Abstract
The present invention discloses a method for the controlled guidance of corrosion by the action of a laser beam. This method enables the selective adjustment of the speed of corrosion in each area of a target component and, therefore, the driving of the corrosion towards the areas of interest. With the application of this method, the corrosion process is guided by the laser treatment and becomes predictable and controllable. The method is applicable in all those sectors of activity where it is necessary to control corrosion.
Claims
1. Method for the controlled guidance of corrosion on a material or article to be treated comprising the following steps: providing a guidance strategy for guiding corrosion on the material or article to be treated, said guidance strategy for guiding corrosion comprising a map with guidance directions for guiding corrosion; establishing at least one laser beam surface treatment to be applied on the material or article to be treated by means of an increasing exposure, providing at least two speeds of corrosion in the material or article to be treated; applying said at least one laser beam surface treatment on at least one area of the material or article to be treated with an increasing exposure in the direction indicated by the aforementioned map with guidance directions.
2. A method according to claim 1, wherein the increasing exposure corresponds to the formula
=ln/{square root over ()} wherein P is the power of the laser, and v is the processing speed.
3. A method according to any of the preceding claims comprising a plurality of laser beam surface treatments performed with an increase in the exposure in defined stages, preferably two stages, and more preferably four stages.
4. A method according to any of claim 1 or 2, wherein the at least one surface treatment is performed by means of a gradual increase in exposure.
5. A method according to claim 1, wherein, in the step of establishing at least one laser beam surface treatment on the material or article to be treated, said laser beam comes from a laser source the wavelength of which is within the range of 100 nm to 11000 nm.
6. A method according to claim 1, wherein the mean power of the laser source is within the range of 1 W to 5000 W.
7. A method according to claim 1, wherein the laser source used to generate laser beam radiation is selected from Nd:YAG, Nd:glass, Nd:YVO.sub.4, Er:YAG, Yb:YAG, Tm:YAG, diode, fiber, disk, CO.sub.2, CO, HeCd, copper vapor, iodine, argon, krypton lasers or chemical lasers (HF, DF).
8. A method according to claim 1, wherein the laser source used emits radiation in pulsed or continuous mode.
9. A method according to any of claims 5 to 8, wherein the laser source used emits in pulsed mode with a pulse duration between milliseconds and femtoseconds and more favorably in the range of 1 to 500 nanoseconds.
10. A method according to claim 1, wherein the material or article to be treated has a non-planar shape and the laser beam scans the surface of the material or article to be treated by means of a three-dimensional optical scanning system.
11. A method according to claim 1, wherein the material or article to be treated has a planar shape and the laser beam scans the surface of the material or article to be treated by means of a two-dimensional optical scanning system.
12. A method according to claim 1, wherein the method is carried out in a vacuum or in the presence of an oxidizing gas atmosphere.
13. A method according to claim 12, wherein the oxidizing gas is O.sub.2, CO.sub.2, or mixtures thereof.
14. Use of the method according to the preceding claims for the manufacture of a resorbable metallic osteosynthesis plate that can be reabsorbed by the human body.
15. Use of the method according to claims 1 to 8 for the manufacture of an anode for the cathodic protection of steel reinforcements in constructions made of concrete with guided and controlled corrosion, having a prolonged duration and protection.
Description
DESCRIPTION OF THE DRAWINGS
[0042] To complement the description that is being made and for the purpose of helping to better understand the features of the invention, the following figures are attached as an integral part of said description.
[0043] FIG. 1: this figure schematically depicts four types of treatments performed on a material or article to be treated according to one embodiment of the invention.
[0044] FIG. 2: this figure shows a guidance strategy for guiding corrosion on a material or article to be treated according to one embodiment of the invention, such that a direction for guiding the corrosion following the direction of the arrow is defined.
[0045] FIG. 3: this figure shows a guidance strategy for guiding corrosion on a material or article to be treated according to another embodiment of the invention, such that a direction for guiding the corrosion following the direction of the arrow is defined.
[0046] FIGS. 4a to 4e: these figures show the uncontrolled temporal evolution of a magnesium alloy plate subjected to corrosion in physiological saline solution, FIG. 4a corresponding to the article before the start of the test and successive FIGS. 4b to 4e to the random evolution of the corrosion of the article over 3 weeks.
