Enviralloy Ni High alloy, alkaline zinc nickel process

Transcription

1 Enviralloy Ni High alloy, alkaline zinc nickel process Typical Advantages High cathode efficiency Ease of use Uniform alloy distribution

2 Enviralloy Ni /07/2005 Page 2 CONTENTS SECTION PAGE NO. 1. Technical Advantages 3 2. Value In Use 7 3. Operating Manuals 9 4. Passivation Coatings & Top Coats Process Conversions 43 Products and Codes for the Enviralloy Ni System Products Codes Enviralloy Ni A IP Enviralloy Ni B IP Enviralloy Ni C IP Enviralloy Ni D IP Enviralloy Replenisher IP Envirowetter IP 74371

3 Enviralloy Ni /07/2005 Page 3 1. Technical Advantages Enviralloy Ni is an electroplating process designed to deposit a zincnickel alloy containing 12-15% nickel, 85-88% zinc, on to steel substrates. The passivated deposit is highly resistance to corrosion, providing over 1000 hrs of Neutral Salt Spray resistance from a 10 micron deposit. It is suitable for both hexavalent and trivalent passivation treatments in clear, iridescent, yellow and black colours. Zinc-nickel is particularly effective at preventing corrosion in applications where repeated thermal shock or thermal cycling are important, as the coating is not significantly affected by prolonged or repeated heating at temperatures up to 200oC (390oF). The system can be used in both rack (individual) and barrel (bulk) application equipment. The Enviralloy Ni system has the following principal technical advantages: Higher Cathode Efficiency & Plating Rate Resulting in shorter plating time to deposit required minimum thickness. Uniform Alloy Distribution Resulting in a more consistent corrosion performance. Excellent Deposit Distribution Resulting in lower cost to deposit minimum thickness. Consistently High Nickel Alloy Content Resulting in accurate compliance to specification.

4 Enviralloy Ni /07/2005 Page 4 um per Hour Plating Rate Enviralloy Ni at various cathode efficiencies (standard Hull Cell panel 1A) 70% CE 50% CE 35% CE Amps per square decimetre Alloy Distribution Enviralloy Ni at various current densities (standard Hull Cell panel 1A) 14.5% 7.5 g/l Zn 8.5 g/l Zn 14.0% % Ni in Alloy 13.5% 13.0% 12.5% 12.0% Amps per square decimetre

5 Enviralloy Ni /07/2005 Page 5 % Ni in Alloy Alloy Distribution Enviralloy Ni compared to: competitor 12% alloy (C12%) & competitor 6% alloy (C6%) (standard Hull Cell panel 1A) C6% C12% Enviralloy Ni % 14% 13% 12% 11% 10% 9% 8% 7% 6% 5% Amps per square decimetre um per minute Deposit Distribution Enviralloy Ni compared to: Acid Chloride zinc-nickel process (standard Hull Cell panel 1A) Acid ZnNi Enviralloy Ni Amps per square decimetre

6 Enviralloy Ni /07/2005 Page 6 % Ni in Alloy 21% 19% 17% 15% 13% 11% 9% 7% 5% Alloy Distribution Enviralloy Ni compared to: Acid Chloride zinc-nickel processes (standard Hull Cell panel 1A) Acid ZnNi Enviralloy Ni Amps per square decimetre Note: The above graphs were generated from an Enviralloy Ni prepared to the following standard: Test solution Zinc metal 8.5 g/l Nickel metal 1.1 g/l Ratio Zn:Ni 7.7:1 Sodium Hydroxide 110 g/l Replenisher 10 ml/l Part A 25 ml/l Part B 40 ml/l Part C 20 ml/l Part D 6 ml/l Wetter 0.5 ml/l Sodium carbonate < 10 g/l Temperature 24 C

