FR3048703A1 - METHOD AND SYSTEM FOR ANTI-CORROSIVE TREATMENT AND CORRESPONDING COMPUTER PROGRAM - Google Patents

Abstract

The invention relates to a method of anticorrosion treatment. Such a method comprises a step of anticorrosion treatment of a workpiece, said processing step (T02) of dipping said workpiece, for a period of between 10 and 20 minutes, in a treatment bath comprising per liter of solution, 560 and 660 g of alkaline hydroxides, between 75 and 95 g of nitrates and / or of alkaline nitrites, between 75 and 95 g of borax and 40 g of at least one surfactant, this bath being heated to a temperature between 130 and 160 ° C.

Description

Method and system for anticorrosion treatment and corresponding computer program 1. Domain

The present technique relates to an anticorrosive treatment, to be applied to metal parts. More particularly, the present technique relates to an anticorrosion treatment of ferrous metal parts.

Corrosion means the alteration of a material by chemical reaction with an oxidant. The best-known examples are the chemical alterations of metals in air or in water, such as iron and steel rust or the formation of verdigris on copper and its alloys (bronze, brass ).

During corrosion, the metals are attacked and become hydrated ions, oxides or hydroxides. This transformation, often progressive, leads to a loss of the intrinsic qualities of the metal, and therefore a significant financial loss.

In order to overcome these problems, specialists have proposed various methods of a nature to improve the corrosion resistance of metal parts. There are mainly processes consisting of coating the piece with a continuous layer, itself resistant to corrosion (tinning, galvanizing, chromium plating, phosphating, etc.) and processes consisting in forming on the surface of the piece a layer surface oxidized continuous and sealed, among which may be mentioned the methods of immersing the parts in baths of molten oxidizing salts operating at very high temperatures.

In spite of their qualities, these processes present, to varying degrees, problems which it is necessary to solve. In fact, the existing processes have, for example, cost prices that are too high, efficiency or insufficient strength (risk of flaking). They also have reproducibility problems.

Moreover, such processes also have environmental problems: they produce more or less significant amounts of sludge or waste toxic or harmful to the environment (chromium, copper, zinc, nickel, ..). A number of these processes have been banned because of the serious risks they pose to the environment.

It is therefore necessary to provide a method that does not have these disadvantages of the prior art. 3. Summary

The described technique does not have these disadvantages of the prior art. More particularly, the described technique relates to a method and an anticorrosion treatment system involving a reduced amount of chemical compound and generating an equally reduced amount of pollutant.

Thus, the described technique relates to an anticorrosion treatment process which comprises a step of anticorrosion treatment of a workpiece, said processing step of plunging said workpiece, for a period of between 10 and 20 minutes, in a bath of treatment comprising, per liter of solution, 560 and 660 g of alkaline hydroxides, between 75 and 95 g of nitrates and / or of alkaline nitrites, between 75 and 95 g of borax and 40 g of at least one surfactant, bath being heated to a temperature between 130 and 160 ° C.

Thus, unlike prior art, the anticorrosive effect is maximized while limiting the consumption of chemical agents that may be harmful to the environment.

According to a particular embodiment, the treatment method further comprises, prior to said anticorrosion treatment step, a step of anticorrosion pretreatment of said workpiece, said pretreatment step of plunging said workpiece for a period of time between 10 and 20 minutes, in a treatment bath comprising, per liter of solution, 630 and 770 g of alkaline hydroxides, between 60 and 80 g of nitrates and / or of alkaline nitrites, between 60 and 80 g of borax, this bath being carried at a temperature between 130 and 160 ° C.

This pretreatment makes it possible to prepare the part for the treatment by making sure to partially modify the surface of the metal part, so that it can undergo the subsequent treatment in depth.

According to a particular embodiment, the method further comprises a preliminary step of preparing said part, said preparation step comprising at least one degreasing step and at least one etching step.

This preparation phase can be carried out before the pretreatment if it exists or directly before the treatment in the absence of pretreatment (when pretreatment is optional)

According to a particular characteristic, said preliminary step of preparing said part comprises: a step of pre-degreasing the workpiece, comprising the use of an alkaline pre-degreasing solution, at a temperature of between 65.degree. 75 ° C, for a period of between 10 and 20 minutes; a step of degreasing the workpiece, comprising the implementation of an alkaline degreasing solution, at a temperature between 65 ° C and 75 ° C, for a period of between 10 and 20 minutes; a rinsing step, with water, at a temperature between 65 and 75 ° C, for a period of between 5 and 10 minutes; at least one rinsing step at room temperature for 2 to 5 minutes; a pickling step in a solution of hydrochloric acid diluted between 30 and 35% for a period of between 10 and 20 minutes; at least one rinsing step, at a room temperature for 2 to 5 minutes.

