Technical Data Sheet CHEMEON TCP-HF

Transcription

1 Technical Data Sheet CHEMEON TCP-HF (formerly METALAST TCP-HF) A ROHS, WEEE, ELV and OSHA PEL compliant chromium (III) conversion coating used for immersion, brush, and spray applications. Approved for MIL-DTL-81706B and MIL-DTL-5541F Type II, Form1, Class 1A and Class 3, Methods A, B, and C. CHEMEON TCP-HF is also available in pen form see the technical data sheet for CHEMEON TCP-HF Touch-Up Pen. Introduction CHEMEON TCP-HF (formerly METALAST TCP-HF) is a trivalent chromium chemical conversion coating for aluminum alloys, magnesium, and zinc alloys, as well as a sealer for anodized aluminum. It produces a protective coating on metal, which minimizes corrosion as well as improves adhesive bonding capabilities of the surface. Features include: Hexavalent chromium-free passivation on aluminum, magnesium, zinc and zinc alloys Excellent bare metal corrosion protection on aluminum that is comparable to hexavalent chromium chemistry Produces an excellent adhesive substrate when used as a pretreatment for paint and powder coat applications, which results in extended corrosion resistance Can be used to re-coat stripped substrates, such as aircraft Can be used to touch-up products used in the field Approved for MIL-DTL-81706B and MIL-DTL-5541F Type II, Form1, Class 1A and Class 3, Methods A, B, and C Seal for anodic coatings. Sealed surfaces surpass the requirements of MIL-A Approved as an anodic sealant per Pratt and Whitney PWA B. U.S. Patent Number 6,375,726 (PCT/US 01/45434); 6,511,532 (PCT/US 02/35599); 6,521,029; and 6,527,841 (PCT/US 02/35490) GMW3059 Compliant TCP-HF contains no prohibited substances Approved as paint pretreatment on magnesium for GMW14669 for Type B2 Operating Summary Form TCP-HF is a concentrated liquid which is diluted by the customer for use in immersion, spray, and brush applications on bare aluminum, or as a post anodize seal. For bare aluminum applications, the concentration range for TCP-HF is: TCP-HF 10-50% by volume (25-30% v/v suggested) Balance DI or RO water For use as an anodic seal, the concentration range for TCP-HF is: TCP-HF 5-30% by volume (25-30% v/v suggested, adjust to avoid powdering) Balance DI or RO water SW CHEMEON Surface Technology All Rights Reserved 1

2 Recommended Operating Parameters conversion coating on bare aluminum Time: 1 to 15 minute contact time (5-6 minute recommended) Recommended Operating Parameters seal for aluminum anodize Time: 1 to 10 minute contact time (2-5 minute recommended, adjust to minimize powdering) Detailed process information is found in the Application section of this Data Sheet. Solution Makeup CHEMEON TCP-HF comes as a concentrate. The makeup is the same for conversion coating and anodic seal. The TCP-HF can be used at % by volume, 25-30% is recommended for use as a conversion coating. Bath Preparation Example 28% by volume: Note: Before initial charge, thoroughly clean the tank. For a 100-gallon bath: Fill the tank half full with deionized or RO water Add 28 gal. CHEMEON TCP-HF with continuous mixing Fill the tank to operating level Adjust the ph of the tank to (3.8 to 3.9 recommended), if necessary Filter as required to remove precipitation using a 1-20 µm polypropylene filter. ph adjustments: Solution control: Use dilute sulfuric acid to lower the ph. Use dilute sodium hydroxide or potassium hydroxide to raise ph Note: ph adjustments should be made very slowly using continuous mixing. ph should be measured regularly. Do not let ph exceed 4.0 Analyze TCP-HF by titration or spectrophotometrically. Equipment Tank material: Heater material: Water: Polypropylene, Koroseal-lined, 316 Stainless Steel, or Teflon lined tank. Teflon coated heater recommended. Deionized, distilled, or reverse osmosis SW CHEMEON Surface Technology All Rights Reserved 2

