RU2814783C1 - Method for gradient colouring of full surface of article made from alloys of titanium, tantalum, zirconium, niobium, hafnium, tungsten or part thereof with possibility of colour skipping - Google Patents

Abstract

FIELD: electrochemistry.

SUBSTANCE: invention relates to electrochemistry and specifically to a method of producing a decorative gradient coating. To obtain a coloured gradient coating with more than two colour transitions for each created colour, the voltage region of the created gradient U_start, U_end and calculating the stress of the defect area of the gradient — colour skip areas U_def1, U_def2 according to the formula U_def1,2=(U_end – U_start)/k, where U_start is lowest voltage used when creating gradient at initial stage of anodizing, U_end is highest voltage used when creating gradient at final stage of anodizing, U_def1 is lowest voltage at which a defect area in the gradient is observed, U_def2 is highest voltage at which a defect area in the gradient is observed, k is coefficient used to calculate the skip area — defect for gradients with colour transitions more than two times k=1;1.3, then the product is degreased, a preliminary oxide film is formed, created by anodizing at the initial stage of forming a gradient at voltage U_start, and the decorative coloured gradient coating is obtained by anodizing, which is carried out by smoothly removing the article from the electrolyte with simultaneous increase in the voltage value, at that, when U_def1 is reached and up to U_def2, holding the created colour until the current density drops to 0.1 A/dm² and changing the level of immersion of the article in the electrolyte, and after reaching U_def2, the previous holding parameters are used and the article is gradually removed from the electrolyte.

EFFECT: obtaining gradient interference films with and without colour skipping, characterized by high quality of porous oxide due to elimination of defects.

1 cl, 2 dwg, 2 tbl, 1 ex

Description

The invention relates to the field of electrochemistry, namely to the electrochemical production of a gradient anodic oxide film on the full surface of a product made of alloys of titanium, tantalum, zirconium, niobium, hafnium, tungsten or part thereof by applying a gradient anodic oxide film by smoothly removing the product from the electrolyte with a simultaneous increase voltage values and the ability to skip color (it is possible to obtain a gradient with or without skipping color).

The proposed method can be used for decorative coating of the full surface of a product made of titanium, tantalum, zirconium, niobium, hafnium, tungsten alloys or parts thereof in gradients of different colors. For this method, firstly, it is possible to create color transitions that replace each other due to a consistent increase in voltage (Table 1). Secondly, it is possible to create a color skip in a sequence of color transitions defined by increasing the voltage value (Table 1).

Table 1 - The order of color changes with a sequential increase in voltage, at the concentration of the electrolyte giving maximum color saturation

Color sequence number with sequential increase in voltage Color Voltage corresponding to color 1 2 3 1 Yellow (warm) 7V 2 Brown 12V 3 Burgundy 15V 4 Violet 19V

Continuation of Table 1

1 2 3 5 Blue (cold) 25V 6 Blue 30V 7 Light blue 40V 8 Light yellow (cold) 50V 9 Yellow (cold) 55V 10 Orange 60V eleven Crimson 70V 12 Blue (warm) 85V 13 Green 95V

The scope of application is wide: painting of vehicle bodies, watches, telephones; jewelry and costume jewelry; interior and exterior elements; implants and much more.

There is a known method for obtaining a color image on metal surfaces [RU 2357844 C2 Method for obtaining a color image on metal surfaces, Mikhail Grigorievich Afonkin, Vladimir Borisovich Zvyagin, Ekaterina Vladimirovna Larionova, Evgeniy Ivanovich Priyakhin, 2009.06.10], due to the formation of nanostructures in the form of oxide films, formed as a result of local heating by a pulsed heat source (for example, laser radiation, plasma, electric contact or other type of heating). The invention makes it possible to apply a color image to any metal surface without preliminary processing and without preliminary construction of calibration curves. The disadvantages of this method are complex preliminary mathematical calculations, high cost, color transitions are possible, but their smoothness, saturation, and possible increase in defects when applying gradients of several colors are not taken into account.

