EP0038364A1 - Method of imparting rust resistance to steel materials - Google Patents

Abstract

Hot-rolled steel plates, acid washed, cold-rolled steel plates, cast iron, etc., are treated with an aqueous solution or emulsion having a pH between 7 and 10 and containing essentially a 1-hydroxybenzotriazole compound represented by the general formula: <IMAGE> (where X and Y each represent a hydrogen atom, a hydroxy group, an alkyl group, a carboxyl group, a nitro group or a sulfo group) and further containing one, two or more aliphatic dicarboxylic acids to give rust resistance to steel plates.

Description

The invention relates to the anticorrosion treatment of stored steel or of materials such as hot or cold rolled steel plates, cast iron, etc.

Generally, a surface treatment is applied to the surface of cold-rolled steel plates, and the like, to act against corrosion and preserve the beautiful appearance of the material.

However, as it takes a considerable period of time before the various types of steel plates and others, are transformed and used, they are coated with an anticorrosion oil, or chemically treated, or wrapped in anti-corrosion spray paper, or otherwise treated against corrosion. However, all of these known methods of combating corrosion have the following drawbacks.

The application of an anti-corrosion oil implies, not to mention the fact that the oil is sticky, the need for a degreasing step before using the steel plates, followed by the treatment of the used degreasing solution, which is the most annoying.

In addition, welding or other treatment of materials to which anticorrosive oil has been applied, presents problems such that the electrodes become dirty, considerable smoke is produced, and the working conditions become difficult.

Water-soluble anticorrosive agents, already known, for example sodium borate, aromatic carboxylic acids, imidazoles, amines and surfactants are used alone or in combination. Nevertheless, their anti-corrosion action is effective especially in water or in air, and it is rather weak when the steel plates touch in a humid atmosphere or in conditions where water adheres to them, or when 'they are stacked at high temperature and humidity, especially in a wet box according to JIS Z-0228. There are also anti-corrosion agents comprising aliphatic amines or long chain fatty acids. However, they also have drawbacks, namely that their drying is difficult and that a removal step is necessary when anti-corrosion oil is used.

The inventors have discovered that 1-hydroxybenzotriazole is an excellent anticorrosive agent for steel stored, according to Japanese Patent No. 27694/78. However, we also found a weak point of this product, namely that the steel discolours in some cases, when a drop of water falls on a treated steel plate, that another plate is placed on it, and that the cell is stored at high temperature and in an atmosphere of high humidity, although their anti-corrosion properties are excellent after being subjected to hot air drying.

The invention has eliminated these drawbacks and has made it possible to exert a very good anti-corrosion action without requiring a subsequent treatment.

Briefly, the invention is characterized in that an aqueous solution of 1-hydroxybenzotriazole and an aliphatic dicarboxylic acid is adjusted in a neutral range using an agent and that the adjusted solution is applied to the surface of metals to form an anti-corrosion coating.

The anti-corrosion action of the invention is not limited to a particular environment. This action is excellent not only in water and air, but also in an acid atmosphere, or at high temperature and humidity, when drops of water are present between the steel plates treated in contact with each other , or in other varied environments. when a hot rolling solution is dispersed or its vapor condenses in droplets on the high speed rolled steel plates.

dans laquelle X et Y représentent des atomes d'hydrogène et des groupes hydroxyl, alcoyl, carboxyl, nitro et sulfonique, et contenant simultanément un acide dicarboxylique aliphatique, par exemple, un ou plusieurs des acides subérique, azélaique et brassilique, est neutralisée avec de l'ammoniaque, de l'hydrazine, ou une alcanol amine comme la monoéthanolamine ou la triéthanol- amine pour obtenir une solution aqueuse ayant un pH situé entre 7 et 10, et que l'on applique sur de l'acier stocké. La solution aqueuse peut être utilisée après que l'on y ait ajouté un composé à haut poids moléculaire soluble dans l'eau, ou un tensioactif. Ensuite, l'objectif peut être atteint en ajoutant la solution aqueuse mixte à une émulsion comme un mélange aqueux d'huile de coupe, d'abrasion ou de laminage, ce qui permet de former un revêtement anticorrosion. Dans ce cas, la concentration du 1-hydroxybenzotriazole de la formule générale ci-dessus et de ses dérivés contenus dans la solution résultante est de l'ordre de 0,01-10 % (% en poids, dans ce qui suit aussi) et l'acide dicarboxylique aliphatique ajouté peut être utilisé dans un ordre de grandeur de 0,01-5 %. De préférence, le composant principal, le 1-hydroxybenzotriazole et l'additif, l'acide dicarboxylique aliphatique, sont utilisés à O,1-2 % du point de vue de l'effet anticorrosion et de l'aspect économique. En outre, une proportion de 0,001-0,5 % de tensioactif est ajoutée et éventuellement 0,01-2 % d'un composé de poids moléculaire élevé peuvent être ajoutées, ce qui est préférable pour l'effet anti-corrosion et l'uniformité du revêtement qui va contribuer à renforcer les propriétés anti-corrosion.According to the invention, a mixed aqueous solution, essentially consisting of a 1-hydroxybenzotriazole compound, represented by the general formula:

in which X and Y represent hydrogen atoms and hydroxyl, alkyl, carboxyl, nitro and sulfonic groups, and simultaneously containing an aliphatic dicarboxylic acid, for example, one or more of the suberic, azelaic and brassilic acids, is neutralized with ammonia, hydrazine, or an alkanol amine such as monoethanolamine or triethanolamine to obtain an aqueous solution having a pH between 7 and 10, and which is applied to stored steel. The aqueous solution can be used after adding a water soluble high molecular weight compound, or a surfactant. Then, the objective can be achieved by adding the mixed aqueous solution to an emulsion as an aqueous mixture of cutting, abrasion or rolling oil, which makes it possible to form an anticorrosion coating. In this case, the concentration of 1-hydroxybenzotriazole of the general formula above and of its derivatives contained in the resulting solution is of the order of 0.01-10% (% by weight, in the following also) and the added aliphatic dicarboxylic acid can be used in an order of magnitude of 0.01-5%. Preferably, the main component, 1-hydroxybenzotriazole and the additive, aliphatic dicarboxylic acid, are used at 0.2-2% from the point of view of the anticorrosion effect and the economic aspect. In addition, a proportion of 0.001-0.5% of surfactant is added and optionally 0.01-2% of a high molecular weight compound can be added, which is preferable for the anti-corrosion effect and the uniformity of the coating which will help to reinforce the anti-corrosion properties.

The invention is also characterized in that painting or direct deposition is possible on the surface of the stored steel treated according to the invention, with the same result as if they were applied to untreated surfaces.

The invention will be better understood using the examples described below:

Example 1:

An aqueous solution containing 0.5% of 1-hydroxybenzotriazole and 0.3% of azelaic acid is adjusted to a pH of 8, by adding monoethanolamine as a neutralizing agent, to give a treatment solution. A steel material is subjected to a traditional rolling, and water is applied to a part of this material which is then wound up.

Example 2:

An aqueous solution, prepared by adding 0.2% of azelaic acid and then 0.03% of a nonionic surfactant (a polyoxyethylene alkyl ether) at 0.4% of 1-hydroxybenzotriazole, is adjusted to pH 8 by addition of monoethanolamine, to obtain a treatment solution. This solution is sprayed continuously on a steel plate cold rolled, and surface cleaned. Immediately after, the plate is treated with rubber cylinders and dried.

Example 3:

An aqueous solution prepared by adding 12.3% sebacic acid and 0.1% acrylic resin, a high molecular weight material soluble in water, 0.4% of 1-hydroxybenzotriazole, is adjusted to pH 8 by addition of monoethanolamine to obtain a treatment solution. This solution is continuously sprayed onto a cold-rolled steel plate, cleaned on the surface, and this plate is immediately treated with rubber cylinders and dried.

Example 4:

An aqueous solution prepared by adding 0.2% of sebacic acid and 0.03% of a nonionic surfactant (a polyoxyethylene alkyl ether) at 0.5% of 1-hydroxybenzotriazole, is adjusted to pH 9 by addition monoethanolamine, to obtain a treatment solution. This is sprayed continuously on a cold rolled steel plate, cleaned on the surface. Immediately after, the plate is treated with rubber cylinders and dried.

The results of the anticorrosion tests with the steel plates treated according to the above methods in accordance with the invention, and of the reference tests, are grouped in Table 1, and the results of direct painting, in Table 2.

The test pieces are the same as in the primary adhesion test.

Ratings: (10) excellent - O (failure).

Thus, in accordance with the invention, not only the targeted anticorrosion action can be applied under various environmental conditions, but it is also possible to avoid the elimination of the anticorrosion agent before the next step, and painting or the like. necessary treatment can be carried out directly, which improves working conditions. In addition, the problem of toxicity which has appeared recently in the case of the traditional treatment with sodium nitrite, is extremely slight in the case of the invention, and in welding or other operations, there is no pollution by smoke, or dirt on the electrodes hindering work. Thus, the method according to the invention has many advantages over traditional methods of treatment.

Claims (1)

Process for the anti-corrosion treatment of stored steel, characterized by the treatment of the stored steel with an aqueous solution or an emulsion, essentially consisting of a 1-hydroxybenzotriazole compound represented by the general formula:

in which X and Y represent hydrogen atoms and hydroxyl, alkyl, carboxyl, nitro and sulfonic groups, and also containing one or more aliphatic dicarboxylic acids, and having a pH of the order of 7 to 10.