DE29505945U1 - Liquid or powdery rust converter and rust inhibitor - Google Patents

Description

Description

Liquid or powdered rust converter and rust inhibitor

The invention relates to corrosion protection, namely to compositions intended for the chemical treatment of metal surfaces having a rust layer and can be used to prepare rusty metal surfaces before painting.

This rust converter has an increased conversion capacity, protects the metal (all types of steel and iron) from further corrosion, is ecologically harmless, non-toxic and does not require pre-cleaning of the rusty metal surfaces before painting.

The rust converter can be successfully used in shipbuilding and ship repair plants (especially in the covered spaces - below deck spaces), motor transport, repair and machine building plants (especially in the hard-to-reach places of the

metal structures), in the chemical, agricultural, construction (especially in building structures), bridge building and in the household.

The fundamental difference between the rust converter offered and others is that it completely stops the corrosion process and does not slow it down or mask it, as is the case when using other types of rust converters.

This eliminates the most labor-intensive and environmentally harmful process of mechanical surface treatment, which cannot be carried out at all in hard-to-reach places and, in places where it is possible, does not achieve a sufficient effect due to the high rate of oxidation of the metals.

A technical solution that comes close to the invention is the German patent, Auslegeschrift 2425213, in which Auslegeschrift acidic rust conversion and rust protection agents in the form of aqueous dispersions, emulsions or solutions are described, which, in addition to the known rust converters based on aromatic carboxylic acids with at least one hydroxyl group, such as tannin and gallic acid, also contain a plastic binder. The plastic binders mentioned there either have no ionic groups, such as the polyvinyl acetate copolymers, styrene-butadiene rubbers or styrene-butadiene-acrylonitrile rubbers mentioned there, or they have hydroxy groups or anionic groups, such as carboxylate groups, as hydrophilic groups.

Examples of such plastic binders are phenolic resins, namely phenol-formaldehyde condensation products, alkyd resins, namely polyester resins obtained by condensation of polyhydric alcohols with polybasic acids, and epoxy resins, i.e. cross-linked polyether resins, which have free hydroxyl groups and unreacted epoxy groups at the chain ends.

The examples in this publication use water-soluble alkyd resins, for example with a fatty acid content of 45%, and non-polar resins based on styrene and butadiene.

preferably mixtures of these b*e«L*deR ^# , ve*r*v*an*det.

In the German patent, Auslegeschrift 2425213, in examples 1-7, a composition consisting of water-insoluble xylene or petroleum ether with the apolar resin and water with the water-soluble solution of isopropyl alcohol is described. In example 8, a composition consisting of water and methyl isobutyl ketone is described.

Although the polymer binder mentioned above contains hydrophilic groups, the polymer binders mentioned above have hydroxyl, anion or carboxyl groups, but do not have cation groups that ensure the chemical process of rust conversion.

Therefore, in the agent offered by the German patent, Auslegeschrift 2425213, not a single-phase solution is formed, but a solution consisting of a water phase and an organic phase. Such a solution consisting of a water phase and an organic phase and containing no cation group can only partially convert the rust, because the water-insoluble resins only partially impregnate the rust without forming any stable bonding compounds and consequently cannot produce a chemically resistant protective film.

Thus, the main disadvantage of the agent according to the German patent, Auslegeschrift 2425213, is the insufficient reaction with the rust substances, the residues of which remain under the polymer binder and the chemical destruction of metal continues.

Table 1 shows the data on the converting ability of the rust converter and the prototype.

Table 1

&igr;&igr;

According to the examplesiAverage thickness !Thickness of the converted

!the rust layer !rust layer

1 200 200

2 200 200

3 200 200

4 . 200 180

5 200 180 Rust conversion 200 80

after the prototype

The agent according to the German patent, Auslegeschrift 2425213, also contains a number of toxic solvents, e.g. Xy-

lol, butanol, isopropyl alcohol (see examples 1-7). Thus, the rust converter has insufficient conversion capacity, insufficient corrosion resistance of the coating, is environmentally harmful and has high toxicity.

The aim of the present invention is to create a rust converter with increased clothing conversion and corrosion ability, which is non-toxic and ecologically harmless thanks to the use of tannin extract, spruce needle/dwarf pine/pine bath salt, oxalic acid and water.

The recipe of the rust converter is shown in Table 2.

Table 2

description of 1
&igr; 15 Recipe, Weight &igr; 20, t 15 4 ! 22, 5 component I 10 1 ! 2 5, 12 ,&ugr; 3, 0 Tannin extract ,0 18 ,0 ,0 0 Spruce needle/ Lat ,0 8 ,0 sche/ pine 10 10. 7 2, Bath salts 3-% ,5 5 Oxalic acid ,0 5 ,0 3 Water ,0 ,0 other

The effect of the tannin extract and the spruce needle/dwarf pine/pine bath salt is that they convert the iron oxides into neutral, stable complexes, which then serve as an insoluble filler (instead of pigment) for the varnish and paint coating.

Oxalic acid (X^Cj^Q^ ) is readily soluble in water, creates a good acidic environment necessary for the active formation of ferritanates and accelerates the process of rust transformation by 3-4 times. The resulting oxalic acid salt forms an insoluble product in a complex with iron. Oxalic acid is a good solvent for iron corrosion products. When interacting with iron ions, oxalic acid forms not only oxalates, but also various complex compounds.