The closest analogue of the proposed method is a method for obtaining a pattern on aluminum material, according to which a protective film is applied to the aluminum surface after electrolytic painting, forming the required pattern, using a composition containing alkyd resin, methylcellulose and polyvinyl butyral. Then, areas of the aluminum surface without a protective film are electrolytically painted in a different color to obtain a two-color pattern on the aluminum surface. [A.z. Japan N 62-60480, publ. 12/16/87] The advantages of this method are that it allows you to apply films to the entire surface and to part of it; the method is quite economical compared to local heating methods, and also does not require preliminary calculations or the construction of calibration curves. The disadvantage of this method is that the applied films are only monochromatic; gradient application, which requires a special technique, is not taken into account.

In both methods, the features of applying gradient films are not taken into account, or gradient films are not assumed at all. The electrochemical method has a number of advantages: relative low cost and technological simplicity (preliminary calculations and construction of calibration curves are not required); the possibility of implementation, both in production and independently in artisanal conditions, while observing safety precautions; the ability to change the brightness of colors depending on the electrolyte concentration, change the smoothness of the gradient depending on the exposure time of each color, and avoid unwanted defects (stripes, blackening, color inconsistency).

Disclosure of the Invention

In this invention, the following meanings are given to the terms used:

Immersion method is an anodizing method that involves immersing a product attached to an anode into a bath with an electrolyte and a cathode, followed by anodization, while the cathode and anode in the bath should not be in contact;

The method of smooth removal with a simultaneous increase in the voltage value is a type of submersible method in which the product is also attached to the anode, but during the anodizing process it is smoothly removed with a parallel increase in the voltage value;

Color transition - a change of colors in a gradient depending on an increase in voltage (Table 1);

Preliminary oxide film - a film obtained on the entire surface of the product during anodization at U _initial ;

(U _start ) is the lowest voltage used to create a gradient at the initial anodizing stage;

(U _final ) - the highest voltage used to create a gradient at the final stage of anodization;

Defective range of values - the range of gradient voltages at which color skipping, grayness or other defect is observed;

(U _def1 ) - the lowest voltage at which a defective area in the gradient is observed;

(U _def2 ) - the highest voltage at which a defective area in the gradient is observed;

(k) - coefficient used to calculate the skip area (defect) for gradients with color transitions more than two times (k=[1;1,3]).

The objective of the present invention is to develop a method for applying gradient oxide films by anodizing to the entire surface of a product made of alloys of tantalum, titanium, zirconium, niobium, hafnium, tungsten or part thereof at different voltage values with high surface quality, a smooth transition of gradient colors and the ability to create gradients as with or without color skipping.

The technical result achieved by the claimed invention is to obtain gradient interference films, both with and without color transmission, characterized by high quality porous oxide due to the elimination of defects caused by uneven distribution of current density (j), too high or low its value, overheating of the anode and electrolyte (with an increase in voltage value), sharp immersion of the anode into the electrolyte.

The problem is solved by: using the immersion method, namely, the method of smooth removal with a simultaneous increase in the voltage value. This method allows you to obtain a gradient film both without color skipping and with color skipping, depending on the application mode. For gradients with color transitions more than two times, the coefficient k is defined, which allows you to calculate the area that gives a color skip or defect. It is this method that makes it possible to create a film that is uniform and geometrically correct in terms of the structure of the porous oxide due to a pre-created film, which is formed at the initial stage when the product is completely immersed and the initial voltage ( _Uinit ).

The film, obtained by the method of smooth removal with a simultaneous increase in the voltage value, does not produce defects during application when changing colors less than twice (inclusive). With a large number of transitions, there is a high probability of defects or color skipping. The range of stress values that produce a defect (U _def1 -U _def2 ) can be calculated using the coefficient k (k=[1;1.3]) using the formula U _def1.2 =(U _final - U _initial )/k. This defective area occurs due to repeated sequential anodization and is adjusted (leaving a color gap or maintaining a complete color transition) by changing the current density value and the removal method.

I. For gradients with less than two (inclusive) transitions, application by the smooth withdrawal method with a parallel increase in voltage involves the following operations:

1. The product must be degreased.

2. If necessary (coating part of the surface of the product), apply a dielectric to areas not involved in anodizing in order to protect the surface from being covered with an oxide film.