7 Enviralloy Ni /07/2005 Page 7 2. Value in Use Process Cost Analysis A comparison to deposit an average of 8um zinc-nickel on a surface area of 100m 2 meters. An average current density of 2.5 Adm -2 (25 A/ft -2 ) was applied. Zinc metal and additive consumption s were calculated and the costs compared with the following plating systems. Comparison with Competitor Systems Enviralloy Ni Competitor 12% Alloy process Competitor 6% Alloy Process Time 26 mins 32 mins 40 mins Amp Hours Consumed 10.8 kah 13.2 kah 16.7 kah Zinc Consumed 5.1 kg 5.1 kg 5.4 kg Zinc Cost unit / Kg Zinc Cost 459 units 459 units 468 units Nickel Consumed 0.74 kg 0.74 kg 0.31 kg Nickel Cost unit / Kg Nickel Cost 746 units 746 units 312 units Total Metal Cost 1209 units 1209 units 780 units Brightener Consumed lt 2.6 lt 2.3 lt Brightener units / ltr Brightener Cost Carrier Consumed lt 3.0 lt 0.8 lt Carrier units / ltr Carrier Cost Booster Consumed lt 0.5 lt Booster units / ltr Booster Cost LCD add Consumed 2-1.3lt 0.7 LCD add units / ltr LCD add Cost Replenisher 0.32 lt - - Consumed Replenisher 2 units / ltr Replenisher Cost Additive Cost 1,442 units 3,330 units 2,361 units Total Cost 2,651 units 4,539 units 3,141 units Electricity Consumed 109 kwh 134 kwh 168 kwh Cost per 1 kwh 4.2 Cost Electricity 457 units 562 units 705 units Total Cost 3,108 units 5,101 units 3,846 units Material cost differences of Competitor systems Vs Enviralloy % + 19 % Data Based on: Typical selling price of NiSO4.6H2O derived from LME price (November 2002 & MacDermid / competitor datasheets.

8 Enviralloy Ni /07/2005 Page 8 Based on the calculations in the previous tables, to plate the reported parts, Enviralloy would offer the following advantages: Versus: Competitor s High Alloy alkaline zinc-nickel processes The potential to reduce plating times by a minimum of 20% to achieve a minimum thickness More economical when compared to a leading competitors systems Reduction in electricity consumption to achieve an equivalent deposit thickness More even alloy distribution Easier to operate Versus: Low Alloy metal alkaline zinc The potential to reduce plating times by a minimum of 35% to achieve a minimum thickness A saving of more some 40% in system additives Reduction in electricity consumption to achieve an equivalent deposit thickness Easier to operate N.B. Low alloy zinc-nickel systems can be used to produce deposits with greater ductility that high alloy systems, thus proving advantagous over high alloy content deposits.

9 Enviralloy Ni /07/2005 Page 9 3. Operating Manual Introduction Enviralloy Ni is a high performance alkaline zinc-nickel system that is formulated to meet market demand for zinc-nickel alloy contents up to 15%. When used as recommended, it produces an alloy of zinc-nickel containing 12 15% nickel. The deposits are semi-bright and can be easily passivated in either trivalent or hexavalent systems. Finishes that can be obtained range from blue/grey to black. Please refer to the latest Enviralloy Ni technical data sheet for recommended operating parameters for this process.

10 Enviralloy Ni /07/2005 Page 10 System requirements There are certain plant and pre-treatment requirements that must be adopted to ensure the successful operation of this process. This applies equally to manual and fully automated plants: 1) Alkaline zinc-nickel plating are more susceptible to pre-treatment faults when compared with more conventional plating systems (i.e. cyanide zinc or cadmium) and the pre-treatment sequence must reflect this (See Pre-treatment Section). 2) It is essential to maintain a consistent zinc concentration in the plating solution. For alkaline zinc-nickel this is best achieved using a suitable zinc generator. (See Zinc Generator Section) 3) The Enviralloy Ni additives maintain the brightness, distribution and nickel content of the zinc-nickel deposit. The level of these additives must be maintained in the plating solution by means of ampere-hour controlled dosing pumps. This will ensure that a consistent finish is achieved. 4) The plating solution should be filtered. It is recommended that the filter unit be sited in the zinc-nickel generator circuit. 5) The solution should be heated to the operating temperature after plant shutdowns and chilled to prevent overheating whilst in operation. Heaters should be of mild steel construction. 6) Mild agitation of the solution is recommended in order to achieve optimum performance. Cathode rod agitation or plating solution movement via eductors is recommended. 7) Analytical control of both the plating solution and the plated deposit are essential for correct operation of the process. The minimum that any potential user must have access to should be: Volumetric analysis equipment (Zn, NaOH) X-Ray Fluorescent spectrometer (Alloy Content, Deposit Thickness) Atomic Absorption or UV/VIS Spectrophotometer (Ni Content)