[0047] FIGS. 5a to 5e: these figures show the controlled temporal evolution of a magnesium alloy plate subjected to corrosion in physiological saline solution to which the guidance strategy according to the embodiment of FIG. 2 has been applied. FIG. 5a shows the article before the start of the corrosion test, whereas successive FIGS. 5b to 5e show the controlled or guided evolution of the same article over 3 weeks.
[0048] FIGS. 6a to 6e: these figures show the controlled temporal evolution of a magnesium alloy plate subjected to corrosion in physiological saline solution to which the guidance strategy according to the embodiment of FIG. 3 has been applied. FIG. 6a shows the article before the start of the corrosion test, whereas successive FIGS. 6b to 6e show the controlled or guided evolution of the same article over 3 weeks.
[0049] FIGS. 7a to 7e: these figures show the controlled temporal evolution of a magnesium alloy plate subjected to corrosion in physiological saline solution to which a guidance strategy according to another embodiment of the invention in which the central diamond shape has been treated with high exposure (equivalent to treatment T4 of the embodiment of FIG. 1) and the rest of the article has been treated with low exposure (equivalent to treatment T1 of the embodiment of FIG. 1) has been applied. FIG. 7a shows the article before the start of the corrosion test, whereas successive FIGS. 7b to 7e show the controlled or guided evolution of the same article over 3 weeks.
[0050] FIGS. 8a to 8b: these figures show the controlled temporal evolution of a magnesium alloy plate subjected to corrosion in physiological saline solution to which a guidance strategy according to another embodiment of the invention in which the central diamond shape has been treated with low exposure (equivalent to treatment T1 of the embodiment of FIG. 1) and the rest of the article has been treated with high exposure (equivalent to treatment T4 of the embodiment of FIG. 1) has been applied. FIG. 8a shows the article before the start of the corrosion test, whereas FIG. 8b shows the state of the same article after 3 weeks.
[0051] FIGS. 9a to 9b: these figures show the controlled temporal evolution of a magnesium alloy plate subjected to corrosion in physiological saline solution to which a guidance strategy according to another embodiment of the invention in which the central diamond shape and the triangles of the four corners of the article have been treated with low exposure (equivalent to treatment T1 of the embodiment of FIG. 1) and the rest of the article has been treated with high exposure (equivalent to treatment T4 of the embodiment of FIG. 1) has been applied. FIG. 9a shows the article before the start of the corrosion test, whereas FIG. 9b shows the state of the same article after 3 weeks.
[0052] FIGS. 10a to 10l: these figures show the application of the method object of the invention according to a particular embodiment to the manufacture of biodegradable osteosynthesis plates.
[0053] FIGS. 11a to 11h: these figures show the application of the method object of the invention according to a particular embodiment for the manufacture of anodes for the cathodic protection of steel reinforcements in constructions made of concrete.
DETAILED DISCLOSURE OF THE INVENTION
[0054] The present invention relates to a method for the controlled guidance of corrosion on a material or article to be treated.
[0055] FIG. 1 schematically depicts four types of treatment performed by means of a laser beam on a material or article to be treated. The difference between the treatments lies in the different exposure. In that sense, the exposure in treatment T1 is lower than in treatment T2, the exposure in treatment T2 is lower than in treatment T3, and the exposure in treatment T3 is lower than in treatment T4. Therefore, the speed of corrosion of a material subjected to treatment T1 is higher than the speed of corrosion of the same material subjected to treatment T2. In turn, the speed of corrosion of this material subjected to treatment T2 is higher than the speed of corrosion of the same material subjected to treatment T3, and the speed of corrosion of this material subjected to treatment T3 is higher than the speed of corrosion of the same material subjected to treatment T4.
[0056] FIG. 2 shows an exemplary guidance strategy for guiding corrosion on a material or article to be treated, such that a direction for guiding the corrosion following the direction of the arrow is defined. The four different areas correspond to laser treatments performed with different exposures on the surface of the material or article to be treated. Therefore, the exposure is an increasing exposure according to the following guideline: exposure in T1 is higher than the exposure in T2; the exposure in T2 is higher than the exposure in T3; and the exposure in T3 is higher than the exposure in T4.
[0057] FIG. 3 shows an exemplary guidance strategy for guiding corrosion on a material or article to be treated, such that a direction for guiding the corrosion following the direction of the arrow is defined. In this case, the exposure of the laser beam on the material or article to be treated increases gradually in the direction of the arrow.