3. Apply the gradient film using the immersion method, first at the lowest voltage (U _start ) (at this stage a preliminary oxide film is formed), and then gradually increase the anodizing voltage to the highest (U _end ) (each color is anodized until the current density drops to 0. 2-0.3 A/dm ² ), while increasing the voltage and removing the product from the electrolyte in parallel. In this case, the current density should be selected according to graph 1 (figure 1), relative to the final voltage (U _final ).

4. If necessary (coating part of the surface of the product), remove the previously applied dielectric.

II. For gradients with more than two transitions, application by a smooth withdrawal method with a parallel increase in voltage involves the following operations:

1-2. - similar to steps 1-2 for creating a gradient with less than two (inclusive) color transitions.

3. Using the formula U _def1,2 =(U _final - U _initial )/k, determine the defective area, where k=[1;1,3].

4. - similar to step 3 in creating a gradient with less than two (inclusive) color transitions, but when reaching U _def1 and up to U _def2 , use the current density according to schedule 2 (figure 2) (current density is selected relative to U _def2 ) and the shutter speed of the created produce colors until the current density drops to 0.1 A/dm ² , after U _def2 use the same parameters of current density and shutter speed.

5. - similar to step 4 in creating a gradient with less than two (inclusive) color transitions.

III. A gradient with skipping color can only occur when more than two colors are transitioning. Defective areas in this case allow for color loss. For each of the colors, U _start , U _end , U _def1 , U _def2 were calculated so that a specific color was skipped (Table 2):

Table 2 - Calculation of gradients with color skipping

Voltage range of the created gradient, V Presumable resultant color skipping Calculated coefficient k, V 7-20 violet [13;18] 16-40 blue [24;32] 24-64 blue [40;53] 40-90 Yellow [50;66] 50-110 Orange [60;80] 60-125 Crimson [65;87]

This table includes colors from violet, since this is the first color that can be skipped, to crimson, since this is the last color that can be skipped in the color range (to create a skip of green color, a voltage is required, which does not give during interference colors).

For gradients with color skipping, application using the smooth withdrawal method with a parallel increase in voltage involves the following operations:

1-2. - similar to steps 1-2 for creating a gradient with less than two (inclusive) color transitions.

3. - similar to point 3 in creating a gradient with less than two (inclusive) color transitions, but when reaching U _def1 and up to U _def2 , hold the created color until the current density drops to 0.1 A/dm ² and change the level of immersion of the product into the electrolyte, after U _def2 use the same holding parameters and continue to gradually remove the product from the electrolyte.

4. - similar to step 4 in creating a gradient with less than two (inclusive) color transitions.

This method is well suited for creating gradients at voltages above 51 V, since in this range and with this method the colors are bright, the transitions are smooth and without defects. When creating a gradient at voltages less than 51V, the colors sometimes appear gray or mismatched.

Claims (8)

1. A method for producing a decorative colored gradient coating on the full surface of a product made of alloys of titanium, tantalum, zirconium, niobium, hafnium, tungsten or part thereof with the possibility of color transmission, characterized in that to obtain a colored gradient coating with more than two color transitions for each of the created color, the voltage region of the created gradient U _start , U _end is determined and the voltages of the defective region of the gradient - the color skip area U _def1 , U _def2 are calculated using the formula U _def1,2 = (U _end - U _start )/k, where U _start - the lowest voltage used to create a gradient at the initial anodizing stage, U _final - the highest voltage used to create a gradient at the final stage of anodization, U _def1 is the lowest voltage at which a defective area in the gradient is observed, U _def2 - the highest voltage at which a defective area in the gradient is observed, k – coefficient used to calculate the area of omission - defect for gradients with color transitions more than two times k=1;1.3, then the product is degreased, a preliminary oxide film is formed, created by anodization at the initial stage of gradient formation at voltage U _init , and a decorative colored gradient coating is obtained by anodization, which is carried out by smoothly removing the product from the electrolyte with a simultaneous increase in the voltage value, and when U _def1 and up to U _def2, the created color is held until the current density drops to 0.1 A/dm ² and the level of immersion of the product in the electrolyte is changed, and after U _def2 is reached, the same exposure parameters are used and the product is continued to be gradually removed from the electrolyte. 2. The method according to claim 1, in which a dielectric is used to coat part of the product, which is applied to untreated areas before anodizing, and after anodizing the dielectric is removed.