may preferably be present. Particularly suitable compounds of the mentioned chelating, oxygen reduction-catalyzing substances are phthalocyanines, porphyrins and tetraazaanulenes. The chelating substances can be applied to the surfaces alone in a suitable manner or used as additives to organic, inorganic or metallic protective layers, such as, for example, As clearcoats and pigmented paints also in aqueous form. It is also an additive to other, preferably liquid, corrosive media or media surrounding the metal, such. As lubricants, hydraulic fluids, mineral oils or polymeric corrosion inhibitors possible. The use in gaseous media is also possible. Likewise, in given cases, a combination of the erfir.dungsgemäßen substances with known inhibitors, passivators, electrochemically active and chemically inert pigments and / or fillers, such as. As talc, calcite, kaolin, etc., take place. As an effective additional amount up to 20Ma .-%, preferably 10 to 20Ma .-%, have been recognized.

Exemplary embodiments (the data are given in% by mass)

example 1

PC concentrate (15%)

Alkyd resin solution (60% in xylene)

tricresyl

Solvent mixture (toluene, xylene, butyl acetate)

boiled linseed oil

iron phthalocyanine

41.0 9.0 3.0 23.0 4.0 20.0

100.0

This paint was applied with a dry film thickness of 25μπι on the metallically pure surface of mild steel sheets. After complete drying, the coated sheets were subjected to various tests: measurement of the electrical potential and the concentration of the dissolved iron with continuous immersion in aqueous 0.5 η K ₂ SO ₄ solution, measurement of the increase in resistance of steel foils under SO ₂ action (modified Kesternich). Test), evaluation of the condensation test and the natural weathering.

In comparison with paints of the same type but containing other conventional inorganic anti-corrosive pigments instead of the iron phthalocyanine, equivalent or better results were obtained.

Example 2 45.0 Alkyd resin (50% in xylene) 16.5 Hard resin (50% in white spirit) 17.0 Solvent mixture (white spirit, solvent benzene) 0.7 Skin contraceptives 0.6 Bleisikkativ 0.2 Kobaltsikkativ 20.0 Nickelphthalocyanln

100.0

The tests of Anstrichas were carried out in the same manner as described in Example 1. The result was better than corresponding comparative coatings with conventional inorganic anti-corrosive pigments.

Example 3

PC concentrate (15%) 41.0

Alkyd resin solution (60% in xylene) 9.0

Tricresyl phosphate 3.0

Solvent mixture (toluene, xylene, butyl acetate) 23.0

Linseed oil siren 4,0

Calcite 10.0

Iron phthalocyani 10.0

ΤΟυ, 5 "

The test of the paint analogously to Example 1 gave better results than in comparison paints with a mixture of conventional fillers and inorganic anti-corrosive pigments in the same mixing ratio.

Example 4

PC concentrate (15%) 41.0

Alkyd resin solution (60% in xylene) 9.0

Tricresyl phosphate 3.0

Solvent mixture (toluene, xylene, butyl acetate) 23.0

Linseed oil siren 4,0

Cobalt tetraphenylporphyrin 2C, 0

100.0 The test of the paint analogously to Example 1 gave better results than in comparison paints.

Example 5

Dimethylformamide 75.0

Water 10.9

Borate buffer, pH 6.7 14.0

Iron phthalocyanine 0.1

100.0

The current potential behavior of iron electrodes in the solution according to Example 5 was determined and a decrease in the iron dissolution ratio was found, which corresponds to a 97% reduction in corrosion (Diagram 1).

Diagram 1 to Example 5

I f Γ

loo

Iron ptitialocyanine in DMP / borate

DMP / borate pH 6.7 4 3: 1

20

ι I 1 Γ

-feoo -2.00 2.00 boo 1ooo U

Table 1

Test results for the paints according to the invention and analogous comparative paints a: paints according to the invention according to Examples 1 to 4

b: Analogous coatings with conventional anti-corrosive pigments

Test pigment 1 pm 2 degrees rust / month 3 grate grad 4 mV (SCE) 5 "Ο 6 pm a) iron phthalocyanine 35 0/22 0 -100 74 25 a) Nickel phthalocyanine 31 0/22 0 -140 72 26 a) iron phthalocyanine + calcite 39 0/22 0 -230 82 28 a) cobalt tetraphenylporphyrin 42 0/21 0 -190 79 23 b) red lead 36 0/22 0 -220 66 30 b) zinc chromate 80 0/20 0 -360 173 31 t) zinc phosphate 66 0/18 0 -310 145 29

Test 1: Modified Kesternich test

The corrosion erosion in pm at SO ₂ stress was measured by resistance measurements on coated iron foils

determined. The value obtained after 25 weeks test period is indicated. The SOj concentration was C, 67% by volume. Test 2: condensation test

The Humidity test was performed as a continuous load with steam at 4O ⁰ C. Test 3: Outsourcing

The outsourcing took place on a weathering stand in big city atmosphere. Test4: Resting potential

The resting potential of coated iron electrodes in 0.5 η K ₂ SO ₄ solution was measured and the set value

indicated on the 100th day of immersion

Test 5: The dissolved iron amount became after immersion of coated steel sheets of 7cm ² area in aqueous 0.5n

K ₂ SO ₄ solution after 100 days using the phenanthroline-iron complex determined and measured spectroscopically. Test 6: Thickness of the coating on the test panels used.

Claims (1)

Erfir. JL, f "Appeals: I. Corrosive substances for the protection of metallic surfaces, in particular of fi ls; > ". ksioffen, against corrosion, characterized by monomeric and / or polymeric metal-free or metal-containing, chelating compounds corresponding to the general formulas I and II * u in which A / B are aromatic or cycloaliphatic radicals which also contain heteroatoms such as S, Se, O and N, and additional substituents such as aryl, alkyl, halogen, oxygen, sulfur or nitrogen-containing groups R ₁ to R _{4 may be} Η-atoms or alkyl radicals and optionally Me = Fe, Ni, Co, Mn, Cr, Bi, Sn or Zn. Corrosion-reducing substances according to Claim 1, characterized in that they are a monomeric and / or polymeric metal-free or metal-containing phthalocyanine, tetraarylporphyrin or tetraazaculene.