METHOD FOR MONITORING A PART VIA COLORIMETRY

Abstract

A method of fabricating and inspecting a part, the method including the following steps a) treating a substrate including aluminum by a chemical conversion method making use of a treatment solution including chromium with a degree of oxidation of +III in order to obtain a part presenting a chemical conversion layer; and b) inspecting the presence of the chemical conversion layer obtained during step a) by using a colorimeter to measure the color of the chemical conversion layer and by comparing the measured color with a reference color.

Claims

1. A method of fabricating and inspecting a part, the method comprising the following steps: a) treating a substrate including aluminum by a chemical conversion method making use of a treatment solution including chromium with a degree of oxidation of +III in order to obtain a part presenting a chemical conversion layer; and b) inspecting the a presence of the chemical conversion layer obtained during step a) by using a colorimeter to measure the color of said chemical conversion layer and by comparing the measured color with a reference color.

2. A method according to claim 1, wherein an initial anodic oxidation or chemical conversion coating is formed on the substrate before step a), and wherein the chemical conversion layer obtained during step a) is adjacent to the initial coating.

3. A method according to claim 1, wherein the chemical conversion treatment performed during step a) is a reworking operation during which the treatment solution is applied locally on the substrate by means of an applicator.

4. A method according to any one of claims 1, wherein the colorimeter is in the form of a handheld tool.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Other characteristics and advantages of the invention appear from the following description of particular implementations of the invention, given as nonlimiting examples, and with reference to the accompanying drawing, in which:

[0032] FIG. 1 shows in a highly diagrammatic and fragmentary manner a plan view of an example of a part obtained after performing a step a) of the invention; and

[0033] FIG. 2 shows in a highly diagrammatic and fragmentary manner a plan view of another example of a part obtained after performing a step a) of the invention.

EXAMPLES

Example 1

Step a) Performed After Making an Initial Coating by Chemical Conversion

[0034] In this example, a substrate made of aluminum alloy 5086 was initially coated with an initial coating obtained by immersing the substrate in a SurTec° 650 treatment solution.

[0035] Thereafter, a step a) of the invention was performed wherein reworking chemical conversion treatment was performed after the initial coating had been formed. The treatment solution used during this step a) is sold under the name SurTec® 650 and it was applied by means of a stick.

[0036] A zone adjacent to the zone treated by the reworking treatment was left cleaned.

[0037] FIG. 1 is a very diagrammatic plan view of the part 1 obtained in that way. In this figure, the initial coating is represented by the symbol 2, the zone reworked by chemical conversion by the symbol 3, and the stripped zone by the symbol 4. As shown, the chemical conversion layer 3 obtained during step a) is adjacent to the initial coating 2, with the initial coating 2 surrounding the layer 3.

[0038] To the naked eye, the reworked zone 3 and the stripped zone 4 are very difficult to distinguish from each other.

[0039] The measurements of step b) were performed using a Konica Minolta CM-700d colorimeter in specular component included (SCI) mode. The CIE Lab color space was used.

[0040] As shown in FIG. 1, for each of the zones in which color was measured during step b), the L*, a*, and b* coordinates were measured at five points in each of these zones, with the results obtained then being averaged over those five points (arithmetic mean) in order to determine the color of the zone in question. FIG. 1 shows diagrammatically the measurement points A of the zone 3 reworked by chemical conversion and the measurement points B of the stripped zone 4.

[0041] Initially, the color of the reference zone was evaluated, this color corresponding to the reference color. The reference zone corresponds to a reference chemical conversion layer formed in accordance with step a) of the present example, i.e. on a 5086 alloy and by using the same chemical conversion treatment.

[0042] A reference color was obtained after calculating an average over the five measurement points, and it presented the color coordinates given in detail in Table 1 below.

TABLE-US-00001 TABLE 1 L* a* b* Reference color 84.12 0.09 −2.09

[0043] Thereafter, the colors of the chemical conversion layer obtained during step a) and of the stripped zone were measured.

[0044] A color was obtained for each of these zones by calculating an average over five measurement points, and they presented the results set out in Table 2 below. For each of these two zones, the color differences relative to the reference color are given in the column ΔE*ab.

TABLE-US-00002 TABLE 2 L* a* b* ΔE*ab Stripped zone 88.89 −0.05 0.64 5.50 Chemical conversion 83.69 0.14 −1.56 0.69 layer obtained during step a)

[0045] A significant color difference was obtained between the color of the stripped zone and the reference color (5.50), which shows that the method of the invention makes it possible to distinguish between two different surfaces even though they are similar in appearance to the naked eye. Also, the color difference between the color of the chemical conversion layer obtained during step a) and the reference color is small (0.69). Such a color difference value serves to confirm that step a) was performed correctly.

Example 2

Step a) Performed After Making an Initial Coating by Anodization

[0046] In this example, a substrate made of aluminum 7010 alloy was initially coated by an initial coating obtained by chromium acid anodizing using chromium with degree of oxidation +VI.

[0047] Thereafter, a step a) of the invention was performed wherein reworking chemical conversion treatment was performed after the initial coating had been formed. The treatment solution used during this step a) is sold under the name SurTec® 650 and it was applied by means of a stick.

[0048] A zone distinct from the zone treated by the reworking treatment was stripped.

[0049] FIG. 2 is a very diagrammatic plan view of the part 10 obtained in that way. In this figure, the initial coating is represented by the symbol 20, the zone reworked by chemical conversion by the symbol 30, and the stripped zone by the symbol 40. As shown, the chemical conversion layer 30 obtained during step a) is adjacent to the initial coating 20, with the initial coating 20 surrounding the layer 30.

[0050] To the naked eye, the reworked and stripped zones are very difficult to distinguish from each other.

[0051] The measurements of step b) were performed using a Konica Minolta CM-700d colorimeter in specular component included (SCI) mode. The CIE Lab color space was used.

[0052] As shown in FIG. 2, for each of the zones in which color was measured during step b), the L*, a*, and b* coordinates were measured at five points in each of these zones, with the results obtained then being averaged over those five points (arithmetic mean) in order to determine the color of the zone in question. FIG. 2 shows diagrammatically the measurement points A of the zone 30 reworked by chemical conversion and the measurement points B of the stripped zone 40.

[0053] Initially, the color of the reference zone was evaluated, this color corresponding to the reference color. The reference zone corresponds to a reference chemical conversion layer formed in accordance with step a) of the present example, i.e. on a 7010 alloy and by using the same chemical conversion treatment.

[0054] A reference color was obtained after calculating an average over the five measurement points, and it presented the color coordinates given in detail in Table 3 below.

TABLE-US-00003 TABLE 3 L* a* b* Reference color 81.57 0.24 −1.64

[0055] Thereafter, the colors of the chemical conversion layer obtained during step a) and of the stripped zone were measured.

[0056] A color was obtained for each of these zones by calculating an average over five measurement points, and they presented the results set out in Table 4 below. For each of these two zones, the color differences relative to the reference color are given in the columns ΔE*ab.

TABLE-US-00004 TABLE 4 L* a* b* ΔE*ab Stripped zone 78.79 −0.01 0.86 3.74 Chemical conversion 82.50 0.35 −1.28 1.00 layer obtained during step a)

[0057] A significant color difference was obtained between the color of the stripped zone and the reference color (3.74), which means that the surfaces are different. Also,, the color difference measured between the color of the chemical conversion layer obtained during step a) and the reference color is small (1.00). Such a color difference value serves to confirm that step a) was performed correctly.

[0058] The term “including/containing/comprising a” should be understood as “including/containing/comprising at least one”.

[0059] The term “lying in the range . . . to . . .” should be understood as including the limits.