11 Enviralloy Ni /07/2005 Page 11 Cleaning Failure to observe correct pre-treatment prior to alkaline zinc-nickel plating can result in poor quality deposits and in extreme circumstances, imperfect adhesion. It is important to transfer components from the final pre-treatment stage to the zinc-nickel plating solution quickly, thereby preventing the formation of any surface oxides. The benefits of a good pre-treatment regime can be completely negated by allowing the parts to become oxidised just prior to plating. The preferred cleaning sequence is given below. 1) Soak clean 2) Anodic clean 3) Rinse X 2 4) Acid pickle (Inhibited 50% HCl or Heated H 2 SO 4 ) 5) Rinse X 2 6) Anodic clean (Alkaline Deruster Salts or equivalent) 7) Rinse X 2 8) Zinc-nickel plate The sequence has been developed to avoid contamination of the plating solution with chlorides or oils. It also ensures the best adhesion of the zinc deposit to steel. If you wish to use an alternative pre-treatment cycle please confirm its suitability with your local technical manager or the global functional group.

12 Enviralloy Ni /07/2005 Page 12 Plating Details of the preparation of the plating solution and basic operation are covered fully in the Enviralloy Ni Technical Data Sheet. Under normal operation the solution should plate 16 microns average deposit thickness per hour between 2.2 and 2.8 Adm -2. The table below outlines the recommended ranges for the plating solution operating parameters. Parameter - Rack Range Metric US Zinc concentration g/l oz/gal Nickel metal concentration g/l oz/gal Zinc metal : Nickel metal ratio 6:1 to 10:1 6:1 to 10:1 Sodium hydroxide concentration g/l oz/gal Sodium hydroxide : Zinc ratio 15:1 to 20:1 15:1 to 20:1 Replenisher concentration 10 ml/l 1 % Cathode current density 1.5 to 2.5 Adm Aft -2 Bath temperature 20 o C to 28 o C 68 o F to 82 o F Parameter - Barrel Range Metric US Zinc-nickel concentration g/l oz/gal Nickel metal concentration g/l oz/gal Zinc metal : Nickel metal ratio 6.5:1 to 10:1 6.5:1 to 10:1 Sodium hydroxide concentration g/l oz/gal Sodium hydroxide : Zinc ratio 12:1 to 16:1 12:1 to 16:1 Replenisher concentration 10 ml/l 1 % Cathode current density 0.3 to 1.0 Adm Aft -2 Bath temperature 20 o C to 28 o C 68 o F to 82 o F

13 Enviralloy Ni /07/2005 Page 13 Zinc For each installation there will be an optimum zinc and nickel concentration for operating the process. This will depend on the type of components being processed and the way they are racked. Once this zinc concentration has been established it should be kept to within 1g/l of this optimum value. Generally, wherever there is the need for bright throwing power into very low current density areas on rack installations it is necessary to operate the process with lower zinc concentrations. For barrel plating installations where speed and efficiency of plating is important higher concentrations of zinc (8.5 to 10.5g/l / oz/gal) are required. The advantages and disadvantages of operating at lower concentrations of zinc are given in the table below. Low Zinc - Advantages Improved bright throwing power Increased rack loading capability Improved deposit distribution Low Zinc - Disadvantages Slower plating rates Reduced operating window Sodium Hydroxide The sodium hydroxide to zinc-nickel ratio governs the bright throwing power of the plating solution. However, the concentration of the sodium hydroxide is limited to a maximum of 130 g/l (17 oz/gall). This is because higher concentrations of sodium hydroxide will hydrolyse the organic additives at an accelerated rate. This makes solution maintenance less economical to operate and the increased solution density (i.e. viscosity) decreases plating efficiency. For almost all rack plants a concentration of about 110 to 120g/l ( oz/gall) and for barrel plants 110 to 130 g/l ( oz/gall) of sodium hydroxide should be suitable. Nickel Metal It is essential that the nickel metal is maintained in ratio to the total zinc concentration in order to maintain the correct alloy deposit (& distribution) and maintain the brightness of the deposit (particularly at low current densities). The optimum ratio of zinc:nickel is 6:1 to 10:1 in rack and 6.5:1 to 10:1 in barrel, depending on the deposit alloy content required. Lower ratios maintain higher nickel deposit content. Ratios higher than 10:1 can result in LDC burning and streaking.

