HAVACHROME CR3 TRIVALENT BRIGHT CHROMIUM PROCESS

Transcription

1 HAVACHROME CR3 TRIVALENT BRIGHT CHROMIUM PROCESS HAVACHROME CR3 Process is a unique trivalent chromium plating process, that is used to deposit a bright chromium deposit over bright nickel deposits. IMPORTANT: READ ENTIRE TECHNICAL DATA SHEET BEFORE USING THIS PRODUCT. FEATURES / BENEFITS: *No hexavalent chromium *Outstanding coverage and throwing power *Light, hexavalent chromium-like deposit *Tolerates current interruption and high DC ripple *Improved worker safety and simplified waste treatment *Reduced rejects from chromium skip plate and ability to plate complex parts. *Excellent appearance and improved ability to match hexavalent chromium pieces *No whitewash or staining *Metallic impurities controlled by ion-exchange *Dependable operation with consistent deposit or precipitation / filtration. color. *No high current density burning *Reduced rejects and improved appearance MATERIAL REQUIRED: 1. HAVACHROME CR3 MAKE-UP SALTS are used to make up and replenish the chromium depleted by plating and drag-out. 2. HAVACHROME CR3 COMPLEXOR is used to form a stable compound with the chromium. 3. HAVACHROME CR3 WETTER provides satisfactory metal distribution and promotes a clear metal deposit. 4. HAVACHROME CR3 REPLENISHER is used for replenishment of drag-out losses. 5. HAVACHROME CR3 LCD ADDITIVE is used to improve throwing power. Haviland Products Company, 421 Ann St. NW, Grand Rapids, MI T: (800) F: (616) Page 1

2 optimum range HAVACHROME CR3 MAKE-UP SALTS 270 g/l 250 to 280 g/l HAVACHROME CR3 REPLENISHER 135 g/l 130 to 160 g/l HAVACHROME CR3 COMPLEXOR 65 ml/l 55 to 75 ml/l HAVACHROME CR3 WETTER 2 ml/l 2 to 4 ml/l HAVACHROME CR3 LCD ADDITIVE 3 ml/l Boric Acid (H 3 BO 3 )* 15 g/l 55 to 65 g/l** Note: * use only for new make up or for trouble-shooting. ** HAVACHROME CR3 MAKE-UP SALTS contains Boric acid. MAKE UP PROCEDURE: (ATTENTION: Make up takes 2 working days!) 1) Make certain that the plating tank and the anode bars very clean. Never use a lead- lined tank. New Tank lining made of plastic (PVC, PE, and PP) is recommended. 2) Install graphite anodes into the tank. Make certain no metal hook will be immersed in the solution! 3) Into a smaller separate Make up Tank equipped with a stirrer, fill approximately 60% of the tank vol. with filtered hot (65 to 70 o C) city or treated municipal potable water. 4) Turn on the stirrer. 5) SLOWLY add the HAVACHROME CR3 REPLENISHER and stir until fully dissolved. 6) When fully dissolved, pump solution into the clean plating tank. Repeat if necessary until the entire make up amount of HAVACHROME CR3 REPLENISHER has been completely dissolved 7) Turn on air agitation in the plating tank. 8) If necessary, fill tank approximately 60% full with hot water 9) Add 15 g/l Boric acid to the plating tank and mix well until fully dissolved. 10) Add slowly and uniformly across the solution surface the HAVACHROME CR3 MAKE-UP SALTS. Make certain not to add too fast as the salt will dissolve very slowly once it settles on the tank bottom. Due to the endothermic reaction, the temperature of the solution will drop. 11) Heat the solution if temperature drops below 60 o C and air agitate until all of the HAVACHROME MAKE-UP SALTS have been added. 12) Fill plating tank with cold city water to approximately 85% of working volume. After all salts are dissolved completely, allow temperature to drop to 45 o C. 13) Add slowly and uniformly along the solution surface the required amount of HAVACHROME CR3 COMPLEXOR. Adjust solution level to operating volume with water. Maintain temperature while stirring overnight (minimum 12 hours!!) IT IS VERY IMPORTANT TO ALLOW FOR THIS REACTION TIME. IF REACTION TIME IS <12 HOURS, PROCESS PERFORMANCE WILL BE SEVERELY COMPROMISED!! 14) On the next day, while agitating the solution, add the HAVACHROME CR3 WETTING AGENT and mix for at least 30 min. 15) Next add HAVACHROME LCD ADDITIVE and mix well for at approximately 30 minutes. Adjust the solution to operating volume with water. 16) Dummy plate freshly nickel plated corrugated dummy panels (approx 50 dm 2 for every 1000 liters tank volume) for approximately 1 to 2 hours at a current density of 10 A/dm 2. 17) Measure the ph and adjust if necessary. 18) Solution is ready for start up. Haviland Products Company, 421 Ann St. NW, Grand Rapids, MI T: (800) F: (616) Page 2

