CLEARLYTE PLUS CATHODIC ELECTROPHORETIC CLEAR / TINTED CLCQUERING PROCESS

Transcription

1 CLEARLYTE PLUS CATHODIC ELECTROPHORETIC CLEAR / TINTED CLCQUERING PROCESS Introduction Clearlyte Plus is an advanced version of the earlier popular electophoretic Clearlyte lacquer. It is a water-based lacquer which gives a clear protective coating on metal articles. Clearlyte Plus is cathodically electrodeposited. After curing the deposit, excellent gloss and image clarity is obtained. Components can be transferred directly from the final electroplating process stage through rinses to Clearlyte Plus without the need for an intermediate drying state. Clearlyte Plus shows an excellent throw into recesses and gives uniform deposit thickness. No runs and tears are observed and high corrosion and chemical resistance are obtained. CLEARLYTE PLUS GIVES : Better Gloss Better Throwing Power Higher concentration (50% solids) as against earlier equivalent (30% solids) Cost reduction of approximately 20% as per current prices Can be used for low-build deposits of 3 to 4 microns as also for higher thickness upto 20 microns Imparts a richer gold shade (Similar to 24 Karat Gold Finish) when used in conjunction with Clearlyte Gold dye. Process Sequence : In outline the sequence is : Pre-treatment-application of Clearlyte Plus post treatment-stoving. The pre-treatment is required to ensure absolute cleanliness and to obtain a swlaco-free from water breaks. Articles which have been electroplated should end up with a cold water rinse. Mechanically polished or untreated articles should be cleaned using the appropriate treatments. CLEARLYTE PLUS 1

2 A typical process sequence is : *Growclear Prepas 4V 1 min. water rinse Demineralised water rinse, twice. Pre-dip in dematerialized water with 20ml/ltr. Clearlyte Plus bath solution or ultrafiltrate permeate rinse. Clearlyte Plus plate Post rinse in pure ultrafiltrate (permeate). Demineralised water rinse, alongwith 1 ml/ltr. Growclear RA, twice. Air dry (60 70ºC, approx. 10 min.). Cure ( ºC, approx. 25 min.). *Growclear Prepass To reduce the colour change on brass/satin nickel coated components. The purpose of the dematerialized rinses is to prevent the lacquer solution from being contaminated. The pre-dip in dilute lacquer permeate dip is considered essential in order to prevent film defect caused by gassing. The post-rinse is used to remove the lacquer solution from the coated object. Although a separate pre and pot-rinse is recommended, it is possible to use the pre-rinse also as post-rinse in running ultrafiltrate permeate rinse. PROCESS EQUIPMENT : A full range of specially developed equipment is available form Growel. All tanks in contact with lacquer solution should be suitable plastic construction or of steel with acid and solvent resistant lining such as polypropylene. TANK : The Clearlyte Plus working tank should be fitted with : An overflow compartment. A circulating pump with circulation capacity of at least 5 times tank volumes per hour. A filter, preferably equipped with a bypass system for optimum circulation, with a 1-3 micron cartridge. A low energy heater (quartz) whenever required, especially in the north during winter season in India. A cooling coil or Teflon or stainless steel 316 grade protected form direct current is necessary to maintain temperature at the optimum level. Stainless steel anodes are used grade 316. ULTRAFILTRATION The use of an ultrafiltration unit has proven to be an integral part of successfully operating Clearlyte Plus baths. Every installation should have a UF unit. The use of ultrafiltration helps to minimize the effect of metallic contamination and stabilizes the ph of the solution. OVEN Recirculatory hot air ovens or tunnel should be used. A gradual increase in temperature up to 140ºC for a partial curing and 150ºC to 180ºC for a fully cross linked cure is ideal. An excellent system is a conveyor oven with temperature zoning in which the parts are heated slowly to the curing temperature. RACKS Normal PVC plastisol coated racks can be used. In practice is it found that if the rack is used in an electroplating line with an alkaline cleaning sequence then it is not necessary to remove the lacquer from the rack contact. It is strongly recommended to use adequate ventilation equipment for the Clearlyte Plus and the working area. CLEARLYTE PLUS 2