[0058] FIG. 4 shows the temporal evolution of an AZ31 magnesium alloy plate subjected to corrosion in physiological saline solution (normal saline solution, containing 9 grams per liter of ClNa). FIG. 4a shows the article before the start of the corrosion test, whereas successive FIGS. 4b, 4c, 4d, and 4e show the evolution of the same article over 3 weeks. It can be seen that corrosion occurs in a random, unpredictable manner, causing aggression on the article in all directions. After 3 weeks, the article is completely destroyed.
[0059] FIG. 5 shows the temporal evolution of an AZ31 magnesium alloy plate subjected to corrosion in physiological saline solution (normal saline solution, containing 9 grams per liter of ClNa), to which the method of controlled corrosion guidance object of the present invention has been applied. This case follows the strategy shown in FIG. 2. FIG. 5a shows the article before the start of the corrosion test, whereas successive FIGS. 5b, 5c, 5d, and 5e show the evolution of the same article over 3 weeks. It can be seen that corrosion occurs in a guided or controlled manner, starting at the lower part of the article and progressing towards the upper part, following the direction established by the method of guiding object of the present invention. After 3 weeks, the article has not corroded in its entirety.
[0060] FIG. 6 shows the temporal evolution of a magnesium alloy plate subjected to corrosion in physiological saline solution (normal saline solution, containing 9 grams per liter of ClNa), to which the method of controlled corrosion guidance object of the present invention has been applied. This case follows the strategy shown in FIG. 3. FIG. 6a shows the article before the start of the corrosion test, whereas successive FIGS. 6b, 6c, 6d, and 6e show the evolution of the same article over 3 weeks. It can be seen that corrosion occurs in a guided or controlled manner, starting at the lower part of the article and progressing towards the upper part, following the direction established by the method of guiding object of the present invention. After 3 weeks, corrosion reached only a little more than half of the article.
[0061] FIG. 7 shows the temporal evolution of a magnesium alloy plate subjected to corrosion in physiological saline solution (normal saline solution, containing 9 grams per liter of ClNa), to which the method of controlled corrosion guidance object of the present invention has been applied. In this case, the central diamond shape has been treated with high exposure (equivalent to treatment T4 of the embodiment of FIG. 1) and the rest of the article has been treated with low exposure (equivalent to treatment T1 of the embodiment of FIG. 1). FIG. 7a shows the article before the start of the corrosion test, whereas successive FIGS. 7b, 7c, 7d, and 7e show the evolution of the same article over 3 weeks. It can be seen that corrosion occurs in a guided or controlled manner, starting at the periphery of the article and progressing towards the center thereof. After 3 weeks, the central diamond shape has not been corroded.
[0062] FIG. 8 shows the temporal evolution of a magnesium alloy plate subjected to corrosion in physiological saline solution (normal saline solution, containing 9 grams per liter of ClNa), to which the method of controlled corrosion guidance object of the present invention has been applied. In this case, the central diamond shape has been treated with low exposure (equivalent to treatment T1 of the embodiment of FIG. 1) and the rest of the article has been treated with high exposure (equivalent to treatment T4 of the embodiment of FIG. 1). FIG. 8a shows the article before the start of the corrosion test, whereas FIG. 8b shows the state of the same article after 3 weeks. It can be seen that corrosion occurs in a guided or controlled manner, starting in the interior of the article and progressing towards the periphery thereof. After 3 weeks, corrosion has only affected the central diamond shape.
[0063] FIG. 9 shows the temporal evolution of a magnesium alloy plate subjected to corrosion in physiological saline solution (normal saline solution, containing 9 grams per liter of ClNa), to which the method of controlled corrosion guidance object of the present invention has been applied. In this case, the central diamond shape and the triangles of the four corners of the article have been treated with low exposure (equivalent to treatment T1 of the embodiment of FIG. 1) and the rest of the article has been treated with high exposure (equivalent to treatment T4 of the embodiment of FIG. 1). FIG. 9a shows the article before the start of the corrosion test, whereas FIG. 9b shows the state of the same article after 3 weeks. It can be seen that corrosion occurs in a guided or controlled manner, starting in the interior and in the four corners of the article and progressing towards the areas treated with treatment type T4. After 3 weeks, corrosion has only affected the four corners and the central diamond shape.
