Types of anodizing defects in aluminum alloys

Fingerprint-like corrosion

1. During sawing and loading the basket in the extrusion process, the gloves used by workers become dirty, leaving stains after contact with the profile surface. After aging, the surface stains on the profile cannot be removed by oxidation;2. In the process of oxidation and upper discharge, the worker's gloves are used for a long time, especially after the oil stain adhesion, the handprint is at the end of the profile, and the handprint is in the form of localized corrosion after oxidation ;3 . After the top line, the parking time is very long without oxidation treatment;4. Incomplete degreasing before oxidation.

1. Pay attention to the cleanliness of gloves during the extrusion and upper threading process, and replace dirty and wet gloves in time;2. After oxidation, the profile should not be placed for more than 6 hours;3. Extend the degreasing time.

Scratched

Collision between materials, improper operation or collision and scratches between materials and structures, etc.

1. The upper row must be handled carefully and the material must be lifted without collision between materials;2. The edge of the material frame should be covered with a rubber protective cover;3. Each lift should not exceed 6 rows, and profiles with different lengths should be placed separately;4. Damaged buffer strips must not be used in the lower row process, and violent collisions are not allowed.

Overlapping crossing

1. The connection gap is too dense, resulting in abnormal contact;2. The binding and drainage strength is not sufficient. During the washing process, the aluminum wire or fixing loosens, resulting in the profile sliding on the row rod, resulting in the bonding between the materials, which is caused by alkaline corrosion, acid corrosion, oxidation and electrophoresis treatment.

1. Adopt the correct binding and arrangement method, tie three aluminum wires with electrophoretic materials (two small materials), and keep a distance of 2-3 fingers between the upper and lower profiles;2. The profile with large drop strip in the middle should be tied to the center line according to the order requirements;3. The slope of the lower groove increases and the exhaustion process of the electrophoresis groove must be slow to avoid adhesion between the profiles caused by violent shaking.

In severe cases, dimensional accuracy is affected due to dissolution of profiles.

Rough engraving

1. The temperature of the alkaline tank is too high;2. The alkaline concentration is very high;3. The concentration of aluminum ions in the alkaline tank is very low;4. The alkaline corrosion time is very long;5. The alkaline liquid in the tank is polluted;6. There are many moments of rework.

1. Adjust the tank liquid conditions (sodium hydroxide concentration, dissolved aluminum ion content and temperature);2. Adjust the processing time;3. Regularly clean the tank slag and adjust the tank liquid;4. Reduce the number of repeated processing.

Insufficient engraving

1. The temperature of the alkaline tank is too low;2. The alkaline corrosion time is very short;3. The alkaline concentration is very low;4. The concentration of aluminum ions in the alkaline tank is very high.

1. Pay attention to controlling the temperature and concentration of the alkaline tank;2. The alkaline corrosion time must be prolonged appropriately;3. Reasonably adjust the concentration of aluminum ions.

Irregular degreasing

1. Insufficient degreasing time;2. The effective components of the degreasing liquid in the tank are insufficient;3. The oil stain on the surface of the part is serious.

1. Add degreasing agent;2. Extended immersion time ≥ 3 minutes;3. Workpieces with serious oil stains on the surface should be manually cleaned and pretreated.

Bubble（anodic oxide）

1. Inadequate elevation angle;2. Very fast channel speed;3. The shape of aluminum is not conducive to the elimination of gases;4. The anti-foam bag is damaged.

1. Controlling the inclination of the lower groove;2. Extend the pre-soaking time;3. Damaged anti-foam bags must be replaced in time.

Since the old oxide film is not removed during reworking, a new oxide film cannot be formed in this area during reoxidation, and a concave-convex removal layer will appear at this time.

Remove the net

1. Insufficient immersion time of the reworked pickling profile in the sulfuric acid immersion tank;2. Insufficient alkaline attack demoulding time.

1. Extend the immersion time of the sulfuric acid solution;2. Extend alkaline recording time.

There is a black spot in the center of the spot as the core, which spreads out and extends many claws, like an octopus in the sea.

Rinse water corrosion

1. The extruded profile contains a small amount of zinc or gallium, which reacts with Cl – or f ions in the water washing tank after the neutralization treatment process;2. After the embryonic material is neutralized, it remains in the water tank for a long time;3. The sink is polluted.

1. Monitor the aluminum bar production process and control the zinc or gallium content;2. Control the material production speed to ensure that the embryonic material does not remain soaked for a maximum of 10 minutes;3. Nitric acid concentration in the neutralization tank ≥ 5% (5% – 8%);4. Increase the drainage volume to ensure the sink is clean.

White color

1. There are inclusions in the alloy, making the oxide film discontinuous;2. The alkaline mist is adhered to the oxide film.

1. Strictly control the rod casting process;2. Arrange the oxidation of the workpiece after the top line as soon as possible;3. Improve workshop ventilation facilities.

Electric burning

1. Excessive oxidation current density;2. Short circuit occurs when aluminum is in contact with the cathode plate;3. Poor contact between aluminum and fixing;4. The current increases very quickly during anodic oxidation;5. The cathode is damaged and the area is too small; Preventive measures.

1. The oxidation current density should not be too high, and the current density should be controlled between 1.2-1.5mA/dm²;2. The distance between the posts must be well controlled when lowering the groove, and it is strictly prohibited for the profiles to touch the cathode plate;3. The top row of bars must be polished, the bent screws must be tightened, and the material head must be tightened during fixing;4. The current smooth rise time setting must meet the requirements;5. Replace the damaged cathode plate in time.

Excoriation

1. The extrusion cylinder is not centered with the extrusion rod, so that foreign bodies on the surface layer of the ingot or the inner wall of the extrusion cylinder are enveloped and appear on the surface of the extruded profile;2. Because the position of the die hole is very close to the outer circle during die design.

1. In mold design, the mold hole should be located in the center of the mold as far as possible; For hollow profiles, the circumscribed circle of the bypass hole must be reduced;2. Regularly check the alignment of the extrusion cylinder and extrusion rod and adjust them in time to leave more residual pressure;3. Remove foreign bodies on the inner wall of the extrusion cylinder and the fixed extrusion pad;4. Reduce the temperature of the extrusion pad and avoid excessive lubrication;5. Increase the temperature of the extrusion barrel and ingot.

Anodizing and coloring

1. The coloring voltage is too high or the coloring time is too long;2. The dye solution is polluted;3. The barrier film formed during oxidation is very thin or irregular.

1. Correct the staining conditions;2. Remove impurities;3. Increase the oxidation voltage.

Black dots

1. The concentration of chloride ion in the oxidizing electrolyte is too high.

1. Replace the tank liquid to ensure the stability of the oxidation tank liquid.

Pinhole

1. The hole sealing time is too long;2. The high film material is stirred without air; The heat is not exchanged in time;3. The bottom line is operated wildly, the tension on the profile is too large, and the oxide film is cracked.

1. Adjust the hole sealing time;2. Aerate and stir when the high film material is oxidized;3. Standardize bottom line operation.

Iridescence

1. In the heat seal hole, poor sealing is caused by the presence of silica and phosphate;2. In cold sealing holes, excessive sealing is caused by too high sealing tank liquid concentration, too high tank temperature, too long sealing time, etc;3. Poor anodic oxidation and electrolysis;4. The sealing film is corroded

1. Adjust the liquid composition in the tank;2. Appropriately reduce the tank liquid temperature and reduce the hole sealing time;3. Reduce the nickel ion content in the sealing groove;4. Regularly clean the liquid scum in the tank and filter the liquid in the tank frequently to keep it clean.

Pinhole (film)

1. When the aluminum material enters the electrophoresis tank, bubbles or air on the surface of the ink solution are sucked in;2. There is air entry into the circulation system;3. The cathode shielding is weak or the antifoam bag is damaged and there are fine bubbles in the ink solution;4. The electrophoresis voltage is very high and the electrolytic reaction is violent, resulting in bubbles;5. The impurities mixed in the electrophoretic paint adhere to the paint film;6. The temperature of the electrophoresis bath is too high;7. The low pH value of the electrophoresis tank solution and the excess solvent decrease the polarization ability of the paint film, resulting in the poor ability to resist impurities;8. Poor pre-treatment degreasing;9. The surface of the blank is corroded due to long storage time.

1. The bottom groove should be tilted and shaken up and down several times;2. Regularly check the operation of the equipment;3. Replace the antifoam bag;4. Reduce the electrophoresis voltage;5. Replace the filter bag regularly;6. The temperature of the electrophoresis tank must be controlled within the process range;7. Adjust the tank liquid process parameters to the normal range;8. Increase the degreasing intensity of pre-treatment, add nitric acid regularly and improve the passivation resistance9. The extruded embryo must be oxidized and electrophoresed in time.

Chromatic aberration

1. Poor conductivity;2. The clamp is not tight;3. Coloring is inaccurate.

1. Polish the water chestnut of the conductive rod until the color of the substrate is exposed;2. Secure the material well to avoid loosening;3. The colorist must check the color strictly according to the standard color chart and correct any deviation in time.

Acid drool stain

1. The acid and alkaline solution fixed on the fixture or material rack is not completely cleaned in the subsequent water washing process and flows onto the surface of the aluminum;2. There is acid-base solution on the aluminum surface that has not been cleaned;3. Once sealing is complete, the remaining materials are crossed from the drainage area.

1. Thoroughly clean the clamping bracket and material;2. The profile of the small internal cavity must be cleaned several times;3. Do not cross with other material racks;4. Ensure that the process parameters of each wash tank meet production requirements;5. When lowering the oxidation tank, wash the conductive beam with a water pipe.

Sealing obscenity

1. The calcium or magnesium ion in the seal tank is too high;2. The turbidity in the sealing groove is absorbed by the aluminum surface, which is not cleaned in the subsequent water washing process;3. The hole sealing time is too long;4. The sealing fluid is aged.

1. Ensure the dryness of the groove after washing;2. Increase seal tank liquid filtration to reduce sedimentation;3. Hold the hole sealing time;4. Set up new tank liquid.

No local movies

1. Poor conductivity;

2. The soaking time in the washing tanks with RO1 and RO2 water is too long;

3. The solvent content in the water washing tank is too high;

4. The pH value of the electrophoresis tank is too high;

5. The temperature of the hot water tank is too high and the soaking time is long, and the oxide film hole is closed.

1. Check that the line and connecting bar are tight;

2. Strictly control the water washing tank immersion time (2-3 minutes);

3. Control the solvent content according to the process requirements;

4. The pH value of the tank liquid should be detected frequently and refined in time when it is high;

5. Strictly control the hot water tank process.

Dust stain

1. The water washing tank before the electrophoretic painting process is not clean or the conductivity is too high;

2. There are coarse mechanical impurities in the electrophoresis tank solution;

3. Floating objects such as dust in the workshop air fall onto the aluminum materials placed in the drainage area;

4. There is dust and other impurities in the curing oven.

1. Replace the water in the washing tank and regularly check the water quality;

2. Strengthen the filtration frequency of the electrophoresis tank solution and replace the filter bag;

3. The electrophoresis workshop must have an independent air circulation system and be cleaned daily;

4. Regularly clean the curing oven and clean or replace the hot air circulation filter screen.

Bubble (film)

1. When the aluminum material is immersed in the electrophoresis tank, it will be enveloped in bubbles or air on the surface of the ink solution;

2. The ink solution contains small bubbles;

3. There are many bubbles on the aluminum surface and the paint liquid has poor fluidity and cannot be removed;

4. The inclination angle is not sufficient in the process of aluminum entering the groove;

5. The ink inlet valve is not closed tightly and air is inhaled;

6. The solvent A content in the tank liquid is low.

1. Increase the slope of the lower profile slot, lower the slot slowly, wait 30 seconds after lowering the slot, and conduct electrophoresis after energizing;

2. Check whether the anti-foam bag is damaged;

3. Add a certain amount of solvent B or increase circulation;

4. Always check the valve closing condition after pumping the paint liquid;

5. Add an appropriate amount of solvent A

Pwodreing(JIS)

1. The electrolyte temperature is too high;

2. The concentration of aluminum ions is too high;

3. Excessive current density;

4. Very long oxidation time;

5. Too long soaking time after oxidation;

6. Insufficient mixing of the oxidation tank liquid;

7. Local suspended materials are very dense.

1. Adjust the tank liquid temperature;

2. Often separates excess aluminum ions;

3. Use appropriate current density;

4. Grab the oxidation time;

5. Control the immersion time;

6. Fully ventilate and stir during anodizing;

7. Control the distance between the top lines.

1. The coating is too thick;

2. The curing temperature is too high or the curing time is too long;

3. The electrophoresis tank is polluted;

4. Abnormal quality of electrophoretic ink;

5. After oxidation, soak in the water tank for a long time, resulting in yellowing of the oxide film and yellowing of the product due to the transparency of the paint film;

1. Improve painting conditions and reduce coating thickness;

2. Adjust the oven temperature to the range required by the process;

3. Refining electrophoresis tank liquid;

4. Purchase electrophoretic ink with stable quality and carry out regular sampling inspection for quality stability;

5. Control the water quality and water washing time after oxidation.

1. The main electrophoresis tank and RO water washing tank have not been cleaned for a long time, and the tank wall is fixed with solidified old paint, which is scratched and fixed on the profile during production;

2. When acid is mixed in the main electrophoresis tank or RO water washing tank, part of the coating resin condenses and adheres to the profile;

3. When adding ink solution to the main electrophoresis tank, the mixing is uneven and the emulsification is not complete.