3 Application Procedure - Details Conversion coating Application on bare aluminum The application consists of the following general steps: 1. Solvent (acetone or isopropyl alcohol) wipe if needed 2. Clean 3. Rinse 4. Acid activate (unless using CHEMEON Cleaner 4000) 5. Rinse 6. Treatment with TCP-HF solution 7. Rinse 8. Dry The work is ready to continue the next manufacturing step after drying. Maximum neutral salt spray performance is achieved with a minimum 24-hour cure after dry. To achieve best results, the bare aluminum surface must be degreased and/or cleaned prior to treatment with CHEMEON TCP-HF. Excellent results have been obtained using a mild alkaline cleaner. Typically, etching cleaners do not perform as well in applications where corrosion resistance is paramount. CHEMEON Cleaner 1000 is a good choice for the application. After cleaning, the surface is activated with 50% v/v concentrated nitric acid (I.e., a 1:1 mixture of concentrated nitric acid and water) or an aluminum deoxidizer. Rinse water should be clean and clear, preferably made from DI or RO water. Dry the fresh coating gently with low pressure compressed air, or simply allow to air dry. High pressure air may damage the uncured coating layer. Note: CHEMEON Cleaner 4000 acts as both cleaner and activator. Do not follow Cleaner 4000 with an acid activation step. See the Technical Data Sheet for CHEMEON Cleaner 4000 for more information. TCP-HF Operation - Immersion Concentration: TCP-HF 10-50% by volume (25-30% v/v recommended) Immersion time: 1 to 15-minute contact time (5-6 minute recommended) Rinse and carefully dry the work after TCP-HF treatment. The ph of a CHEMEON TCP-HF bath should be carefully monitored and the tank should be agitated while making ph adjustments. During immersion, the bath should be still (not agitated) or may be lightly agitated. SW CHEMEON Surface Technology All Rights Reserved 3

4 Example immersion process: 1. Alkaline Clean - per manufacturer s directions, verify that waterbreak free surface is achieved upon rinsing 2. Rinse 1-2 minutes, ambient temperature, DI or reverse osmosis recommended 3. Acid activate 1-2 minutes, 50% v/v concentrated nitric acid or deoxidize per manufacturer s directions. Not necessary if using CHEMEON Cleaner Rinse 1-2 minutes, ambient temperature, DI or reverse osmosis recommended 5. Treatment with TCP-HF solution as above 6. Rinse ambient temperature, DI or reverse osmosis recommended 7. Dry air dry or low pressure compressed dry air Powdery surfaces after application are often the result of one or more of these conditions: Immersion (coating) time too long Bath temperature too high ph too low Lack of coating is often due to: Immersion time too short Temperature too low TCP-HF Operation Spray and Brush Concentration: TCP-HF 10-50% by volume (25-30% v/v recommended) Immersion time: 1 to 15-minute contact time (5-10 minute recommended) Expected coating weight: mg/ft 2 (20 mg/ft 2 recommended) To ensure NADCAP and customer compliance, first verify whether or not the customer specification has a required method for spray or brush application. In the absence of customer direction, a preparatory solvent wipe, soap clean, and rinse should produce acceptable results with TCP-HF. For spray and brush application, the objective is to apply the TCP-HF to the surface so that it can react and form the conversion coating. The surface must stay wet but should remain relatively undisturbed during application. Details are provided below. Cleaning: For brush and spray operations where immersion is not possible or desirable, the surface must be chemically or mechanically cleaned such that a water break free surface is obtained after rinsing. CHEMEON Cleaner 1000 SP is available for spray cleaning applications. Do not use iron containing abrasives such as steel wool or a wire brush. Activation: If the area to be sprayed cannot be activated by chemical means (deoxidizer or nitric acid) then mechanically remove the oxides. Scrub the surface of interest with wet abrasive pads. Without allowing the part to dry, rinse the part with cold running water. Clean the surface with wet wipers until all residue is removed from the part and no longer evident on a fresh wiper. Flush with water, leaving the surface wet. Rinsing: Rinse the area thoroughly after cleaning to remove chemicals and debris. A water break free surface is a good indicator that the surface is sufficiently clean to coat with CHEMEON TCP- HF. Be sure to rinse the work gently after TCP-HF application as well. SW CHEMEON Surface Technology All Rights Reserved 4