[0064] FIG. 10 shows the application of the method object of the invention to the manufacture of biodegradable osteosynthesis plates. FIGS. 10a, 10b, 10c, and 10d show the evolution in the regeneration of a bone fracture by means of a non-resorbable metallic osteosynthesis plate. When the bone has already been regenerated (FIG. 10d), the osteosynthesis plate is still intact and a second surgical operation is required to return the patient to his or her initial condition, i.e., with the regenerated bone but without a metal plate inside his or her body. FIGS. 10e, 10f, 10g, and 10h show the same process as in the previous figures, but now using a plate made of a resorbable material. This material loses its mechanical integrity before complete bone regeneration (FIG. 10f), so the bone is not properly regenerated (FIG. 10h). FIGS. 10i, 10j, 10k, and 10l show the same process as in the two previous cases, but now using an osteosynthesis plate made of a resorbable magnesium alloy but subjected to the method of controlled corrosion guidance object of the present invention. In this case, corrosion occurs in a guided or controlled manner and at the same rate at which the bone regenerates (FIG. 10j and FIG. 10k). The result is complete bone regeneration and complete resorption of the osteosynthesis plate (FIG. 10l). This means full recovery of bone functionality and avoiding a second operation to remove the osteosynthesis plate.
[0065] FIG. 11 shows the application of the method object of the present invention for the manufacture of anodes for the cathodic protection of steel reinforcements in constructions made of concrete. FIGS. 11a, 11b, 11c, and 11d show the behavior of reinforced concrete when an anode is used for conventional cathodic protection. The anode undergoes an uncontrolled corrosion process. As a result, its service life is short and it ceases to protect the reinforcements from corrosion (FIG. 11c), so a layer of corrosion products is formed on the reinforcements which strain and crack the concrete, causing its structural failure (FIG. 11d).
[0066] When the anode for cathodic protection is subjected to the method object of the present invention, corrosion occurs in a guided or controlled manner, so the anode corrodes slowly (FIG. 11g), whereby very notably increasing its service life and extending the time of duration of the cathodic protection (FIG. 11h). The final result is a longer service life of the constructions made of reinforced concrete.
EXAMPLES
Example 1
[0067] To guide corrosion in an AZ31 magnesium alloy plate, a guidance strategy consisting of the corrosion having to start at the bottom part of the plate and progress towards the upper part thereof was established.
[0068] A set of laser surface treatments was established, with a Nd:YVO4 laser beam (1064 nm) with a rated power of 20 W being used, operating in pulsed mode with a 20-ns pulse duration and focused on the surface of an AZ31 magnesium alloy plate. With this laser and this material, four different treatments called T1, T2, T3, and T4 were established, and they gave rise to four different speeds of corrosion, with the speed of corrosion being higher in treatment T1 than in T2, the speed of corrosion being higher in T2 than in T3, and the speed of corrosion being higher in T3 than in T4.
[0069] The values of increasing exposure of the AZ31 magnesium alloy to the action of the laser beam, increasing exposure being understood to mean the Napierian logarithm of the quotient of the power of the laser squared, divided by the square root of the processing speed,
=ln/{square root over ()}
were the following for each treatment:
[00001]
[0070] A treatment was then performed with increasing exposure in stages as shown in FIG. 2. Once the article made of AZ31 magnesium alloy was treated, a corrosion test in physiological saline solution was performed on an untreated AZ31 magnesium alloy plate (FIG. 4) and the article made of magnesium alloy to which the method object of the invention that was just described in detail was applied (FIG. 5).
[0071] As can be seen by comparing FIGS. 4 and 5, it can be seen that, in the untreated article in all directions (FIG. 4). After 3 weeks, the article is completely destroyed. However, in the article to which the method object of the present invention has been applied, according to the present embodiment, guidance of corrosion from top to bottom of the article, following the initially established direction (FIG. 5), can be observed. After 3 weeks, the article has not corroded in its entirety.
Example 2
[0072] To guide corrosion in an AZ31 magnesium alloy plate, a guidance strategy consisting of the corrosion having to start at the bottom part of the plate and progress towards the upper part thereof was established.
[0073] A set of laser surface treatments was established, with a Nd:YVO4 laser beam (1064 nm) with a rated power of 20 W being used, operating in pulsed mode with a 20-ns pulse duration and focused on the surface of an AZ31 magnesium alloy plate. With this laser and this material, different treatments which gave rise to different speeds of corrosion were established. These treatments successfully changed the value of exposure of the AZ31 magnesium alloy to the action of the laser beam.