According to another aspect, the present technique also relates to a corrosion treatment system characterized in that it comprises an anticorrosion treatment tank of at least one workpiece, said treatment vessel comprising a treatment bath comprising per liter of solution, 560 and 660 g of alkali hydroxides, between 75 and 95 g of nitrates and / or of alkaline nitrites, between 75 and 95 g of borax and 40 g of at least one surfactant, this bath being brought to a temperature between 130 and 160 ° C, bath in which the workpiece takes place for a period of between 10 and 20 minutes. 1) According to a particular embodiment, such an anticorrosion treatment system also comprises an anticorrosion pretreatment tank of said workpiece, said treatment vessel comprising a pretreatment bath comprising per liter of solution, 630 and 770 g of hydroxides alkaline, between 60 and 80 g of nitrates and / or of alkaline nitrites, between 60 and 80 g of borax, this bath being brought to a temperature between 130 and 160 ° C, bath in which the workpiece takes place during a duration of between 10 and 20 minutes.

According to a preferred implementation, the various steps of the methods according to the proposed technique are implemented by one or more software or computer programs, comprising software instructions intended to be executed by a data processor of a relay module according to the technique. proposed and being designed to control the execution of the different process steps.

Accordingly, the proposed technique is also directed to a program that can be executed by a computer or a data processor, which program includes instructions for controlling the execution of the steps of the methods as described.

This program can use any programming language, and be in the form of source code, object code, or intermediate code between source code and object code, such as in a partially compiled form, or in any other form desirable shape.

The proposed technique is also aimed at a data carrier readable by a data processor, and including instructions of a program as mentioned above.

The information carrier may be any entity or device capable of storing the program. For example, the medium may comprise storage means, such as a RAM, a flash memory, a ROM, for example a CD ROM or a microelectronic circuit ROM, or a magnetic recording means, for example a diskette. (floppy dise) or a hard drive. On the other hand, the information medium may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means. The program according to the proposed technique can be downloaded in particular on an Internet type network.

Alternatively, the information carrier may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the method in question.

According to one embodiment, the proposed technique is implemented by means of software and / or hardware components. In this context, the term "module" may correspond in this document as well to a software component, a hardware component or a set of hardware and software components.

A software component corresponds to one or more computer programs, one or more subroutines of a program, or more generally to any element of a program or software capable of implementing a function or a program. set of functions, as described below for the module concerned. Such a software component is executed by a data processor of a physical entity (terminal, server, gateway, router, etc.) and is capable of accessing the hardware resources of this physical entity (memories, recording media, bus communication cards, input / output electronic cards, user interfaces, etc.).

In the same way, a hardware component corresponds to any element of a hardware set (or hardware) able to implement a function or a set of functions, as described below for the module concerned. It may be a hardware component that is programmable or has an integrated processor for executing software, for example a processor, a central unit, a supercomputer, an integrated circuit, a smart card, a memory card, a card electronics for running firmware, etc.

Each component of the previously described system naturally implements its own software modules. The various embodiments mentioned above are combinable with each other for the implementation of the proposed technique. Other features and advantages will appear more clearly on reading the following description and examining the figures that accompany it. 4. Figures Other features and advantages of the proposed technique will appear more clearly on reading the following description of a preferred embodiment, given as a simple illustrative and non-limiting example, and the appended drawings, among which: Figure 1 illustrates the different steps of the method of the present technique; FIG. 2 illustrates the different stages of filling the tanks used during the treatment; Figure 3 simply describes the structure of an electronic process management device of the present. 5. Description 5.1. Description of an embodiment

The present technique overcomes at least some of the disadvantages of the prior art by disclosing a method of anticorrosion treatment of multi-bath metal parts. One embodiment of the technique is described with reference to FIG. 1. There is described a method, which comprises, principally, a pretreatment step (PO1), lasting between 10 and 20 minutes, in a bath whose temperature is between 130 ° C and 160 ° C. The composition of this bath for pretreatment is explained below. The process also comprises a treatment step (T0 2), lasting between 10 and 20 minutes, in a bath whose temperature is between 130 ° C. and 160 ° C. It is noted that pretreatment is not necessary for the implementation of the present technique. However, the inventors have found that this pretreatment makes it possible to obtain better results under standard operating conditions. Moreover, the use of a pretreatment stage makes it possible, in a clever way, to use less quantity of chemical compounds and to significantly reduce the waste resulting from the treatment.

