DD219801A1 - TEMPORARY PROTECTION FOR HEAVY METALS - Google Patents

Abstract

The invention relates to a temporary Schutzueberzug for heavy metals, preferably for galvanized components. This is to avoid that rust or white rust can form, otherwise mechanically or chemically treated surfaces of heavy metals are otherwise often covered. According to the invention, a reaction with an inhibitor solution is brought about on the pretreated surfaces of the components in a treatment bath. The solution preferably contains nitrites and silicates, such as NaNO 2 and Na silicate. The method is preferably used for galvanized components; However, the treatment can also be carried out for bare steel after a chemical and / or mechanical process according to the same procedure.

Description

Title of the invention

Temporary protective coating for heavy metals ·. ·· _

Field of application of the invention

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The invention relates to a temporary protective coating for heavy metals, preferably for hot-dip galvanized components.

Characteristic of the known technical solutions

After treatment of metal objects, such as components which have undergone a galvanizing process, or those which have received chemical or mechanical de-rusting as bare steel, they tend, through a series of environmental influences, to form on the surface γοη Zinc (OH) ₂ , ZnSO, ZnCl ₂ ) / and on bare parts Plugrost and in the extreme leaf rust forms. In all cases, the mentioned atmospheric influences, such. 3. Dew, snow, pollutant emissions of the air and the like. Technically and economically not exclude any time and sometimes lead to permanent damage to the surfaces. While the bare steel must be fed as soon as possible a further surface treatment,

In most cases, white rust formation on galvanized surfaces can only be countered by proper transport and storage as well as by post-treatment.

To avoid ,, this white rust formation processes are already known, which provides immediately after the galvanizing process, the application of a protective coating of oils, fats or waxes. The formation of CO ₂ in the atmosphere gradually eliminates the need for a passive layer which is gradually formed. The premature removal of wax, oil, etc. is particularly important in the case of a subsequent coating of paint ( Luplex systems) is required, ie, zinc plus paint, requires time-consuming and costly removal with solvents. However, if the protective layer remains on the components, it poses an extraordinarily high risk to the assembly personnel on the building sites The disadvantage is that this layer promotes the adhesion of dirt, such as sand in dry-warm climates.

To avoid the formation of white rust, the chromating or phosphating is customary after application of the Znnküberzüge. The aftertreatment baths with chromic acid or ..

Phosphate acid are highly toxic. They require constant monitoring during the treatment process. visibly cessation of their concentration as well as a technically and costly high expenditure for the neutralization and detoxification of derived process solutions.

In addition, technical systems are required for the chromating and phosphatisation process, which>^; are uneconomical for large galvanizing plants.

There has also been found a method and apparatus for preventing the formation of white rust on galvanized surfaces, but which is preferred for

In this process, freshly galvanized components within a closed reaction space are exposed to a diffuse stream of gases, preferably industrial effluents consisting of COpHpO, at elevated temperature over a longer residence time In the case of large parts, the expense of high-temperature gas increases so much that economical use is no longer possible.

Object of the invention

The object of the invention, while avoiding rust, white rust and the like, is to make no special demands on the storage technology of the treated metal parts, to avoid a cost for hard-to-remove protective coatings which is customary in various processes and to use no toxic substances for the temporary treatment. Furthermore, the method should be applicable with relatively low material and operating costs for the medium to be used and a high construction cost for the application of the insurance, driving3 be excluded ·

Explanation of the essence of the invention

Apart from the fact that especially small parts can be optimally protected with known aftertreatment methods, the novel method should preferably be applicable to large and structurally complicated components and assemblies at high throughputs ·

The invention therefore has the task of protecting the components and groups described to the extent that environmental influences can not interfere with their surface. The temporary protective cover to be attached

may not be detrimental to technical or industrial safety for subsequent treatment; the spent process solution should have no environmentally harmful effects. It should be able to be maintained by .A purification in the process process in the circulation and therefore eliminates a detoxification or neutralization of derived spent liquid. The construction of aftertreatment baths must not be subject to any major technical effort. "The application of a one-stage aftertreatment, preferably in existing sections of the technical systems, should be possible. .

According to the invention, this object is achieved by immersing, on a mechanical basis, heavy metal components which have been purified and / or treated by chemical and physical electrolytic means, including further purification and preservation processes, in a treatment bath for reaction with an inhibitor solution which preferably contains nitrites and silicates becomes. The inhibitor solution contains at least NaNO ₂ and Na silicate or nitrites and silicates on another basis. The inhibitor solution can be enhanced by disilicate, such as NapSiO-. The concentrate for the inhibitor solution has a NaNO.sub.p content of about 5-45%, preferably about 20%, and Na silicate of 0, 5 - 12%, preferably around 2.0%.

The concentrate for the inhibitor solution can by 'addition. of some per mille of disilicate yet to be exacerbated.

Analogous to the process steps that are used after a galvanizing process, the same treatment can also be carried out for bare steel after a chemical and / or mechanical process. ,,

Embodiment,>

, The invention will be explained in more detail by one embodiment of its application after the application of zinc protective coatings on steel.

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, The. Steel structural parts which are fed to the galvanizing process undergo various pre-treatment baths in a known manner before they are immersed in the liquid zinc bath. Immediately after the galvanizing process - so if the components still have a temperature of about 300 ⁰ C - they are lowered into the appropriate immersion bath · This dip can both the galvanizing process downstream rinsing or sufficiently existing rinsing stages before the galvanizing in a designated tub »The dipping the appropriate process solution is added, with a residence time in the relation between bath temperature and heat of the introduced material of fractions of a minute is sufficient to react the chemically active zinc with the inhibitors of the process solution. After pulling out the components from the process solution, they can be immediately brought to the appropriate warehouse, as a result of the heat of the steel components drying of the adhering process solution. The temporary protective coating ensures that the gradual entering passivation process can not be interrupted by Schademission and Weißrostbefall.

The immersion bath should preferably have a temperature below the boiling point of water. At the same time it is achieved that the quenching and chemical treatment of the galvanized components a blasting u »a. of zinc ash, hard zinc and Plufmittelresten effected in an advantageous manner. The impurities remaining in the dipping bath are to be removed in a cycle, which is to be determined depending on the respective technology, by decanting, filtering 0. Ä.

The concentration of the active inhibitors is through the cyclic addition of inhibitor concentrate in the process solution depending on the use cycle by

known analytical methods controlled and regulated »

In galvanizing plants with high throughput rate and quantity, the introduced energy of the freshly galvanized parts can lead to strong heating of the inhibitor solution. Pur such 'cases, a cooling system, which z. B. can be used as a circulation system for energy recovery, provided.

Claims (6)

Claims. 1. A process for forming a protective coating on 'heavy metals, characterized in that cleaned and / or post-treated steel parts in a treatment bath by reaction with an inhibitor solution, which preferably contains nitrites and silicates, is immersed. '. -,. 2. The method according to item 1, characterized in that the inhibitor solution at least NaHO ₂ and Na silicate contains. , 3 method according to item 1 and 2, characterized that the inhibitor solution by disilicate, such as Na ₂ SiO .., / is enhanced. 4. The method according to item 1 and 2, characterized in that the concentrate for the Inhibitor Lösuhg has a content of NaUTO ₂ of about 5-45 % and Na silicate of 0.5 to 12 % . 5. The method according to item 1 to 4 », characterized in that the concentrate for the inhibitor solution is enhanced by the addition of per Mille portions of disilicate. 6. The method according to item 1 to 5, characterized in that bare steel is treated by chemical and / or mechanical treatment analogous to these process steps. ^: