CS242440B1 - Silicic acid based coating agent for rust protection of steel and cast iron surfaces - Google Patents

Abstract

The problem of the composition of a composition which would serve to protect steel and cast iron products from rusting under the influence of the atmosphere and at the same time increase the adhesion of organic coatings subsequently applied to the surface of these products is solved. The composition according to the invention contains as the main component a silicic acid salt, further in defined proportions orthophosphoric acid, alcohols and/or ethers with a boiling point above 78 °C and a component forming insoluble compounds with Fe2+ and Fe>+ ions.

Description

(54) Silicic acid coating agent for the protection of steel and cast iron surfaces against rust formation

It solves the problem of the composition of a composition which would protect steel and cast iron products from rust formation by the atmosphere and at the same time increase the adhesion of organic coatings applied subsequently to the surface of these products. The composition according to the invention comprises as a main component a silicic acid salt, furthermore in defined proportions orthophosphoric acid, alcohols and / or ethers with a boiling point above 78 ° C and a component which forms insoluble compounds with Fe 2+ and Fe 2+ ions.

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FIELD OF THE INVENTION The present invention relates to a silica-based coating composition for protecting steel and cast iron surfaces against atmospheric rust.

Ensuring the corrosion resistance of mechanically or chemically machined steel and cast iron surfaces. Due to the atmosphere is an important technical challenge in many manufacturing industries. Maintaining a metal-clean surface, obtained by machining, blasting or grinding, during subsequent manufacturing operations so that the final product coating does not need to remove all rust from the product is difficult to achieve. In particular, temporary protection agents based on petroleum products or waxes, contact or evaporation corrosion inhibitors, phosphating agents and shop primers are known to provide protection of the surface of steel and cast iron against atmospheric rust. Their use depends on the aggressiveness of the atmospheric conditions during the period of further processing, storage and transport of the products, the efficiency requirement and the need to either remove the protective coating before further manufacturing operations or use it as a component of the final protective system. From these aspects, the means used hitherto have some disadvantages. While preservative agents are highly effective in terms of protective function, their use requires thorough cleaning of the canned parts with solvents or hot water degreasing agents before further manufacturing operations to ensure the handling of the parts, not to complicate welding and to ensure the necessary surface cleanliness before application.

- 2,242,440 coatings. This deconservation is a technically and time-consuming operation that brings problems with the production of fire safety, work hygiene and waste disposal into production.

The use of inhibitors is limited to smaller parts which, during welding and transport, can be stored in sealed packages, the reversibility of which is an important economic condition for the use of this method, in particular for in-process protection. The inhibitor-protected parts lose their resistance after being removed from the protective packaging, but on the other hand, this method does not affect the subsequent technological operations.

Conversion coatings are made either hot or cold The typical representative of a hot-finished conversion coat is phosphating, which takes place on special production dip or spray lines. The process is multi-stage and its negative features are considerable - space and investment demands, high energy and water consumption and the need to dispose of waste products. The protective effect of phosphate coatings is good, especially when stored in confined spaces. Another alternative is modern cold phosphating processes, which form very thin coatings with an organic binder component. Compared to conventional phosphate coatings, they have lower protective efficacy, but their use is considerably easier to manufacture. In some cases, phosphate coatings make subsequent manufacturing operations, such as welding, more difficult

Workshop primers based on organic binder base cause technological and hygienic welding difficulties, especially if they contain pigments that release toxic fumes at welding temperatures. Inorganic workshop bases, for example the so-called zinc silicate, are demanding in terms of raw material base.

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The known means for protecting steel and cast iron surfaces against atmospheric corrosion improves the silica-based composition for coating the steel and cast iron surfaces against atmospheric corrosion according to the invention. Its essence is that it contains, in 1 liter, from 50 to 300 g of silica in the form of a silica sol, from 6 to 20 g of orthophosphoric acid, from 5 to 100 g of an insoluble compound with Fe 'and Fe ions selected from groups of substances including natural and

O-modified tannins, Fe (CN) g7 ions Fe (CN) g7 multifunctional phenols, for example dihydroxybenzene, and hydroxy derivatives of nitrogenous heterocyclic compounds, for example 8-hydroxyquinoline, from 30 to 100 g of alcohols and / or ethers boiling above 78 ° C , for example n-butyl alcohol, and water in an amount necessary to make up the volume to 1 liter.