5 Drying: Dry the fresh coating gently with low pressure compressed air, or simply allow to air dry. High pressure air may damage the uncured coating layer. Application by Spray TCP-HF may be sprayed using a simple misting spray bottle, garden sprayer, etc. The purpose of the sprayer is to simply wet the surface with TCP-HF. Spray the surface, allow the TCP-HF to sit on the surface (dwell) and repeat until the desired total contact time is achieved. Good results are achieved with a total contact time of 1-15 minutes, 5-10 minutes is usually sufficient. Example: 1. Clean, activate, and rinse as described above 2. Spray TCP-HF onto the area of interest until wetted 3. Wait seconds while the liquid reacts with the surface. Do not allow the surface to dry 4. Gently re-spray and wait as above. 5. Repeat for a total of 5-10 minutes 6. Rinse gently 7. Dry Do not allow the surface to dry during application. Be sure the sprayer is oil-free. Application by Brush TCP-HF may be brushed or swabbed onto the surface. Wet the surface, allow the TCP-HF to sit on the surface (dwell) and repeat until the desired total contact time is achieved. It is important that the reapplication of TCP-HF is done gently. Do not forcefully brush the surface or the uncured coating may be disturbed and damaged. Video instruction is found at Good results are achieved with a total contact time of 1-15 minutes, 5-6 minutes is usually sufficient. Example: 1. Clean, activate, and rinse the work as described above 2. Apply TCP-HF to the area of interest until wetted 3. Wait approximately seconds while the liquid reacts with the surface. Do not allow the surface to dry 4. Re-wet and wait as above. 5. Repeat for a total of 5-6 minute contact time 6. Rinse gently 7. Dry Do not allow the surface to dry during application. Performance on bare aluminum: CHEMEON TCP-HF meets the electrical conductivity and adhesion test specifications in accordance with MIL-DTL-81706B and MIL-DTL-5541F (revision of MIL-C-5541E) When using the recommended process, corrosion resistance beyond 336 hours salt spray is obtainable. Although the coating is not as strongly colored as hexavalent chromate coatings, the trivalent SW CHEMEON Surface Technology All Rights Reserved 5

6 coating has a pale yellow to blue tint depending on the preparation steps, the alloy, and the processing parameters. TCP-HF Operation - Anodic Seal Anodized coatings sealed with TCP-HF exceed the requirements of MIL-A The bath chemistry (concentration, ph, temperature) used for anodize sealing may be the same as that used for conversion coatings, however the user may find it beneficial to adjust the concentration or immersion time depending upon their application. When used as an anodic seal, the operating parameters of TCP-HF are: TCP-HF 5-30% by volume (25-30% v/v suggested, adjust to avoid powdering) Time: 1 to 10-minute contact time (2-5 minute recommended, adjust to minimize powdering) Application as a seal: After anodize, rinse the parts thoroughly (2-5 minutes) to remove remaining acids from the oxide. A counter-flowing DI rinse is recommended. Immerse the parts in TCP-HF for 1 to 10 minutes (2-5 minutes is typically sufficient). The tank should not be agitated during sealing. After seal, rinse the parts in DI water. A second rinse should be sufficient. Gently blow dry or allow to air dry. Powder formation on the coating can be a result of: Immersion time too long Concentration too high Temperature too high For Type IIB anodize, best corrosion performance is found when the coating weight is in the upper third of the allowed range. Application on Other Materials Cadmium TCP-HF may be used as a post treatment on cadmium in lieu of the traditional hexavalent chrome products. Satisfactory wet tape epoxy primer adhesion and corrosion resistance (>192 and up to 1200 hrs) are achieved. Refer to the CHEMEON Steel Cleaner Technical Data Sheet for additional information. A typical process for cadmium would be: 1. 3 min CHEMEON Steel Cleaner, 130 F 2. 1 min tap rinse 3. 1 min DI rinse second 1% nitric acid dip, room temp 5. 1 min tap rinse 6. 1 min DI rinse 7. 5 min CHEMEON TCP-HF 28% v/v, room temperature 8. 1 min DI rinse SW CHEMEON Surface Technology All Rights Reserved 6