The composition of the pretreatment bath is as follows:

Sodium hydroxide 700g / liter;

Sodium nitrate 70g / liter;

Borax (sodium tetraborate) 70g / liter;

The values above are the values that show the optimal efficiency, from the point of view of pretreatment. These values support a certain tolerance: the concentration tolerance range: +/- 10% aii ^ if the temperature range (Temperature: +/- 10%). A temperature of 145 ° C offers very satisfactory results. The pre-treatment time (i.e. the soaking time) is on average 15 minutes (average time for workpieces grade XC, for example).

The composition of the treatment bath is as follows:

Sodium hydroxide 500g / liter;

Sodium nitrate 85g / liter;

Borax (sodium tetraborate) 85g / liter; trisodium phosphate 40g / liter;

Sodium carbonate 40g / liter.

As for pretreatment. The values above are the values which show the optimal efficiency, from the point of view of the anti-corrosion treatment. These values support a certain tolerance: the concentration tolerance range: +/- 10% as well as the temperature range (Temperature: +/- 10%). A temperature of 145 ° C offers very satisfactory results. The pre-treatment time (i.e. the soaking time) is on average 15 minutes (average time for machined parts grade XC).

Depending on the operational conditions, the preprocessing step may be preceded by a preparation step (OOP). This preparation step comprises: a pre-degreasing step (POOl) of the workpiece, comprising the use of an alkaline pre-degreasing solution, at a temperature of between 65 ° C. and 75 ° C., during a period of duration of between 10 and 20 minutes (for example 15 minutes); a step of degreasing (P002) the workpiece, comprising the implementation of an alkaline degreasing solution, at a temperature between 65 ° C and 75 ° C, for a period of between 10 and 20 minutes (for example 15 minutes) ; a rinsing step (P003), with water, at a temperature between 65 and 75 ° C, for a period of between 3 and 10 minutes (for example 3 minutes); at least one rinsing step, at a room temperature for 2 to 5 minutes (for example 3 minutes); in one embodiment three rinsing steps at room temperature are performed; this rinsing is performed after the degreasing so as not to pollute the following preparation operations; a pickling step, in a solution of hydrochloric acid diluted between 30 and 35%, for a period of between 10 and 20 minutes (for example 15 minutes), depending on the workpiece and the size thereof ; at least one rinsing step, at a room temperature for 2 to 5 minutes (for example 3 minutes); in one embodiment three rinsing steps at room temperature are performed; this rinsing is performed after the degreasing so as not to pollute the following preparation operations; This preparation step makes it possible to have a cleaned part of its impurities, including those which can remain despite a conventional cleaning. It can also be noted that this preparation step is similar to that implemented during a galvanizing process, unlike the hot rinsing step which occurs after degreasing: this step makes it possible to maximize the effects. degreasing.

Depending on the operating conditions, the treatment step may be followed by a finishing step (T03). This preparation step comprises: at least one rinsing step (T031), at an ambient temperature for 2 to 5 minutes (for example 3 minutes); in one embodiment three rinsing steps at room temperature are performed; this rinsing step is said to be "agitated" in that it uses compressed air in the rinsing bath; a rinsing step (T032), with water, at a temperature between 65 and 75 ° C, for a period of between 3 and 10 minutes (for example 3 minutes); a dewatering step (T033); a drying step (T034).

This multi-bath technique has many advantages among which that of being able to process in parallel, without loss of time, several metal parts to perform anticorrosive treatment.

Indeed, the times required for degreasing, rinsing, pretreatment and treatment are similar. In a particular embodiment, the times required for these different steps are adjusted to be substantially equal. Thus, the degreasing step is adjusted to be of equal duration to the rinsing steps, the pre-treatment stage and the treatment stage. The rinsing and drying steps subsequent to the treatment are shorter than the duration of the treatment itself and therefore do not pose particular constraints in terms of parallelization. To illustrate the possible parallelization offered by the method, Figure 1 includes indicative times (15 minutes) for the previously presented steps. It can be seen that the intermediate rinsing steps, which serve to clean the room after a given treatment can advantageously be adapted, in time, to ensure optimal parallelization of the process. Thus, for example, the flushing steps P003 and P004 can be adjusted so that their duration is equal to 15 minutes. Similarly, the flushing step P006 can also be extended so that it lasts 15 minutes.

Moreover, in order to limit toxic discharges and to save as much raw material as possible, the process is carried out in a closed circuit: an upgrade of the various baths is carried out by complement treatment stage in "reverse cascade" At least polluted to the most polluted. Such a technique makes it possible to obtain less rinsing effluent to be treated.

Thus, for example, such an addition is carried out in the following manner: Hot degreaser <-1® 'cold rinse <-2® ™ cold rinse <-3®' ^ ® cold rinse-supplement in clean water. In a more extensive manner, at regular intervals (for example depending on the number of parts processed and / or their volumes), described in connection with FIG. 2: at least a part of the pre-degreasing bath (bath of the stage POO1) is extracted from the tank (Bpd) used for this bath and constitutes a waste (D); at least a portion of the degreasing bath (bath of step P002) is extracted from the tank (Bpd) used for this bath and poured into the tank of the pre-degreasing bath (Bpd) to perform the complement; a sufficient amount of pre-degreasing agent (PA) is added to the tank (Bd) of the degreasing bath in order to respect an adequate concentration the complement of the degreasing bath is carried out with water coming from the tank (Brc) of the rinsing bath hot (bath of step P003); a sufficient quantity of degreasing agent (A) is added to the tank (Bd) of the degreasing bath in order to respect an adequate concentration, the complement of the hot rinsing bath is carried out with water coming from the tank (Brfi) the first cold rinse bath; the addition of the first hot rinse bath is carried out with water from the tank (Brf2) of the second cold rinse bath; the addition of the second hot rinse bath is performed with water from the tank (Brfs) of the third cold rinse bath; clean water (E) is added to the tank (Brfb) of the third cold rinse bath.

The same method can also be applied for pickling and during processing (and anti-corrosion pretreatment). At the environmental level, the proposed operating mode makes it possible to greatly limit atmospheric emissions and makes it possible to limit the quantities of liquid effluents or solid wastes emitted.

The method described above is suitable for the treatment of ferrous metal parts (iron, cast iron and steel); its implementation can also be adapted to other metals or alloys, such as, for example, zamak or aluminum. In general, pretreatment and anticorrosive treatment involves the use of hydroxide as well as nitrate and / or sodium nitrite. The surfactant (s) contained in the treatment bath may, for their part, be anionic and / or cationic, or even nonionic depending on each particular case;

The treatment bath acts on the metal part in several phases:

In the first place, the hydroxide and, to a lesser extent, the nitrate and / or sodium nitrite alters the metal surface to a thickness of about 15 to 20 μm, (molecular pore opening) as a function of the hardness of the metal, so as to create a protective layer deep perfectly adherent surface. Secondly, borax makes it possible to maintain this altered surface in a stable state in order to allow the surfactants to penetrate and to seal the altered surface.

Third, the nitrate (or nitrite) acts as a healing agent to close the previously closed pores and allow to give the piece a shiny black aspect bluish reflection of the anti-corrosion treatment. At the outlet of the treatment bath, the part has thus acquired durable anticorrosive properties. The advantage of this method is that it can be applied multiple times on the same piece, without the need to return this piece to bare.

According to another characteristic, the treatment bath contains, in addition per liter of solution, 0.1 to 0.5 g of at least one antioxidant agent which may, advantageously but in a nonlimiting manner of the invention, consist of hexamethylene tetramine.

Such an antioxidant makes it possible to increase the efficiency of the reaction by avoiding, in particular, the formation of oxide during the treatment. The agent makes it possible to neutralize the oxygen and hydrogen that may form in the treatment bath.

In certain particular cases, hexamethylenetetramine may be associated and / or replaced by natural aromatic essences which, in addition to marked antioxidant properties, have the advantage of neutralizing the odors of the gases escaping from the treatment bath and from make it less aggressive.

According to another characteristic, the treatment bath comprises, moreover, per liter of solution, between 5 and 25 g of at least one bonding agent making it possible to improve the contact between the various constituents of the bath and consequently to increase the reaction rate. It is possible, for this purpose, to use ammonium chloride, if appropriate, associated or replaced by sodium thiosulfate. 5.2. Implementation system.

The present technique can be implemented in an anticorrosion treatment system comprising a plurality of tanks each containing a bath associated with one or more steps of the method described above. Such a system may be in the form of a tank alignment, overhung by a piece transport mechanism, said mechanism being robotic or manual. Depending on the respective processing times, an electronic device controls the implementation of the processing. Such an electronic device is able to actuate one or more elevators of the mechanism to recover for example a submerged part and deposit this piece in the next tank of the treatment.

In a complementary manner, one or more tanks is equipped with a measurement probe. Such a measurement probe is able to measure at least some parameters of the bath of the tank in order to finish, on the basis of the data received from the probe, if the characteristics of the bath are clean to allow a correct treatment of the piece in the bath considered. Cleverly, the probe is an optical probe, one of the characteristics of which is to allow a measure of opacity and / or colorimetry of the bath to determine whether it is specific to the treatment under consideration. The advantage of such an optical probe is that it can be inserted in a transparent structure resistant to the action of the chemicals used in the treatment previously described and that it therefore not deteriorated during treatment. 5.3. Other features and benefits

In connection with FIG. 3, an electronic control device, controlling a processing system such as the one presented above, is described. Such a device is configured to implement an anticorrosion treatment according to the anticorrosion treatment method described previously.

For example, the device comprises a memory 31 consisting of a buffer memory, a processing unit 32, equipped for example with a microprocessor, and driven by the computer program 33, implementing an anticorrosion treatment process. At initialization, the code instructions of the computer program 33 are for example loaded into a memory before being executed by the processor of the processing unit 32. The processing unit 32 receives as input at least one piece of data. a duration of treatment. The microprocessor of the processing unit 32 implements the steps of the processing method, according to the instructions of the computer program 33 to control the immersion times of the part in the different baths of the treatment.

For this, the device comprises, in addition to the buffer memory 31, time control means. Depending on the embodiments, such a device also comprises means for receiving, from probes placed in the tanks, data representative of the state of the different treatment baths. Depending on these data, the device is able to transmit one or more bath change messages. These messages indicate the tank or tanks in which the baths are no longer able to perform the expected functions.

Claims (7)

1) A method of anticorrosion treatment characterized in thatii comprises a step of anticorrosion treatment of a workpiece, iadite processing step (T02) of dipping said piece, for a period of between 10 and 20 minutes, in a treatment bath comprising per liter, 560 and 660 g of alkali hydroxides, between 75 and 95 g of nitrates and / or of alkaline nitrite, between 75 and 95 g of borax and 40 g of at least one surfactant this bath being heated to a temperature of between 130 and 160 ° C. 2) A method of anticorrosion treatment, according to claim 1, characterized in that it further comprises, prior to said anticorrosive treatment step, a pretreatment step (PO1) anticorrosion of said workpiece, said pretreatment step consisting of immersing said part, for a period of between 10 and 20 minutes, in a treatment bath comprising, per liter of solution, 630 and 770 g of alkaline hydroxides, between 60 and 80 g of nitrates and / or of alkaline nitrites, between 60 and 80 g of borax, this bath being brought to a temperature between 130 and 160 ° C. 3) Process of treatment according to claim 2, characterized in that it further comprises a preliminary step of preparation (OOP) of said part, said preparation step comprising at least one degreasing step and at least one stripping step. 4) Process of treatment according to claim 3, characterized in that said preliminary step of preparation (POO) of said part, said preparation step comprises: a pre-degreasing step (POOl) of the workpiece, comprising the setting use of an alkaline pre-degreasing solution, at a temperature between 65 ° C and 75 ° C, for a period of between 10 and 20 minutes; a step of degreasing (P002) the workpiece, comprising the implementation of an alkaline degreasing solution, at a temperature between 65 ° C and 75 ° C, for a period of between 10 and 20 minutes; a rinsing step (P003), with water, at a temperature between 65 and 75 ° C, for a period of between 5 and 10 minutes; at least one rinsing step (P004) at room temperature for 2 to 5 minutes; a pickling step (P005) in a solution of hydrochloric acid diluted between 30 and 35% for a period of between 10 and 20 minutes; at least one rinsing step (P006) at room temperature for 2 to 5 minutes. 5) Anti-corrosion treatment system characterized in that it comprises an anticorrosion treatment tank of at least one workpiece, said treatment tank comprising a treatment bath comprising per liter of solution, 560 and 660 g of alkali hydroxides between 75 and 95 g of nitrates and / or of alkaline nitrite, between 75 and 95 g of borax and 40 g of at least one surfactant, this bath being brought to a temperature of between 130 and 160 ° C., within which the piece to be treated takes place for a period of between 10 and 20 minutes. 6) anti-corrosion treatment system according to claim 5, characterized in that it comprises a tank anticorrosion pretreatment of said workpiece, said treatment tank comprising a pretreatment bath comprising per liter of solution, 630 and 770 g of alkali hydroxides, between 60 and 80 g of nitrates and / or of alkaline nitrites, between 60 and 80 g of borax, this bath being brought to a temperature of between 130 and 160 ° C., bath in which the workpiece takes place for a period of between 10 and 20 minutes. 7) Computer program product downloadable from a communication network and / or stored on a computer readable medium and / or executable by a microprocessor, characterized in that it comprises program code instructions for the execution of a processing method according to claim 1, within a processing system, when executed on a processor.