[0074] The values of increasing exposure of the AZ31 magnesium alloy to the action of the laser beam, increasing exposure being understood to mean the Napierian logarithm of the quotient of the power of the laser squared, divided by the square root of the processing speed,
=ln/{square root over ()}
were gradually increased from a value of 2.2 W.sup.2 m.sup.0.5 s.sup.0.5 to a maximum value of 6.0 W.sup.2 m.sup.0.5 s.sup.0.5.
[0075] A treatment was then performed with the gradually increasing exposure as shown in FIG. 3. Once the article made of AZ31 magnesium alloy has been treated, a corrosion test in physiological saline solution was performed on an untreated AZ31 magnesium alloy plate (FIG. 4) and the article made of magnesium alloy to which the method object of the invention that was just described in detail was applied (FIG. 6).
[0076] As can be seen by comparing FIGS. 4 and 6, it can be seen that, in the untreated article in all directions (FIG. 4). After 3 weeks, the article is completely destroyed. However, in the article to which the method object of the present invention has been applied, according to the present embodiment, guidance of the corrosion from top to bottom of the article, following the initially established direction (FIG. 6), can be observed. After 3 weeks, corrosion reached only a little more than half of the article.
Example 3
[0077] To guide corrosion in an AZ31 magnesium alloy plate, a guidance strategy consisting of the corrosion having to start in the periphery of the article and progress towards the center thereof was established.
[0078] A set of laser surface treatments was established, with a Nd:YVO4 laser beam (1064 nm) with a rated power of 20 W being used, operating in pulsed mode with a 20-ns pulse duration and focused on the surface of an AZ31 magnesium alloy plate. With this laser and this material, two different treatments which gave rise to two different speeds of corrosion, with the speed of corrosion being higher in the first treatment than in the second treatment, were established.
[0079] The values of increasing exposure of the AZ31 magnesium alloy to the action of the laser beam, increasing exposure being understood to mean the Napierian logarithm of the quotient of the power of the laser squared, divided by the square root of the processing speed,
=ln/{square root over ()}
were 0 W.sup.2 m.sup.0.5 s.sup.0.5 for the first treatment and 6.0 W.sup.2 m.sup.0.5 s.sup.0.5 for the second treatment.
[0080] In this case, the central diamond shape was subjected to the second treatment and the rest of the article to the first treatment. Once the article made of AZ31 magnesium alloy has been treated, a corrosion test in physiological saline solution was performed on an untreated AZ31 magnesium alloy plate (FIG. 4) and the article made of magnesium alloy to which the method object of the invention that was just described in detail was applied (FIG. 7).
[0081] As can be seen by comparing FIGS. 4 and 7, it can be seen that, in the untreated article in all directions (FIG. 4). After 3 weeks, the article is completely destroyed. However, in the article to which the method object of the present invention has been applied, according to the present embodiment, guidance of the corrosion from the periphery towards the interior, following the initially established direction (FIG. 7), can be observed. After 3 weeks, the central diamond shape has not been corroded.
Example 4
[0082] This example is the result of applying the method object of the present invention according to the embodiment of Example 3, i.e., with the same material, with the same laser, and with the same values of increasing exposure as in said Example 3, but with the exception that in this Example 4, a guidance strategy for guiding corrosion such that corrosion must start at the center of the plate and progress towards the periphery is established.
[0083] It can be seen in FIG. 8 that corrosion occurs in a guided manner, starting in the interior of the article and progressing towards the periphery thereof. After 3 weeks, corrosion has only affected the central diamond shape.
Example 5
[0084] This example is the result of applying the method object of the present invention according to the embodiment of Example 3, i.e., with the same material, with the same laser, and with the same values of increasing exposure as in said Example 3, but with the exception that in this Example 5, a guidance strategy for guiding corrosion such that corrosion must be directed from the corners towards the center of the plate and from the center of the plate towards the corners is established.
[0085] It can be seen in FIG. 9 that corrosion occurs in a guided manner, starting in the four corners and in the interior of the article and progressing towards the interior and towards the corners, respectively. After 3 weeks, corrosion has only affected the four corners and the central diamond shape.
[0086] Having sufficiently described the nature of the present invention, as well as the way of carrying it out to practice, it only remains to be added that it is possible to introduce in said invention, as a whole and in its constituent parts, changes in form, materials, and arrangement, provided that such alterations do not substantially change said invention.