3 It is very important to maintain a clean working atmosphere in the shop. Any dust or floating shop soils will settle on Clearlyte Plus bath and will deteriorate the final finish. It is certainly advisable to install Clearlyte Plus plant in cool and dust-free room. PROCESS MAKE-UP All dematerialized rinses should be filled with dematerialized water with a conductivity of less than 5µs. The pre-rinse is pre-rinse is prepared by adding 20ml/ltr. Clearlyte Plus bath solution to dematerialized water. Ensure that the ph of the pre-rinse is the same as the Clearlyte Plus bath. The pre and post-rinse can be replaced with clean demineralised water or ultrafilter permeate which will be gradually contaminated with the solution from the Clearlyte Plus bath, specially post-dip. Clearlyte Plus working solution : The Clearlyte Plus concentrate as supplied should be diluted with dematerialized water in the ratio of 1 part concentrate to 2 parts of dematerialized water by volume. This gives a solid content (nonvolatiles) of 9.9% by weight. In case of Clearlyte Plus tinted dyes, select the dye and add 10 to 12 ml/ l in concentrate Clearlyte Plus resin and dilute with dematerialized water up to resin make-up. The recommended procedure is to add the water to the concentrate with constant mixing. The dematerialized water should have a conductivity of less than 5 µs. A low speed electric stirrer is the ideal equipment for thorough mixing. The new bath must be circulated and / or stirred to 48 to 72 hours before use. This ageing must be carried out with the cover off the tank all the time and with a bath temperature of 25 to 28ºC. Watch the solution level in the weir compartment. The use of an ultrafiltration unit will speed the ageing of the solution. It is not advised to measure the ph immediately after make-up of the new solution, but after the first 48-72hrs. of stabilization. No alkali must be added to the Clearlyte Plus solution. OPERATING CONDITIONS CLEARLYTE PLUS Solution Circulation - Continuous - not essential at weekends. For holidays transfer to closed containers. ph (Electrometric) Conductivity µs. at 25 o C and 10-12% solids content. MEQ (Add Growclear ES 1 ml/l to increase 10 MEQ. Voltage volts, maximum ripple 20% Cathode current density - Average A/dm. sq. Surge A/dm sq. (do not exceed 0.5 A/dm 2 ) Cathode/anode area - Do not operate with an anode area greater than the cathode area. Deposition rate - Deposition is fast, during first few seconds, then slows down, giving typically 8 microns in the first 30 seconds. CLEARLYTE PLUS 3

4 Process Time - Variable between 10 and 120 seconds. Allow a dwell time of 10 to 15 seconds before switching on the current. Curing - CLEARLYTE PLUS will be fully cured by stoving at a metal temperature of 155 o C. for 20 minutes. It is essential that the metal components are at the curing temperature for the full 20 minutes. Temperature range is 150 o C to 180 o C. Temperature o C.,Optimum 28 o C. Temperature may be allowed to fall to 15ºC. during long closed down periods. *Dyes - Fourteen Colour Shades are available for process in tank dyes in Clearlyte Plus resin. *Post Dyes - Different post dyes are possible after Clearlyte Plus coating. Refer post dyes literature for more details. *Consult G & W local TSD for your specific dye requirement. PROCESS MAINTENANCE : Dematerialized Rinse : The dematerialized rinses before lacquering, serve to minimize drag-in of hard water salts and pre-treatment chemical into the Clearlyte Plus solution and thereby prevent it from being contaminated. After lacquering, it serves as a clean final rinse. The rinse should be dumped when the conductivity exceeds 25µs. Post-rinse : This solution gradually becomes contaminated by drag-in from the Clearlyte Plus bath. It should be replaced periodically or when the solids content reaches 1.5% by weight. Solution Level : Water is lost by evaporation, the level in the overflow section should be restored regularly by adding dematerialized water. Watch the solution level in the weir compartment, do not let the pump suck air. Do not use the post-rinse solution for topping up. Solid Content : A freshly prepared Clearlyte Plus bath contains 9.9% by weight solids. The concentration will need to be increased up to 13% after the first working days. Clearlyte Plus concentrate should be used to obtain and maintain this solids content. The best method of addition is to premix the requir4d amount of concentrate with the working solution in a separate container. Never add the concentrate directly to the bath. Preferably additions are done at eh end of production day. Consumption is dependant on drag-out and film thickness, generally 1 lt. concentrate for 25m 2 with 5 8 microns. Normally the solids content should be determined once or twice a week. Solvent Content : Solvent is lost by evaporation and drag-out. Normally the solvent level is maintained by the addition of Clearlyte Plus concentrate. If solvent additions are necessary, following long idle periods for example, they should be made in increments of 0.5% through the weir. It takes about one to two hours of solution circulation before the effect becomes apparent. Solvent level should be determined once a week. ph : the ph of the bath should be lie between Clearlyte Plus as supplied has a ph value within this range so that a freshly prepared bath has the correct ph. It is good practice to check the ph once or twice a week. It is not advised to use ph paper for ph measurements. CLEARLYTE PLUS 4