1. Regularly clean the main electrophoresis tank and washing tank with RO water to reduce old ink adhering to the tank;

2. Prevent acid from mixing in the main electrophoresis tank and RO water washing tank;

3. When adding ink solution to the electrophoresis main tank, stir for at least 30 minutes and pump into the main tank after complete emulsification.

acid drool stain (film)

1. The retention time after electrophoresis outside the tank is too long;

2. Inadequate coating concentration;

3. Insufficient washing after electrophoresis;

4. The solid content of the RO2 washing tank is too high;

5. There are acid-base water droplets in the conductive beam.

1. The electrophoresis residence time after grooving should be 1 min;

2. Control the coating concentration in strict accordance with the process requirements;

3. Properly extend the washing time after electrophoresis;

4. Reduce the solid content of the wash tank with RO2 water;

5. The oxidation process must completely spray water to wash the beam.

1. Water droplets adhere to the surface of the semi-dry paint film, resulting in changes in gloss during curing;

2. There are impurities in the water droplets attached to the surface of the paint film, which change the gloss or color;

3. The water quality of the previous washing with pure hot water is not qualified or the soaking time is short.

1. Extend the draining time;

Ensure sufficient hot water and soaking time.

Bubble (colored)

Inadequate elevation angle;

Very fast channel speed;

The shape of aluminum does not favor the elimination of gases;

The anti-foam bag is damaged.

Controlling the inclination of the lower groove;

Extending the pre-impregnation time;

Damaged anti-foam bags must be replaced in time.

Sealing failure

1. Insufficient hole sealing time;

2. The sealing temperature is low;

3. The pH value of the tank solution is not within the process range;

4. The thickness of the oxide film seriously exceeds the specified film thickness.

1. Extend the hole sealing time;

2. Adjust the sealing temperature;

3. Adjust tank liquid parameters to the process range;

4. Measure the thickness of the oxide film and determine the sealing time according to the actual film thickness.

Or seriously exceed customer requirements as shown in the figure below.

At this time, although the customer may accept it, it is not advisable to increase the oxidation cost; Oxide film thickness standard.

The thickness of the oxide film is not up to standard

1. Inaccurate calculation of oxidation time;

2. The output current of the silicon generator is inconsistent with the configuration;

3. The binding bar is loose.

1. Calculate the appropriate oxidation time in strict accordance with the standard;

2. Frequently check the actual current output value of the silicon oxide machine to facilitate production and adjust the oxidation time in time;

3. Bonding and agreement must be strengthened.

1. The water temperature of the hot water tank is low and does not meet the process requirements;

2. Curing temperature and time do not meet the lower limit of process requirements;

3. Soak in hot water for a long time and the oxide film is closed;

4. Aging of tank liquid;

5. The combination ratio of hard monomer and soft monomer in the original ink does not meet the requirements.

1. Keep the hot water tank temperature within the process range;

2. Adjust the curing oven temperature and curing time according to the process range;

3. Control the hot water tank soaking time to about 6 minutes;

4. Replace some liquid in the tank;

5. Adjust the combination ratio of hard monomer and soft monomer in the original ink.

1. The thickness of the paint film does not meet the requirements of the national standard;

2. The hot water tank and pure water tank are polluted;

3. The acid value of the liquid in the tank is high;

1. Regularly check the paint film thickness to ensure that the paint film thickness meets the requirements of the national standard;

2. Frequently replace the filter bags of the hot water tank and pure water tank, regularly detect the pH value of the tank liquid, and timely replace some tank liquid if it exceeds the process range;

3. Separate tower C several times and adjust the acid value within the normal process range.

This line is unavoidable, but it cannot exceed the length limited by the customer, otherwise it will not be qualified.

mooring line mark

1. The positioning of the conductor rod in the top line is not accurate;

2. The upper binding thread is loose, causing the profile to move up and down and shift during pre-treatment;

3. The connection angle and the bottom groove angle are insufficient.

4. The specification of the conductive rod does not meet the process requirements.

1. The distance between the conductive rods must be determined during the upper line, and the upper and lower connecting lines must be consistent.

For parts with special requirements, special conductive rods and accessories must be used;

2. Aluminum wire lashing must be used for the top row and the profile must not be left loose.

Fixing must be used in the top row to ensure that the profile does not slide up and down;

3. Tie and arrange from the bottom hole of the conductor rod to ensure that there is sufficient angular tilt at both ends. When lowering the groove, the angle must be greater than 30°;

4. The conductive rod must meet the requirements of the operation specification for conductive rod in the oxidation workshop, and those that do not meet the requirements must be replaced in time.

1. The size of the extruded materials received is not qualified;

2. The oxidation process has been reworked many times.

1. Strengthen the inspection of material received in the upper line;

2. Try to make finished products successfully in one go.