The composition according to the invention comprises ingredients which are available and do not create the need for special hygiene or water management measures, either during manufacture or in use.

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The effect of the composition according to the invention consists in its chemical reaction with a metal surface, which forms a protective layer on the surface, in which at the same time a silica gel is formed by coagulation of the sol. The agent, when it comes into contact with the steel and cast iron surfaces under controlled working conditions, causes simultaneous formation of insoluble reaction fumes and silicic acid xerogel, or its complex with phosphoric acid, which binds the layer and creates suitable conditions for good adhesion of subsequent coatings. , such as organic.

The invention and its effects are further explained in more detail by way of examples of a specific embodiment thereof.

Example 1

A composition was formulated to form non-aggressive black-violet color coatings by pneumatic spraying

- 4,242,440 in the composition: in 60 l of a silica sol containing 30 wt.

% SiOg was dissolved 5 kg of natural tannin. The mixture was acidified with vigorous stirring with 1.2 L of H = 1.71. After addition of 6 L of n-butyl alcohol, the mixture was made up to about 33 L of water to 100 L with stirring. The resulting pH of the mixture was 2.0. The mixture did not appear to coagulate at ambient temperature for at least 14 days. The obtained mixture had a suitable consistency for pneumatic spraying.

When thinner coatings were needed, the mixture was diluted to twice its volume with water without reducing the pot life.

Example 2

A composition containing 50 l of silicic acid sol, 1.0 l of orthophosphoric acid oh = 1.71, 2 kg of pyrogallol, 4 kg has proven to be a non-rinsing anti-corrosion treatment of small steel parts with a dark brown, non-washable coating made by dipping parts on hinges or baskets. mixtures of hydroquinol, resorcinol and pyrocatechol (dihydroxybenzenes), 10 l of a mixture of ethylene glycol mopoethylether with isopropyl alcohol and glycerin in volume ratios of 1: 3: 1 and made up to 100 l with water at pH 1. for 1 month at -5 ° C to 30 ° C.

Example 3

The preparation for making thin, brown-colored layers by immersion has the following composition: 30 l of silica sol containing 30% SiOg, 2 kg of 8-hydroxyquinoline, 0.5 l of orthophosphoric acid oh = 1.71, 5 l of n-butyl alcohol diluted with water The pH of the solution was 2.1 and the solution showed no tendency to increase viscosity and deposit formation for 14 days.

Example 4

A coating composition similar to that of Examples 1 and 2 has proven useful in the formation of dark blue coatings, but instead of tannin or di- and trihydroxybenzene, 8 kg of hexacylate ferrate or hexacylate ferrite are used per 100 l of the formulation.

242 440 sodium or potassium. In this case, the processability of the mixture is reduced to 7 to 10 days and the protective performance of the coatings is less than that of the formulations of Examples 1 to 3.

The invention can be used in mechanical engineering.

Claims (2)

BACKGROUND OF THE INVENTION Silicic acid-based coating for the protection of steel and cast iron surfaces against atmospheric rust, characterized in that it contains from 1 to 50 g of silica in the form of a silica sol, from 6 to 20 g orthophosphoric acid, from 5 to 100 g 2+ 3+ components forming insoluble compounds with Fe and Fe ions selected from the group consisting of natural and modified tannins, Fe (CN) g 7 Fe (CN) g 7 multifunctional phenols, for example dihydroxybenzene, and hydroxy derivatives of nitrogenous heterocyclic compounds, for example 8- hydroxyquinoline, from 30 to 100 g of alcohols and / or ethers having a boiling point above 78 ° C, for example n-butyl alcohol, and water in an amount necessary to make up the volume to 1 liter.