The results of the study showed (see Table 3) that oxalic acid gives good results when used as a component of rust converter. Firstly, 2.5-10% water solutions of oxalic acid dissolve just as well as lepidocronite, and also cronite, while at a concentration of oxalic acid of up to 10% a mass loss of up to 43-44% is ensured. Magnetite dissolves less, but quite adequately, and with an increase in the concentration of oxalic acid its solubility increases. It is noteworthy that after dissolving in oxalic acid, magnetite and wustite give a mass increase of +10^ to 18% (see Table 3) as a sintered precipitate covered with a yellow layer. These are complex compounds.

Table 3

Solubility of iron corrosion products in oxalic acid

(in %)

Material!Concentration- !Solubility of iron corrosion products !trationlLepido-
!the Lö-!cronit
!solution !and heating

i(in %) !tit &igr;&igr;

·

1 1

·

I I

:time of iron corrosion products

Hetite !Hetite !Magnetite!Magnetite !Magnetite !and !and mixture!mixture!mixture !Wustite !tite !of He- !mixture !

I tj_-j_ ■ T-I

!tit
&igr;

- ——&sfgr;^

!by Le-! !pido- ! !cronit !

Oxal 2, 50 27.03 30.61 12, 32 5.64 23.16 +13, 62 acid 5, 00 35.90 34.16 19, 88 11.78 29.56 + 18, 53 7, 50 37.16 39.24 22, 15 15.83 32.00 + 12, 15 10, 00 43.01 44.06 24 _? 80 20.60 34.16 +10, 98

This protects the metal surface under the effect of the corrosion converter from the subsequent influence of the corrosion-active components of the medium and from the "formation of corrosion

and thanks to the resulting protective film, passivation process takes place.

This rust converter based on tannin extract, spruce needle/dwarf pine/pine bath salt, oxalic acid and water (see Table 2) converts the corroded metal surface into an inert surface because it combines with the oxides present in the metal and forms an insoluble film. Iron tannates are converted into insoluble ferritanates under the influence of atmospheric oxygen. This film has molecular thickness and can be easily combined with most paints, varnishes and primers. It protects against premature deposits or blistering (on painted surfaces) and increases the covering power of the paint.

The samples were tested for the area of corrosion damage .

The paint coatings were applied 3 hours after the surface of the samples had been treated with the rust converter. The samples, 5 pieces of each variant, were painted with MP thick-layer primer 227 and MP thick-layer 229 in two layers.

The samples painted with MP Thick Film Primer 227 were dried for 4 hours at room temperature (20 C) and the samples painted with MP Thick Film 229 were dried for 5 hours at room temperature (20 C).

The painted and dried samples were immersed alternately in salt water (3% NaCl) and fresh water for 5 days, with a total cycle duration of 15 days. As a control, the samples were immersed in salt water only for 15 days. They were then dried and subjected to a visual inspection with the aim of detecting damage caused by fine costal rash, the presence of thickenings, fissures and detachment of the coating on the surface.

The results of the tests are shown in Table 4.

Table 4

!Area of corrosion damage

Test method ! on the 15th day after the example, %

! ! ! ! ! !Proto- ! 1 ! 2 ! 3 ! 4 ! 5 ! type With alternating

Immersion (every 5 days) in 3% solution of sodium

chlorides and ins

Freshwater Until Until Until Until Until Until With constant on 0.3 0.3 0.3 0.6 0.6 3.0 dip in 3% Solution of sodium 50 chlorides Until Until Until Until Until Until With constant on 0.1 0.1 0.1 0.3 0.3 2.5 dive into the sweet water

Table 5 shows the physical and mechanical characteristics of the rust converter according to the invention.

·_ —tT) —

Table 5 Designation of the parameters

! Standards

1. Appearance

2. Conditional viscosity, s, according to the viscometer VS-4 at temperature (20+0.5 ⁰ C)

3. Drying time of the film layer at temperature, C, hours

from 0 to 10 from 10 to 15 from 15 to 25 ~

4
5
6

g/cm

Density,
PH

Converting ability at medium rust thickness up to jUm , % not less than

7. Coating color

8. Adhesion of the paint coating on the converted surface

9. Lifespan of the Rostum converter

10.Compatibility with paint materials

ll.Toxicity
12.Freezing point, in C 13.Diluent 14.Consumption for ^ one layer g/m , when applying: -with the roller, with the brush

-with pneumatic spray systems

Liquid of brown color

11-14

3-5 3-4 2-3 1.07-1.12 4.0-4.5

100

Dark blue It passes the adhesion test using the grid incision method Permanent time (not limited) It is compatible with all types of paint and varnish materials Non-toxic

-5 water

100-200 120-140

Claims (2)

*· · 1 t 1 Protection Claims 1. Aqueous solution that converts rust and protects against further rusting, which has a pH value of 4.0-4.5 and contains a tannin extract and an acid as rust converter, characterized in that it contains the tannin extract as tannin extract, the oxalic acid as acid and additionally the spruce needle/dwarf pine/pine bath salt in the following ratio of the components in % by weight in order to increase the convertibility, the corrosion resistance of the coatings and to reduce toxicity: Tannery extract 15.0-20.0 Spruce needle/ mountain pine/ Pine Bath Salt 5.0-10.0 Oxalic acid 5.0-10.0 Water remaining 2. Composition according to claim 1, characterized in that it is packaged in a corrosion-resistant spray can and contains a propellant, preferably carbon dioxide, as a further component.