3 OPERATING CONDITIONS: Agitation Filtration Moderate, uniform air agitation mechanical also possible Continuous; 2 to 4 tank turnovers per hour 5 to 10 micrometer mesh filter media. Specific gravity 1.20 ( ) Cathodic current density 8 to 11 A/dm 2 ph 2.6 optimum (2.4 to 2.8) Temperature 30 o C optimum (27 o C to 38 o C) Anodes Graphite anodes: Anode Cathode ratio: : 1 Plating speed Tank ventilation Trivalent Chrome content ( Cr +3 ) Total Boric Acid content (H 3 BO 3 ) Approx. 0.2 micron per minute at 10 A/dm2 necessary 18.5g/l (18 to 22 g/l) 62 g/l (60 to 65 g/l) GENERAL GUIDELINES: All components should be maintained within the ranges specified under "Bath Composition." Additions of all constituents should be made no less than every 5 amp-hours/litre during each eight hours of accumulated operation. Extension of the foregoing current-time relationships will result in a chemical imbalance of the solution, and the necessity to make large additions. Large additions will require additional electrolyzing to restore the bath to operating condition. Addition schedules should be established for each installation to adjust for varying amounts of drag-out. All additions should be made during, or just preceding electrolysis. The chrome solution is maintained by addition of HAVACHROME CR3 MAKE-UP SALTS, HAVACHROME REPLENISHER, HAVACHROME CR3 COMPLEXOR, HAVACHROME WETTING AGENT, and control of ph, as described below. The information given should allow for near optimum performance for most installations. Occasionally, the solution should be analyzed and adjustments made to optimize the solution. Note that large additions of HAVACHROME CR3 MAKE-UP SALTS (10 g/litre or greater), HAVACHROME CR3 REPLENISHER. (5 g/litre or greater), or smaller quantities if both are added together, may unbalance the chromium complex. This would require re-electrolysis for minutes to avoid plating defects. To avoid re-electrolysis, these additions should be separated and spread over twenty-four operating hours, along with the regular maintenance additions. Haviland Products Company, 421 Ann St. NW, Grand Rapids, MI T: (800) F: (616) Page 3

4 HAVACHROME MAKE-UP SALTS: HAVACHROME MAKE-UP SALTS are used for makeup and replenishment. They provide conductivity to the bath and also replenish drag-out. HAVACHROME MAKE-UP SALTS may dissolve with difficulty unless special precautions are used. Fast addition rates may result in the formation of wet lumps of HAVACHROME MAKE-UP SALTS which may not dissolve. The HAVACHROME MAKE-UP SALTS are, preferably distributed slowly and evenly over the surface of the solution, giving most of the material times to dissolve before further additions are made. Small, frequent additions are therefore, preferred. The concentration of HAVACHROME MAKE-UP SALTS should be maintained by keeping the specific gravity of the solution at a minimum value of An addition of 20 g/litre of HAVACHROME MAKE-UP SALTS will raise the specific gravity approximately 0.01 units. It is preferred to make this addition immediately after additions of HAVACHROME REPLENISHER. High concentrations of HAVACHROME MAKE-UP SALTS may result in the formation of some crystals, especially if the solution temperature is low. The presence of crystals may result in plugged air agitation lines or coated anodes. The latter may result in reduced current. If the crystals pose a problem, the affected equipment and anodes should be removed and cleaned (scrubbed). Low concentrations of HAVACHROME MAKE-UP SALTS will reduce conductivity of the bath, resulting in reduced current or the need of increased voltage to maintain cathode current density. HAVACHROME CR3 REPLENISHER: HAVACHROME CR3 REPLENISHER is used to replenish the chromium plated from the solution and to compensate for drag-out. It is added on the basis of ampere-hours. HAVACHROME CR3 REPLENISHER must be dissolved slowly in a bucket or in a separate small tank, using plating electrolyte as solvent and added evenly over the surface of the solution to obtain homogeneity. HAVACHROME CR3 REPLENISHER should be added at the rate of 570 g/1,000 ampere hours and after at least every eight hours of accumulated actual plating time. The addition of 1g/l HAVACHROME CR3 REPLENISHER will increase the Trivalent chrome content by approx. 0.1g/l. HAVACHROME CR3 COMPLEXOR: HAVACHROME CR3 COMPLEXOR forms a stable compound with the chromium, allowing it to plate out from the trivalent state. High concentrations of HAVACHROME CR3 COMPLEXOR may result in some precipitation of chromium salts, especially if the solution is unbalanced in other respects, such as high ph, and high temperature. Low HAVACHROME CR3 COMPLEXOR reduces plating rate. It is, therefore, important that HAVACHROME CR3 COMPLEXOR be maintained within the range specified. HAVACHROME CR3 COMPLEXOR is consumed by drag-out and electrolysis. It should be added at the rate of 1.9 litres/1,000 ampere hours until a specific consumption rate for the individual installation has been established based on solution analysis. HAVACHROME CR3 WETTING AGENT: HAVACHROME CR3 WETTING AGENT functions to clear the deposit of dark smudges and provides satisfactory metal distribution. Low HAVACHROME CR# WETTING AGENT may result in dark smudges in the deposit and decreased chromium thickness in mid-current density areas. High concentrations are not especially harmful. However, amounts greater than 10 ml/litre may result in Haviland Products Company, 421 Ann St. NW, Grand Rapids, MI T: (800) F: (616) Page 4

5 reduced coverage and/or hazy, white patches in the deposit. HAVACHROME CR3 WETTING AGENT is consumed mainly by electrolysis and should be added based on an average consumption of ml/1,000 ampere hours. LCD T-CHROME LCD ADDITIVE: HAVACHROME LCD ADDITIVE is used at the time of solution make-up to help improve throwing power. Further additions may be required in some installations, but only should be added after tests in a small pilot line. SELECTIVE ION EXCHANGE RESIN: The SELECTIVE ION EXCHANGE RESIN is used to remove metallic impurities. Please refer to the chapter metallic contamination further below. ph Optimum operating ph is 2.6. Values between can be used, however at high ph (eg.2.8), coverage is improved at the expense of plating speed. The ph should be measured with a ph meter fitted with a sleeve-type calomel electrode. Due to the dark color of the solution, most ph papers will produce unsatisfactory results and their use is not recommended. ph adjustments should be made on the basis of 2 ml/litre concentrated hydrochloric acid to lower the ph 0.1 units or 2 ml./litre of concentrated ammonium hydroxide solution (Sp.Gr. 0.89) to raise the ph 0.1 units. Additions of hydrochloric acid or ammonia water will initially produce large, temporary changes in ph, which will reach equilibrium over a period of time. Because of this, ph cannot be accurately measured for about 8-12 hours following an addition of acid or ammonia. ph adjustments should be limited to 0.2 ph units at one time. ph adjustments greater than 0.2 ph units are preferably made in steps over a period of several hours; e.g., a desired adjustment of 0.4 ph unit should be made by addition of enough hydrochloric acid (or ammonia water) to change 0.2 ph unit, waiting several hours and then adding the additional requirement. TEMPERATURE Because the process operates at temperatures C, some heating and cooling is necessary. The use of titanium coils (controlled by thermostat) is appropriate. If external cooling is used, the temperature of the circulating plating solution should not be less than 24 C, since crystallization may happen. Heating the plating solution to above 43 C will re-dissolve the crystals. Operation at high temperatures over 38 C will reduce covering power. Anodes Existing lead anodes as used for hexavalent chromium plating must be replaced by graphite anodes fitted with titanium anode hangers specially designed to ensure sound electrical and mechanical contact. As a general guide, the total immersed anode area should be twice the cathode area and should be sufficient to allow for a maximum anode current density of of 5.0 A/sq.dm. A nominal (600 mm x 50 mm) diameter anode has a maximum effective area of 10 dm 2. The top of the anode should be at least 5 cm below solution level. Copper anode bus bars should be heavily nickelchromium plated to avoid possible copper contamination, and exposed bus bar should be shielded from solution by coating with plastisol or by wrapping with plastic waterproof tape, etc. Anodes should not be removed until at least 30 minutes after plating stops as they may be saturated with Haviland Products Company, 421 Ann St. NW, Grand Rapids, MI T: (800) F: (616) Page 5