7 TCP-HF Operation Cadmium Post Treat by Immersion Concentration: TCP-HF 10-50% by volume (25-30% v/v recommended) Immersion time: 1 to 15-minute contact time (5-6 minute recommended) Magnesium When pretreated with CHEMEON s line of magnesium pretreatment products, magnesium can be coated with TCP-HF so that that it meets the requirements for GMW For further information on magnesium pretreatment, refer to the CHEMEON Magnesium Cleaner and CHEMEON Magnesium Activator Technical Data Sheets. A typical process for magnesium would be: 1. 5 minutes CHEMEON Magnesium Cleaner 20% v/v, 160 F 2. 1 min tap rinse 3. 1 min DI rinse seconds Nitric Acid, 10% v/v, room temp 5. 1 min tap rinse 6. 1 min DI rinse 7. 5 minutes Hydrofluoric Acid, 20 wt%, room temp* 8. 1 min tap rinse 9. 1 min Di rinse minutes CHEMEON Mg Activator, 30% v/v, 4.5 ph, very mild agitation min tap rinse min DI rinse minutes CHEMEON TCP-HF, 28% v/v, 3.8 ph seconds Di rinse * See AMS3171 and AMS-475 for non-hydrofluoric acid options. TCP-HF Operation Magnesium Immersion Concentration: TCP-HF 10-50% by volume (25-30% v/v recommended) Immersion time: 1 to 15-minute contact time (5-6 minute recommended) Post conversion coating processes paint, powder coat, etc. TCP-HF coated parts may be handled immediately after drying and are ready to mask or prime within 2 hours. TCP-HF coated panels have been painted with epoxy primer as long as 3 weeks after application of TCP-HF. The panels met all adhesion (wet tape, dry tape) requirements. Certain individual specifications state minimum and/or maximum times between conversion coat and paint the guidance in this technical data sheet does not supersede the times in the governing specifications. SW CHEMEON Surface Technology All Rights Reserved 7

8 Solution Control Bath maintenance: The ph of the bath should be checked regularly. It is important that the ph of the bath does not exceed 4.0. Measurement of the bath concentration may be performed by using spectrophotometry or by titration. Solution Control by Titration: The solution concentration may be ACCURATELY measured by titration. The trivalent chromium in the solution is oxidized to hexavalent chromium using hydrogen peroxide. The hexavalent chromium content is then measured using a redox titration. Required Materials Stirring hotplate 100 ml pipet Pipet bulb 50 ml burette 50 ml graduated cylinder Filter funnel Fine porosity filter paper (8 µm pore size recommended) 250 ml Erlenmeyer flask 10% w/w sodium hydroxide 35% hydrogen peroxide 17% v/v hydrochloric acid Potassium iodide Starch indicator solution Method: 1. Pipette 100 ml CHEMEON TCP-HF into a 250 ml Erlenmeyer flask. 2. Add approximately 20 ml sodium hydroxide solution. 3. Add approximately 5 ml hydrogen peroxide, stirring for 5 minutes. 4. Add another 5 ml hydrogen peroxide, stirring for an additional 5 minutes. 5. Boil the solution for 30 to 40 minutes to remove excess hydrogen peroxide. The solution will be highly effervescent at first. Be careful to avoid boiling the solution over. Do not allow the solution to evaporate below 50 ml. 6. Cool the solution and bring the volume to approximately 100 ml with deionized water. 7. Filter the solution through a fine-grained filter paper. Rinse the filter paper and precipitate using a wash bottle filled with deionized water until it is colorless. Retain the filtrate. 8. Important: the filtrate must not be cloudy. If the filtrate is cloudy it must be filtered again with a finer pore filter paper. 9. Make sure the titration apparatus is prepared. The burette should be prepared with 0.1N sodium thiosulfate. 10. Add 40 ml hydrochloric acid to the filtrate. The filtrate will turn from yellow to orange. 11. Add approximately 1 g potassium iodide. The filtrate will turn red. 12. Immediately titrate the solution with 0.1N sodium thiosulfate until the solution is pale redbrown. 13. Add 2 ml of starch solution and titrate to endpoint (mint green). SW CHEMEON Surface Technology All Rights Reserved 8

9 Concentration Calculation: Conc. CHEMEON TCP-HF (% by vol.) = (volume in ml of 0.1N sodium thiosulfate used) x 1.01 Solution Control by Spectrophotometry Summary The TCP-HF solution has a peak absorption at approximately nm. This peak can be used to measure the concentration using a Beer s Law Plot. An accurately quantified primary standard is created from concentrated TCP-HF by titration. Three secondary standards are then created by dilution of the primary standard. The secondary standard concentrations are chosen so that they bracket the nominal TCP-HF concentration. The peak absorbances of the standards are measured and plotted as a function of concentration. The concentration of an unknown can then be determined by measuring the absorbance and comparing it to the plot of known standards. If you need assistance, please call the CHEMEON Tech Center at for a Microsoft Excel spreadsheet that will help you calculate the concentration. Equipment: Spectrophotometer capable of measuring absorbance at nm Quartz or plastic cuvettes Plastic pipettes Adjustable volume precision pipettor or equivalent volumetric pipettes (Class B glassware is acceptable though Class A is more accurate) 100 ml volumetric flasks Plastic storage bottle for primary standard Fine porosity filter paper x 1 per bath sample (8 µm pore size recommended) Prepare the primary standard Using concentrated TCP-HF, prepare a solution that is roughly twice the nominal (target) operating concentration. In other words, if the target operating concentration is 28%, make a solution using TCP-HF concentrate at 50-60%. The mixture does not have to be exact, it will be analyzed in the next step. It is suggested that at least 1 liter of solution is made. Analyze the mixture using the titration method described above. It is recommended that duplicate or triplicate analyses are performed to ensure accuracy. This is now the primary standard. Store it in an air tight plastic bottle, and it will be able to be used more than once. Label it appropriately (concentration, date, substance). Test the solution by titration every month or so (depending upon the customer s method of storage) to make sure the concentration has not drifted. If the concentration drifts over time, simply re-analyze by titration. Once the concentration is accurately known, use the solution to make UV-Vis secondary standards by dilution. SW CHEMEON Surface Technology All Rights Reserved 9

10 Procedure for secondary standards by dilution: Three (3) standards must be prepared. One near the nominal bath concentration, one above the nominal bath concentration, and one below the nominal bath concentration. a. Three standards are sufficient, more may be prepared but are not necessary. b. The standards do not have to be close to the concentration of TCP-HF. However, it is very important that the high and low standard bracket the bath concentration. Example: for an expected bath concentration of 28%, it is acceptable to use a 10% to 20% lower standard, a 20-30% midrange standard, and a 30 to 50% upper range standard. c. Sample response is very linear for this chemical, and modern UV-VIS machines can handle a wide range of absorbances without issue. d. Prepare volumetric standards that bracket the expected TCP-HF concentration. e. Rather than try for an exact concentration, use dilutions that are simple to perform. Example: Assume the primary standard is at 48% by volume as measured by titration and the anticipated bath concentration is 28% i. In 100 ml total volume (volumetric flask) ii. Add 25 ml of the primary standard using a pipet, fill to the mark with water. iii. The concentration of this standard is!"#$ 48% = 12% by volume %&&#$ iv. Similarly, a mid-range standard at 24% by volume is created using 50mL of the primary standard in a total of 100 ml v. The primary standard itself can be used as the upper range standard at 48% Best Practices are to make the secondary standards on the day of each analysis. They may be saved and reused, although this practice is discouraged. The Primary standard may be saved and re-used. The concentration of the primary standard should be checked periodically (by titration) to ensure the calibration is still valid. Notes on accuracy: While a graduated cylinder could, in theory, be used instead of a pipettor or an array of pipettes, in practice the graduated cylinder is much less accurate. Inaccurate glassware introduces unwanted inaccuracies in the calibration and ultimately may adversely affect the bath performance. Procedure for analyzing CHEMEON TCP-HF bath sample: 1. Turn on the spectrophotometer. Allow the instrument to warm up according to manufacturer s specifications. 2. Filter approximately ml of the bath sample through fine porosity filter paper. 3. Set the wavelength of the spectrophotometer to the absorbance maximum between 595 and 605nm. This wavelength should be determined ahead of time with a sample of TCP- HF. 4. Fill the cuvette with deionized water and wipe down the outside walls of the cuvette so they are free of fingerprints, streaks, and moisture. 5. Place the cuvette in the spectrophotometer and zero the instrument according to manufacturer s specifications. 6. Measure the absorbance value of the deionized water according to the manufacturer s specifications. Record this value. It should be very close to zero. 7. Using a clean plastic pipette, refill the cuvette with one of the previously prepared CHEMEON TCP-HF standards, clean the walls of the cuvette again then place it in the spectrophotometer. 8. Measure and record the absorbance value. SW CHEMEON Surface Technology All Rights Reserved 10

11 9. Repeat steps 4 through 8 for the other two standards and the filtered bath sample. 10. Plot the absorbances of the standards as a function of concentration (i.e. a Beer s Law Plot), obtain the equation of the line that best fits the data. This is easily done in Microsoft Excel. Contact the CHEMEON Tech Center for a spreadsheet that will help process the data. 11. Use the equation of the line to determine the bath sample concentration. 12. Note these steps describe a basic method for obtaining the absorbance values. Many newer instruments have calibration methods built in. Please consult your operation manual for the correct method of calibration. Bath Additions: To maintain the target operating concentration, first measure the bath concentration (C) by titration or spectrophotometry. Once the concentration is measured, subtract this bath concentration from the target. The resultant difference can now be multiplied by the tank volume to obtain the necessary addition amount. [ (Target% - C%) /100 ] x tank volume = amount of CHEMEON TCP-HF concentrate to add Tank volume and TCP-HF amount will have the same units (gallons, liters, etc.) SAFETY AND HANDLING Prior to handling and use of any of the materials referenced in this document, the Safety Data Sheets should be read and understood by all personnel in contact with these materials. Eyes and skin should be protected with appropriate personal protective equipment. Do not ingest. Having eyewash fountains and emergency showers in close proximity is recommended. KEEP OUT OF REACH OF CHILDREN STORAGE Store CHEMEON TCP-HF in dry, indoor storage at temperatures between 35 F and 95 F. Do not allow to freeze. Keep the product away from any incompatible materials referenced in the Safety Data Sheets. All containers should be tightly closed when not in use. SHELF LIFE Product shelf life is a minimum of 12 months from date of manufacture as tested per section 3.9 of MIL-DTL CHEMEON laboratory testing supports a 24-month shelf life from date of manufacture. DISPOSAL Any disposal of the materials referenced in this document should be in accordance with all applicable federal, state, and local regulations. The process solution can contain components other than those present in the materials as supplied. Analysis of process solutions may be required prior to disposal. SW CHEMEON Surface Technology All Rights Reserved 11