14 Enviralloy Ni /07/2005 Page 14 Cathode current density For rack operation 1.5 to 2.5 Adm -2 (15 25 Aft -2 ) is recommended. At these current densities the bath should be capable of producing over 0.25 microns per minute average deposit thickness. Higher current densities (>3 Adm -2 ) leads to higher plating rates, but reduced plating efficiencies. Lower current densities give improved plating efficiencies but may lead to poorer distribution and bright throw into low current density areas. For barrel operation the solution efficiency is normally higher (than with rack plating). A bath operating at 0.5 Adm -2 should plate an average of up to microns per minute and at 0.8 Adm -2 should plate up to an average of 0.15 microns per minute. Note: Enviralloy Ni produces a tenacious organic film at the surface during plating. Due to the nature of this film it is not recommended to interrupt the current during the plating process. Switching off the current and then restoring it again later may result in laminated deposits. Rectification Rectifiers should be 12V for rack plating and 16V for barrel plating. As for all electroplating systems, current ripple should not be allowed to exceed 5%. Solution temperature It is essential to maintain a solution temperature between 20 o C and 28 o C (68 F 82 F) in order to maintain a bright deposit with good alloy distribution. Operating at higher temperatures will result in increased consumption of organic additives, dullness in low current density areas. Low temperature (< 20 o C / 68 F) results in lowered plating efficiency, burning and poor deposit adhesion. For most installations this will occasionally involve the use of heaters and the use of a refrigeration plant to cool the zinc-nickel solution whilst in production. Zinc-Nickel Ratio Vs Alloy Composition Alloy Composition Ratio 12-15% nickel 10:1 to 8.5: % nickel 7:1 to 8:1

15 Enviralloy Ni /07/2005 Page 15 Enviralloy Ni Additives Under normal operation, the Enviralloy Ni process employs four maintenance additives; Part B, Part C, Part D and Replenisher. A (IP74351) Part A is responsible for the solubility of the nickel in the plating solution and promote uniform nickel distribution in the plated alloy. It is generally only used in either preparation of a new solution or during conversion from a competitors system. If the solution is maintained as recommended, the concentration of Part A is maintained by additions of Part C. Part B (IP74352) Part B is added to maintain the excellent low current density performance of the system. It is consumed by drag out only and a recommended addition rate is 4 8 litres / 25 kgs of caustic soda added to the plating solution. Part C (IP74353) Part C contains both the nickel metal and the correct maintenance ratio of Part A. 1 ml/l (0.1 %) of Part C will raise the nickel content in the plating solution by 66 ppm. It is maintained by ampere hour dosing at the rate of litres / 10 kah rack, and litres / 10 kah barrel. Actual rates will vary depending on cathode efficiency, % nickel deposited and drag out. Higher efficiency levels, drag out and % nickel deposited will consume more part C. (See Graph 1) Part D (IP74354) Part D is the main brightening component and is particularly responsible for grain refining at high current density. It is maintained by ampere hour dosing at the rate of litres / 10 kah. Envirozin Replenisher This material is required to obtain a fully clear, bright deposit across the full current density range. Low Drag out and low water quality will dictate the use of this material. For optimum performance a newly made up bath will require 10 ml/l (1%), as the solution ages higher concentrations may be required. It is added back to the tank in ratio with sodium hydroxide. Recommended addition is 2 3 litres / 25 kgs. Envirowetter Envirowetter is used to reduce caustic spray and lower surface tension. Lack of wetter in the plating solution may cause pitting of the deposit.