5 Ionic Contamination : Avoid contamination of the Clearlyte Plus bath by soluble salts. They will decreases the efficiency, leading to bad deposits. Only with ultrafiltration can the ionic contamination be removed (slowly) by discarding the permeate. Adequate circulation and filtration will keep the lacquer in a fit condition. Filter cartridge will be clogged up with use. They should be cleaned or changed periodically. The circulation pump should not suck air, any air getting into the circulation system will cause pitting. It is recommended to carry out a batch filtration, followed by tank cleaning every one or two months. During prolonged idle periods tank circulation can be stopped, the cover of the tank must be closed. Alternatively, the bath solution can be stored in closed containers. Ultra filter equipment and filters should be flushed out with dematerialized water and left filled with dematerialized water. TROUBLE SHOOTING : PROBLEM POSSIBLE CAUSES RECOMMENDED ACTIONS 1. Thick deposit Voltage too high Reduce voltage Temperature too high Operate at 23 to 28 C Plating time too long Reduce plating time 2. Orange Peel Solvent too high Purge with ultrafiltration High surge current Reduce voltage 3. Thick, rough / Initial surge current too high Lower surge current to less than uneven film 3A/ft 2 (0.3 A/dm 2 ) Reduce anode area Temperature too high Reduce temperature Ionic Contamination Purge with UF unit 4. Thin deposit Voltage too low Increase voltage Plating time too short Increase plating time Solid / Solvent too low Analyze and adjust solid/solvent level 5. Thin film with high Solid/Solvent too low Analyze and adjust solid/solvent level density pitting Temperature too low Operate at 23 to 28 C 6. Iridescent deposit Deposit too thin Increase voltage and/or plating time Temperature too low Operate at 23 to 28 C 7. Thin patchy deposit Solvent too low Analyze and adjust solvent level Solids too low Analyze and adjust solid level ph too low Check ph 8. Rough, spotty Metallic contamination Strip lacquer coating and check scattered pits substrate condition Purge with UF Unit Dirty, dusty oven Clean oven thoroughly Insoluble particles Batch filter followed up with ultrafiltration Poor quality rinse water Use deionized water with a conductivity of less than 5 Micro Siemens 9. Water breaks Solvent too high Purge with UF Unit during Post-rinsing 10. Water Marks after Incorrect or insufficient post- Prepare fresh Growclear RA solution curing rinsing Incorrect drying procedure Refer to drying procedure CLEARLYTE PLUS 5

6 11. Gas Pits / Voids Too much aeration in the Switch off pumps and allow solution to clear solution Check for air suction Correct pump problem and use gentle agitation; minimize aeration and foaming actions Incomplete wetting of parts Refer to pre-rinsing procedure surface prior to plating 12. Soft deposit; Low curing temperature Cure at metal temperature of 154 to 180 C poor chemical Insufficient curing time for 20 to 30 minutes resistance Increase curing time 13. Darker/discoloration Curing temperature too high Decrease curing temperature 14. Low gloss / hazy Deposit too thick Reduce voltage deposit Solvent too low Analyze and adjust solvent level Contamination Purge with UF Unit 15. Inconsistent Quality Irregular or large additions Make smaller, regular additions of of solids and/or solvent Clearlyte Plus Insufficient mixing time Allow one to two hours of solution after solids or solvent circulation after each Clearlyte Plus additions addition or 30 min. circulation after each solids addition 16. Light brownish- Polymerization of resin due Agitation / filtration Yellow solution to localized heating Use low watt density heaters (Less than 3 watt/in 2 ) Solution temperature high Operate at 23 to 28 C 17. Pinkish solution Solvent too low Analyze and adjust solvent level 18. Slow amerage drop Solvent too high Purge with ultrafiltration during coating 19. Poor throwing power Incorrect anode-to-cathode Use 1:5 minmum or 1:2 maximum ratio anode-to-cathode ratio 20. Solution ph falling Contamination from cleaning Ultrafiltration predip solution for cycle and pre-dip approximately 8 to 12 hours and discard the permeate generated Replace a portion of the solution with new Clearlyte Plus solution if the problem is serious 21. Solution ph rising / Drag-in of alkaline Purge with ultrafiltration precipitation of resin contamination Add 1 ml/l Growclear ES and work 22. Low conductivity Low solids Analyze and adjust solids (Less than 550 Low solvent Analyze and adjust solvents micro siemens) 23. High conductivity High solids Reschedule replenishement (Greater than 950 High solvents Reduce voltage micro siemens) Ionic contamination Purge with ultrafiltration CLEARLYTE PLUS 6

7 GROWCLEAR STIRIPPER : For defective elctrophoretic lacquer coated component can be stripped in Growclear Stripper without affecting the undercoat. This is ready to use product. After stripping with this product, normal cleaning activation cycle and applied before recoating in electrophoretic lacquer. ANALYTICAL PROECEDURES : 1. Solids content determination : - Weight a clean watch glass or aluminium foil. - Add 10 ml of Clearlyte Plus solution. - Stove in the oven for 2 hours at 165ºC - Cool and re-weight. - Calculate the % solids content by weight difference. For each 0.3% solids required add 1 lt. Clearlyte Plus concentrate per 100 lt. of working solution. on the spot solids content determination, a pocket refractometer can be used : % solids (by weight) = 0.73 x Reading (O Brix) 2. Solvent lever determination. For each analysis of the solvent level contact Growel. 3. ph measurement : - calibrate ph meter - Rinse elctrodes in dematerialized water, dry and immerse in Clearlyte Plus. - After measuring, thoroughly rinse electrodes in Clearlyte Plus solvent and finally rinse in dematerialized water again. WASTE DISPOSAL Clearlyte Plus solution Increase ph of the solution 7 8 with alkali. The solids will precipitate out in the settlement tank. Supernatant liquid will contain about 4% by volume solvent and lactic acid. This liquid should be further diluted before discharge to meet local authority laws. For more details see MSDS. Issued on Supersedes all earlier CLEARLYTE PLUS 7