6 electrolytically produced noxious compounds. Continuous use of extremely high anode current densities will significantly shorten anode life. Anodes should be inspected for a coating or crystals if bath crystallization is noted. Operation of the bath with coated anodes will produce high anode current densities. AIR AGITATION Air Agitation helps assure uniformity of metal distribution rather than prevent high current density burning. The agitation should be mild and as uniform as possible. AMPERE-HOUR METER An ampere-hour meter is mandatory for optimum control of solution composition, as maintenance additions are best made on an ampere-hour basis. In most automatic operations, the chromium ampere hours can be related to the nickel ampere hour meter by suitable corrections for time and current. Nominal Consumption HAVACHROME CR3 ADDITIVES per 1000AH: HAVACHROME CR3 MAKE-UP SALTS: max. 100g. addition according to specific gravity HAVACHROME CR3 REPLENISHER: 570 g HAVACHROME CR3 COMPLEXOR: 1200 g (approx. 1.0 Litre) HAVACHROME CR3 WETTING A.: 40 g RECTIFIERS Existing 6-9 volt rectifiers are suitable for some installations, depending on anode area, cathode area, anode-to-cathode spacing, voltage losses in bus bars, etc. But for parts consistently requiring very good coverage, 9 to 12 volt rectifiers give more flexibility. VENTILATION Although there is no toxic chromic acid spray emitted by the Trivalent Chrome plating solution, the gassing at the cathode may, under certain conditions, produce an overspray that could be objectionable. For this reason, exhaust ventilation is recommended. Existing ventilation used for hexavalent chromium baths is satisfactory for use with this process. FILTRATION Plating solutions requiring Purifier additions may create enough insoluble material in the solution to produce a white film on the work. Filtration of the solution, especially during the period immediately following Purifier addition, may therefore be desirable. CATHODE CURRENT DENSITY/PLATING RATE It is suggested that an average cathode current density of A/dm 2 ) be used to provide a balance between consumption of the HAVACHROME ADDITIVES, deposition rate, rectifier requirements and cooling capacity. Increasing current density will result in decreasing cathode efficiency resulting in increased covering power, but at the same time decreasing deposition rate (especially in high current density areas), increasing consumption of HAVACHROME CR3 ADDITIVES, and possibly over-heating (requiring additional cooling.) In extreme cases where the Haviland Products Company, 421 Ann St. NW, Grand Rapids, MI T: (800) F: (616) Page 6

7 maximum coverage is required as well as uniformity of metal thickness, it may be advantageous to plate at higher current density: e.g A/dm 2. Under optimum conditions, 0.2 to 0.25 micrometers of chromium will be deposited per minute at 10 A/dm. Increasing current density will not significantly increase the plating rate due to a decrease in cathode efficiency. METALLIC CONTAMINATION Due to the very mild acidity of the solution (ph ) and the continuous removal of trace metallic contamination by plating, there should be no excessive build-up of impurities unless parts are frequently lost from racks or if post-nickel rinsing is inadequate. In some cases, electrolytic purification may be recommended to ensure that trace elements are kept within the tolerable levels, and this is best achieved by plating periodically for a few hours at ( A/dm 2.) using nickel plated corrugated steel cathodes. The information below gives a guide to maximum levels of trace elements when present alone and shows that copper and zinc must be maintained at a low level. In practice, multiple metallic contaminations may compound the problem. For example, 50 ppm (0.05 g/litre) zinc, 100 ppm (0.10 g/litre) iron and 10 ppm (0.01 g/litre) copper may be more harmful than 200 ppm (0.20 g/litre) nickel alone, even though all elements are present within their tolerance limits. Analysis for foreign metals is done by AA. Removal of metal impurities with Purifier Purifier is used to remove copper, zinc, nickel and iron, together with many less common metals, from Trivalent Chrome Plating Solutions by precipitation. Additions of Purifier shall NOT be made to plating solutions while in operation. Oxidizing conditions during operation of plating solutions will permanently damage the solution by reacting with Purifier and producing by-products that affect the chromium coverage and color. To ensure that the plating solution is free of oxidizing agents, stop plating for 24 hours and then add the needed volume of diluted Purifier (Dilute 1: 5 with water and is best if dosed in small portions, and under strong air agitation to make sure a very good distribution of Purifier in the plating bath) Do not add more than 2 ml/l Purifier for one treatment. Normally the treatment will create a fine precipitation and the plating bath must be well filtered. It also will consume HAVACHROME CR3 COMPLEXOR. After the treatment, add up to 1 ml/l HAVACHROME CR3 COMPLEXOR into the bath. Note that lack of HAVACHROME CR3 COMPLEXOR results in yellowish and greyish LCD and /or poor coverage. Hull cell tests are recommended to correct this. Removal of impurities with Ion exchanger Resin (preferred method). HAVACHROME CR3 RESIN is a selective ion-exchange resin used in the purification of Trivalent Chrome Plating Process. HAVACHROME CR3 RESIN has preferential adsorption for certain metal ions making this resin the obvious choice for the removal of metallic impurities. The order of preference for these metallic impurities is Cu +2 > Ni +2 > Zn +2 > Fe +2. The resin will adsorb these ions and hold them until it reaches its holding capacity of approximately 50 grams of metals per liter of resin. If the Trivalent Chrome plating solution contains no impurities, then the resin will complex with the Cr +3 ions and release them when the other impurities that are dissolved in the bath pass through the column. Once the resin reaches its holding capacity limit, regeneration is required. This involves exchanging the metal ions with sulfuric acid and/or ammonium hydroxide solutions. REGENERATION Haviland Products Company, 421 Ann St. NW, Grand Rapids, MI T: (800) F: (616) Page 7

8 Before using the HAVACHROME CR3 RESIN for the first time, it must be conditioned with dilute sulfuric acid solution. The Trivalent Chrome plating bath should also be filtered before passing it through the RESIN to prevent the plugging of the resin bed with suspended particles or salts. The following procedure describes only the regeneration of HAVACHROME CR3 RESIN. No mention is made of the equipment involved or how to use the equipment for regeneration. It is the user s responsibility to follow the proper procedures provided by the equipment supplier. Regeneration Procedure 1. Make sure the regeneration unit is turned off. 2. Drain the excess Trivalent Chrome plating solution from the RESIN reservoir, hose and back to the plating tank. 3. Flush the RESIN with 5 to 10 bed volumes of water to remove the residual plating solution left on the resin. This should yield a clear effluent. 4. Drain off the water from the resin bed. 5. Pump the regeneration solution (i.e., either sulfuric acid or ammonium hydroxide) through the RESIN bed at a flow rate of 1-2 liters per minute for a period of 10 resin beds or until all of the metal ions have been exchanged from the RESIN, as determined by analysis. 6. Flush the RESIN bed, hose and pump with water to remove the regenerating solution left behind in the unit to a ph of The RESIN has now been regenerated and is ready for use. Solution passed through it and it can now be returned to the plating tank. 8. If an ammonium hydroxide cycle has been run, it is suggested that the column be rinsed and then sulfuric acid be passed through the column. This will totally rejuvenate the column and adjust the column ph so as to not "shock" the plating solution. Regenerating Solutions Approximately 1 Normal ammonium hydroxide and 2 Normal sulfuric acid solutions are recommended. Suggested dilutions are: Ammonium Hydroxide (NH 4 OH): Add 130 ml of NH 4 OH (30%) to 870 ml of water for each liter desired. 2 Normal Sulfuric Acid (H 2 SO 4 ): CAUTION: ALWAYS ADD ACID TO WATER. While mixing, carefully add 53 ml of H 2 SO 4 (100%) to 947 ml of water for each liter desired. Haviland Products Company, 421 Ann St. NW, Grand Rapids, MI T: (800) F: (616) Page 8

9 Calculation of Bed Volume (BV) To calculate the resin bed volume (BV) of a cylinder, use the following formula: BV = *(pi) x (radius of cylinder) 2 x (cylinder height) Example: Resin bed dimensions: Height = cm Radius = 5.08 cm *(pi) = 3.14 BV = *(3.14) x (5.08 cm) 2 x (30.48 cm) = 2470 cm 3 = 2.47 liters Regeneration Frequency The regeneration frequency will depend on the build-up of contaminants from drag-in or parts falling off the racks into the Trivalent Chrome plating bath. The best way to determine this frequency is to analyze the plating solution before start-up and at the end of the day or a few days to determine the build-up of contaminants. This information will help establish a regeneration schedule. Once the schedule is set, only infrequent analysis is needed to confirm the contamination build-up in the plating bath. Regenerating more often than necessary will remove the bath constituents as well as contaminants and is not recommended. The following tables are given as guidelines for the initial regeneration frequencies. 2N Sulfuric Acid: Nickel & Zinc Conc. (mg/l) Time Between Regeneration (Hours) N Ammonium Hydroxide: Copper Conc. (mg/l) Time Between Regeneration (Hours) Haviland Products Company, 421 Ann St. NW, Grand Rapids, MI T: (800) F: (616) Page 9

10 Regeneration with ammonium hydroxide is not necessary unless there has been copper contamination in the plating bath. Regeneration with ammonium hydroxide will produce a bluish, purple color as it complexes the copper ions. Sulfuric acid will not remove copper from the resin. If the resin is loaded with copper and not regenerated with ammonium hydroxide, it will not remove nickel or zinc. If copper contamination is not a problem, then ammonium hydroxide regeneration need only to be done every 4 to 6 sulfuric acid regenerations. The above charts should be used only as guidelines and the actual regeneration frequencies for each location should be verified by analysis. SAFETY INFORMATION: HAVACHROME CR3 ADDITIVES may cause skin irritation. Use chemical goggles and rubber gloves when handling. Always read the Material Safety Data Sheets for any chemical product to ensure familiarity with the methods of safe handling and the health hazards associated with the product WASTE DISPOSAL: Wastes must be tested using methods described in 40 CFR Part 261. It is the generator s responsibility to determine if the waste meets applicable definitions of hazardous wastes. Dispose of waste material according to Local, State, Federal, and Provincial Environmental Regulations. When empty, containers may still be hazardous because of product residue. All labeled hazard precautions must be observed. Consult MSDS for additional safety and waste treatment information. NON-WARRANTY: The data contained in this bulletin is believed by Haviland Products Company to be true, accurate and complete. However, since final methods of use for this product are in the hands of the customer and beyond our control, we cannot guarantee that the customer will obtain the results described in this bulletin. Haviland Products Company cannot assume any responsibility for the use of this product by the customer in any process that may infringe the patent rights of third parties. Haviland Products Company, 421 Ann St. NW, Grand Rapids, MI T: (800) F: (616) Page 10