16 Enviralloy Ni /07/2005 Page 16 Graph Ni 12% Ni 15% Litres of Part C per 10k A-H Bath Efficiency

17 Enviralloy Ni /07/2005 Page 17 Analysis Enviralloy Ni should be analysed frequently to determine the concentrations of zinc, nickel and sodium hydroxide in the plating solution. 1) Zinc / Caustic can be analysed by AAS or by one of the following volumetric methods: Method 1a - Zinc and caustic together Reagents 0.1N EDTA N H 2 SO 4 BDH 1113 indicator EDTA indicator solution ph 10 buffer solution 4% Formaldehyde solution Sodium cyanide a) Take a 5ml sample of solution and dilute to 10 ml with water b) Titrate with N H 2 SO 4 using MacDermid 1113* indicator to a yellow end point. c) Concentration of NaOH g/l = mls N H 2 SO 4 X 8 d) To this solution add 20ml of ph 10 buffer solution containing 10g/l NaCN. e) Add a few drops of EDTA indicator solution. f) Add formaldehyde (4% solution) until the solution turns pink/orange g) Titrate with 0.1N EDTA to a yellow end point. h) Concentration of Zinc g/l = mls EDTA X 1.3 *Formulation can be obtained on request Method 1b - Zinc Reagents 0.1N EDTA 12.5 % v/v HCL Xylenol Orange indicator ph 5.5 buffer solution a) Take a 5ml sample of solution and dilute to 50 ml with water b) Add 5 ml of 12.5% HCL. c) Add 20 ml of ph 5.5 buffer solution and the XO indicator. d) Titrate with 0.1N EDTA, colour changes from red to a yellow / orange. e) Concentration of Zinc g/l = mls EDTA X 1.3

18 Enviralloy Ni /07/2005 Page 18 Method 1c - Caustic Reagents N HCL Indigo-carmine indicator a) Take a 5ml sample of solution and dilute to 50 ml with water b) Add Indigo-carmine indicator. c) Titrate with N HCL, colour changes from orange to blue. d) Concentration of caustic soda = mls HCL X 8.0 2) Nickel - Nickel can either be determined by AAS or by the method below. Method 2a Reagents 12.5 % v/v HCL ph 5.5 buffer solution 20% ammonia citrate 5% gum Arabic 0.5% Nioxime a) Accurately pipette 10 mls of plating solution into a 100 mls volumetric flask. Make up to the mark with water. b) Pipette 2 ml of this dilution into a beaker and add 2 mls of 20% ammonia citrate solution. c) To this solution add 5ml of 12.5% HCL and 20 ml of ph 5.5 buffer solution. Confirm that the ph is between 4 and 6. Add a few drops of EDTA indicator solution. d) Add 2 ml of the gum Arabic solution, then add 2 ml of the 0.5% Nioxime solution and dilute to 100 mls with water. Stand for 15 minutes. e) Measure 520 nm absorbance with UV/VIS spectrophotometer. f) Determine gm of nickel using standard nickel curve.

19 Enviralloy Ni /07/2005 Page 19 Organic Additive Content The effectiveness of the organic components in the plating bath is best determined by Hull Cell testing. A stabilised power supply capable of delivering up to 2A is required for this testing. Hull Cell method It is important to use the same solution temperature during Hull Cell evaluation to ensure consistent results and subsequent interpretation. Good panels will be essentially free of defects and of good deposit thickness and even alloy distribution (see below). Thickness measurements are taken at points A-C on the panel and these correspond to current densities of 4, 2 and 0.5 Adm -2 respectively for a 1A panel. The measurements of deposit thickness and nickel content for each respective panel should be within the ranges given below. 1A 20min This Hull cell will give an indication of the general performance of the plating bath. Solution temperature at 24 o C Hull Cell 1A 20min Zinc / nickel conc. Optimum Temperature 24 o C A:C ratio 3 to 5:1 Thickness test A B C x x x um Ni 12-15% 12-15% 12-14%

