DIY HARDCOAT ANODIZING CHEMICALS KIT

Transcription

1 DIY HARDCOAT ANODIZING CHEMICALS KIT We provide different anodizing kits for hobbyists of their small scale anodizing line. All our dyes and chemicals in the kits are environmentally friendly products. Thus, they can be transported safely by air shipment worldwide. The Operation Sequences There are six basic steps in the anodizing process as illustrated in the above diagram. Depending on the types of alloy, some steps may not be necessary. If a matte finish is required, the etch process can produce a matte finish on the anodized parts. The longer the treatment time, the deeper etch surface obtained. Instead, a chemical or electro-polishing process can be used to brighten up the parts prior to anodizing. General process flow 1. Immerse the parts into the non-etch cleaner solution at C for 3-5 min, rinse 2. Etch the parts, if necessary at around 50 C in g/l sodium hydroxide (caustic) solution for one minute or longer to achieve a matte finish. rinse 3. If previously etched, desmut the parts at room temp for 1 minute in a 10 % nitric acid solution. rinse 4. Anodize the parts at A/dm 2 for minutes duration at room temp (20-22 C), rinse twice. The parts should stay in the rinse around 1 minutes or longer 5. Dip the parts in room temperature to 60 o C dye solution for 15 seconds to 15 min (depending on shade desired), rinse 6. Seal the parts at C nickel acetate sealant for at least 20 min, rinse Cleaning It is important to clean the parts thoroughly prior to all subsequent finishing operations. The cleanliness of the parts can be checked by a 1

2 water break test (See following section). After cleaning, do not touch the parts with bare hands as swear, dirt and oil sticks on the parts making it to be cleaned again. Anodizing The anodizing process involves placing aluminum parts into an electrolyte solution, a weak sulfuric acid, passing a low direct current through it. The aluminum parts are connected to the positive (anode) side and the negative side is connected to the negative cathode side. The cathode can be made of lead, aluminum or graphite, usually aluminum. By passing a direct current onto the anode, the aluminum surface is being oxidized to form aluminum oxide. The oxide layer looks like a honeycomb structure having many microscopic pores formed from the aluminum surface. These pores have tube-like structures and therefore accepting dyes to be adsorbed into them. Coloring & Mixing All of our aluminum dyes are water soluble and in power form. There are many ways to apply the colors onto a fresh anodized surface. The most convenient way is to immerse the part into the dye solution for a period of time. There are also other dyeing techniques which include spraying, brushing, silk screen and etc. Mixing of different dyes (Pre-mix) to form a full spectrum of colors is possible, e.g., blue plus yellow forms a green color. The parts can also be over-dye (dye into two separate color tank) to achieve the same result. It is advisable to dye at room temperature, if premix or over-dye method is used. Sealing Hot nickel acetate type sealant should be used to close the pores of the anodic coating for dyed parts. The advantage of using hot sealing method is to minimize the bleeding of the color during the sealing process. Cold nickel fluoride type sealant should be used to close the pores of natural color anodic coating. The cold sealing process works at room temperature (around 25 C) and thus, can save up a lot of energy cost 2

3 EQUIPMENTS Tanks & Anodes Polypropylene tanks in rectangle or circular size can be used for the anodizing line. Tank bars should be made of copper. Good contacts between all connections are necessary in anodizing to ensure a uniform grow of the anodic coating on the anode. The cathodes can be made of lead or aluminum. Air agitation An oil-free air pump is necessary to ensure a good circulation of the electrolyte inside the anodizing bath. Bath heating & Insulation A ceramic type of heater is a good source for heating up a hot sealant solution. Do not leave the heater in the sealing tank unattended as the solution boils away the tank will ignite. It may be advisable to use insulation material to minimize the heat loss of the hot sealant solution. Power supply A small rectifier is an ideal power source. Depending on the surface area being anodized, a 12 V rectifier delivers a current range of A should usually be enough for a small scale anodizing line. A current density of 1 A / dm 2 can be used to size the rectifier for the anodizing line. Racking Wiring system can either be made of titanium or aluminum. If aluminum is being used, it must be strip each time because aluminum is also being anodized, so, titanium is frequently used. For small parts, aluminum or titanium wires can be used for racking. For larger parts, a titanium racking system must be used. TROUBLE SHOOTING Anodizing & Coloring Fault Problem Cost Remedy Decrease in depth Color depth change in same batch Bath contamination Dye use up Inconsistence in film thickness Improve rinsing Add dye & extend dye time Replace bath 3

4 Depth differences Dark edges Patchy spots Dark dye spots Dull / Chalky surface (remove by wiping) Surface pitting & soft coating Irregular anodizing conditions Different alloys Irregular current leading to heavy buildup of the film Electrolyte carry over to dye bath Oily Local overheat by mechanical polishing Gas bubbles on anodize pores Un-dissolved dye particles Inadequate film thickness / too soft Parts too close to the cathode Keep anodizing conditions constant Dye only same alloy Reduce current density Improve rinsing Strip and re-anodize Boil up & agitate dye bath Clarify dye bath by filtration Reduce anodize temp/acid conc./time Increase tank size or place the parts further away General Faults & Reasons Questions What dyes was used? Dye bath concentration? ph and temperature? Anodic coating thickness Immersion time? Type of Sealant? Concentration? ph and temperature? Parts cleanliness? Etch and Main Reasons Wrong type of dyes used Dye time too short Anodic coating too thin Wrong sealant type Poor sealing Avoid direct sunlight and strong heat source 4

5 desmut? Parts expose to sunlight and heat? 99% of the time, cause by poor rinsing, poor sealing or anodic coating too thin NOTES Safety equipments Personal safety equipments such as goggle, hand glove as well as laboratory gown must be used all the time for operation in the anodizing line. When handling acids, a face mask to protect the breathing system is strongly advisable. Bath make-up For all make-up baths wit the exception of dyebaths, fill tanks 2/3 full of water. Add the required amount of products slowly with mild agitation. Add water to the operate level and mix again. NEVER add water into acid as this will cause excess heat generation and spattering to cause serious injuries. For the make-up of dyebaths, fill tanks with 1/3 of water and raises to the dyeing temperature. Add the measured amount of dyes into the water with stirring for at least 10 minutes. Add water to the final volume and continuous stirring until the dye solution is fully homogenized. Check the ph of the solution and adjust to the correct ph, if necessary. Water quality Whenever possible, de-ionized water should be used for all bath make-ups and rinsing operations. If de-ionized water is not available, clear tap water with low hardness can also be used for the make-ups with care. Special attention should be taken to see that the water should be free from chlorides, phosphates, silicates and iron. Hard waters and inferior water quality do cause a lot of problems in a metal finishing operation. These may include inhibitions of dye uptake from a fresh anodic coating, heavy bleeding in the sealant solution, bath turbidity, corrosion pits due to the presence of sterilized chloride ions, etc. Rinsing & Water break test The rinse following each operation is an important step in each finishing sequence. If not rinse thoroughly, acid residues clinging on the dyed parts are liable to cause spotty dyeings. They also contaminate the dye bath which leads to inactivate the dye bath and may result in break down of the dye structure. De-ionized water should be used for make-ups and rinsing after each bath operation. The parts should stay in each rinsing bath for at least 2 minutes to ensure for adequate cleaning of the parts. 5

6 The water break test is probably one of the most important steps in any metal surface operation. To pass the test, water should be sheet off the part rather than beads off when withdrawing from the rinsing bath. Water beads off means oil residues remains on the metal surface. ph control A ph meter is needed to check the ph values of the working solution. It is better to use those ph meters that can self regulated with temperature variation. Acetic acid should be added to lower the ph of the dye solution. Sodium hydroxide should be added to raise the ph of the dye solution. Sodium acetate can also be used as a ph buffer of the dyebaths. The ph adjustment of hot sealant solution can be also done in the same way. Activation of anodized parts before dyeing Fresh anodized parts should be dyed without un-necessary delay. If parts become dried up, the adsorptive capacity for dyes diminishes. The parts need to be treated in 10% of diluted nitric acid in about 30 seconds to reactivate of the anodic pores. Stripping of dyed anodic coating Stripping of colors before sealing If the dyed parts are found to be off-shade prior to sealing, they can normally be stripped or lightened in depth by treatment in dilute nitric acid or sulfuric acid. These acids cause no serious damage to the anodic coating, which can be re-dyed after the treatment. However, there are some dyes that can not be stripped or lightened in this way. The anodic coating has to be stripped in order to remove the colors on the parts. Trial and error should be used to confirm the strip ability of each dye on the anodic coating. Stripping of colors after sealing If the color fault is one that cannot be corrected by stripping and re-dyeing, or is only detected after sealing, then the coating as well as the dyeing will have to be removed and reprocessed again. The easiest way to remove the anodic coating is by immersion in a 10 % caustic soda solution at 60 o C. However, the underlying base metal is also attacked in this process, which may need a new pre-treatment to regain the original surface structure. HARD ANODIZING CHEMICALS KIT comes with our most versatile aluminum non-etch cleaner, our top quality black dye - Black SL, hot sealant CK and cold sealant SE. A 25 liters anodizing solution make-up kit at USD (The package includes 2.5 liters of 11 D non-etch cleaner, 100 grams of the black SL, 2.5 kgs of hot sealant CK) 6

7 A 50 liters anodizing solution make-up kit at USD (The package includes 5.0 liters of 11 D non-etch cleaner, 100 grams of the black SL, 5.0 kgs of hot sealant CK) LARGER CUSTOM HARD ANODIZING KITS ARE AVAILABLE. PLEASE ASK THE DETAILS PRODUCT& PROCESS DETAILS Color Black SL is supplied in power form to achieve a jet-black tone at room temperature for hardcoat anodized aluminum. Black SL has a high light fastness of 8 and a high heat fastness of 5. Hot sealant CK If the hardcoat anodized aluminum is dyed black, hot sealant CK must be used to close the anodic pores at around 90 C. Cold sealant SE Although natural hardcoat aluminum is not normally sealed, in some cases, it may be an added advantage to seal with a cold sealant to provide a protection of the surface away from the environment. REPLENISHMENT PRODUCTS All chemicals and dyes can be purchased separately at the following prices 5 liters of non- etch cleaner 11D at USD All colors in 100 grams at USD grams of Black HLF at USD grams of Black SL at USD kg of Hot Sealant CK at USD kg of Cold Sealant SE at USD COLOR CARD A set consists of two color cards can be purchased at USD 50. All the colors inside the color cards can be purchased separately at the above price. Please ask for details. 7