20 Enviralloy Ni /07/2005 Page 20 Troubleshooting To ensure optimum performance of the Enviralloy Ni process it is essential to adhere to the following checklist. 1) Ensure good pre-treatment 2) Analyse the plating solution regularly 3) Maintain the zinc, nickel, sodium hydroxide and Replenisher 4) concentrations within the recommended limits 5) Maintain additives (where applicable) on an ampere hour basis 6) Control temperature of plating solution within the recommended 7) limits 8) Ensure good electrical contacts 9) Ensure good rack and plant maintenance If operational difficulties arise hull cell testing is a useful tool in solving solution problems. Details are given below of the more common type of faults encountered in alkaline zinc-nickel baths and how to correct them. Dull deposit appearance 1) Poor pre-treatment or oxidation/passivity of steel prior to plating. 2) Zinc and / or nickel concentrations outside the recommended limits. Low nickel content may cause burning and grey streaks in mid CD range. 3) Solution temperature too high. This will cause dull deposits in the low current density area particularly. 4) Applied cathode current density too low. 5) Replenisher concentration too low. This commonly results in faint dull streaks in the mid current density on a 1A panel. An addition of 1ml/l (0.1%) of Replenisher is generally sufficient to correct this problem. 6) Brightener concentration too low. This may cause burning/dullness in the high CD range. 7) Poor electrical contacts or poor rack design. It is essential that good rack design and positive electrical contacts be maintained.

21 Enviralloy Ni /07/2005 Page 21 Low nickel in alloy 1) Zinc and / or nickel concentrations outside the recommended limits. 2) Low level of Part A and / or B. Determine by Hull Cell whether an addition of either Parts A or B restore the correct percentage nickel in the deposit. 3) Low temperature. 4) Low level of Brightener. Determine by Hull Cell whether an addition of Brightener will restore the correct percentage nickel in the deposit. Pitting 1) Lack of wetter. This is normally coupled with unacceptable levels of caustic spray. An addition of up to 1ml/l should be sufficient to eliminate this problem. If excessive amounts of wetter are being added to the tank it is likely that oil is being dragged into the plating solution. The source of the oil contamination should be identified and removed. 2) Low Nickel in solution can cause burning and pitting effects in the deposit. This can be observed on a 1A Hull cell, particularly in the high current density areas. Burning or nodulation 1) High zinc metal concentration. This can lead to high current density deposit burning. The zinc nickel concentration should be restored to within recommended levels to eliminate this problem. 2) Low temperature. Temperatures below 20 o C (68 F) are not advised and can cause adhesion problems as well as burning. 3) Low concentration of Part D. This can be observed by Hull cell testing. It will result in excess deposit thickness of zinc in the high current density areas of the panel. An addition of up to 5ml/l in 1ml/lt increments, (0.1%) of brightener should be sufficient to correct the problem. 4) Applied current density too high. Measure the surface area of components and adjust current density within range specified in the TDS.

22 Enviralloy Ni /07/2005 Page 22 5) High carbonate levels. Increasing concentrations of sodium carbonate cause high current density burning. Ultimately, a low temperature treatment or a dilution of the solution will be necessary. 6) Zinc anodes in plating tank. Burning can occur if zinc dissolution is carried out in the plating tank and the cages come in contact with the anode rail or anode plates. 7) Low nickel concentration in the bath. Adjust to within recommended range. 8) Chloride contamination. If level has risen above 4 g/l then a either a dilution or replacement of the solution should be considered Poor adhesion 1) Poor pre-treatment. Please refer to the section on pre-treatment. 2) Low solution temperature. This lowers the efficiency of zinc-nickel deposition and increases the tendency to burning. Slower initial propagation, which occurs at low temperature, can cause poor adhesion. 3) Current interruption. If the current has been very low or switched off and subsequently raised back to recommended plating current density poor adhesion or lamination will occur within the deposit. 4) Chloride contamination. If the level has risen above 4 g/l then a either a dilution or replacement of the solution should be considered Low plating rate 1) Low metal concentration. As the zinc concentration is reduced from optimum, the plating efficiency decreases. It is important to maintain the correct zinc metal content of the bath (and of course the Zn:Ni ratio) to obtain optimum performance. 2) Low temperature. As mentioned above efficiency reduces as temperature is lowered. 3) Overdose. An overdose of Part A,B,D or Replenisher in the solution will reduce plating efficiency. Reducing additions of the particular additive by 50 to 100% until the plating rate is restored will correct this problem. 4) High carbonate. As sodium carbonate builds up in the solution to above 75g/l (10 oz/gall) plating efficiency reduces gradually. Periodic low temperature treatments to remove carbonate are advisable.

23 Enviralloy Ni /07/2005 Page 23 Zinc Generator System It is recommended that the zinc concentration in the Enviralloy Ni system be maintained by use of a zinc generator. A zinc generator consists of a steel tank (some 10 20% volume of the plating solution) in which steel cages containing balls (or domes) are suspended. The zinc generator greatly simplifies control of the zinc metal concentration and makes maintenance of the anode material easier. The generator tank must be constructed of mild steel. A suitable arrangement is described below, although different variations are possible depending on individual circumstances. Typical Layout Diagram Ideally, the plating solution is gravity fed to the generator via an overflow on the plating tank. It flows through the generator, which contains zinc balls held within mild steel cages. It is recommended that the steel cages are not descaled before immersion into the solution, as the presence of iron oxide promotes the dissolution of zinc metal. The solution is then pumped back to the process tank via a filter. The filter is located on the return side of the generator in order to filter out any large particles of un-dissolved zinc. An overflow tank is incorporated into the system to allow drainage of the generator during shutdown periods or when the concentration of zinc metal has become too high.

24 Enviralloy Ni /07/2005 Page 24 Many methods have been tried to maintain a consistent dissolution rate of the zinc in the generator tank. Most focus on changing the area of zinc in contact with the circulating electrolyte. Cages containing the zinc domes, fixed on a pulley that can be lowered or raised and valves to control the solution level are the most popular. However, for simplicity manually adjusting the zinc dome volumes is the most common approach. Insoluble Anodes Insoluble anodes used in the plating tank should be made of pure nickel. Nickel sheet is ideal for this. Nickel plated steel can be used (min. 25um Ni), but will degrade quicker than pure nickel and can give inferior deposit throwing power. Bolting them to submersed nickel or nickel plated steel (i.e. not copper) anode rails is recommended to make the best electrical contact. Suitable dimensions for the nickel anodes could be mm (6 10 ) wide, the depth will depend on the components being processed. Zinc anodes in the process tank are not recommended because: They can polarise at current densities above 1.5 Adm-2 (15 Aft-2). They can cause roughness in the plating solution. Control of the zinc metal concentration is more difficult Zinc Generator Volume It is not possible to predict the exact dissolution rate of zinc-nickel metal in the Enviralloy Ni solutions. This is because many factors influence the rate at which the zinc metal dissolves. These factors include; the concentration of sodium hydroxide, complexant, temperature, zinc to steel cage area ratio, plant loading, solution flow and agitation etc. The major factor when estimating zinc generator size is the plant loading. Experience has shown that generator volumes are usually between 10 20% of that of the plating solution, the larger percentage values being used for barrel installations. As the Enviralloy Ni operates at approximately 60% cathode efficiency, 0.7 kgs (1.6 lb) of zinc will need to be generated for each 1,000 Ah passed. The Enviralloy Ni process has been proven to be more efficient than other alkaline zinc-nickel plating systems. The cathode efficiency will have a direct impact on the ability of any existing generator to maintain a stable zinc concentration. Therefore, we recommend that the zinc generator is evaluated as part of a plant audit, to ensure that there is sufficient capacity to increase the dissolution of metal.

25 Enviralloy Ni /07/2005 Page Passivation Systems & Top Coats Feature Deposit contains between 12-15% nickel Process developed for use with TriPass passivation systems Even passivation films Benefit Accepts both hexavalent and trivalent passivates Ideally suited to meet new End of Life Vehicle (ELV) directives Improved corrosion protection The purpose of conversion coatings is simply to protect zinc-nickel deposits from corrosion. Environments likely to produce conditions where corrosion can be accelerated include air and sea shipping, long-term storage in humid environments and severe environments like coastal regions. Conversion coatings increase the resistance of zinc-nickel and plated coatings against these types of corrosion, thus considerably extending component life. Traditionally, conversion coatings were based on hexavalent chromium compounds. However, new legislation and corporate policies are beginning to restrict use of hexavalent chrome compounds due to toxicity and difficulty in recycling. The primary driver for hexavalent chrome is the EEC legislation End of Life Vehicle directive (or ELV). In order to passivate zinc-nickel deposits with systems free of hexavalent chrome compounds, the alloy must contain a minimum of 12% nickel. The Enviralloy Ni will give a consistent alloy distribution at or above this percentage and therefore are ideal for trivalent passivation. These new light iridescent TriPass coatings give conversion coatings whose performance can exceed the protection offered by traditional hexavalent films and are exceptionally resistant to thermal shock treatment.

26 Enviralloy Ni /07/2005 Page 26 Enviralloy Ni has been developed to work synergistically with the MacDermid trivalent TriPass processes to give high anti-corrosion performance coatings without the use of hexavalent based compounds. Film type Passivate Type Corrosion Resistance MacDermid Passivate Blue/Grey Trivalent Up to 200 TriPass ELV 3000 Iridescent Trivalent > 200 TriPass ELV 2000 Black Trivalent > 200 TriBlack Yellow Hexavalent > 200 Iridite 880 Black Hexavalent > 200 Iridite 990 *Time to white rust for rack passivated work. Spec. ASTM B117, no thermal shock treatment A suitable trivalent passivation sequence for the plated zinc-nickel coating from the Enviralloy Ni process would be as follows: 1) Zinc-nickel plate minimum 5 microns 2) Rinse X 2 3) Passivation 4) Rinse X 2 5) Topcoat (optional) 6) Oven dry (< 70 o C) A suitable sequence for the TriBlack process over a zinc-nickel coating from the Enviralloy Ni process would be as follows: 1) Zinc-nickel plate minimum of 8um 2) Rinse X 2 3) Activate in 0.5% Hydrochloric acid 4) Rinse 5) 1 st dip - TriBlack, seconds 6) Drain off or centrifuge (1 2 minutes) 7) Cure 5 10 minutes at C 8) 2 nd dip - TriBlack, seconds 9) Drain off or centrifuge (1 2 minutes) 10) Final cure 10 minutes at C

27 Enviralloy Ni /07/2005 Page 27 A suitable hexavalent passivation sequence for the plated zinc-nickel coating from the Enviralloy Ni process would be as follows: 1) Zinc-nickel plate minimum 5 microns 2) Rinse X 2 3) Passivation 4) Rinse X 2 5) Fixer solution 6) Rinse and Topcoat (optional step) 7) Oven dry (< 70 o C) Enviralloy Ni produces a uniform zinc-nickel deposit, which is easy to passivate. Using the correct passivate to meet a given standard, the Enviralloy Ni process can give improved resistance to red rust over competitor processes, particularly on complex and difficult to plate components. The following guide highlights the MacDermid preferred range of passivates and topcoats. Trivalent based passivation systems Where high corrosion performance is required from a trivalent passivate, TriPass ELV 2000 or 3000 are recommended. The achievable corrosion performance is similar to traditional yellow hexavalent passivates before any thermal shock is applied. However, the protection obtained after thermal shock is superior to hexavalent systems making it suitable for use in environments where high temperatures are regularly encountered (i.e. engine compartments / brake callipers). These processes are simple to make up and operate and can be used in both rack and barrel applications. TriPass ELV 2000 TriPass ELV 3000 Colour Iridescent Blue / grey Concentration ml/l 100 ml/l ph Temperature C C Immersion Time sec secs

28 Enviralloy Ni /07/2005 Page 28 During use the concentration of the TriPass solution will decrease and the ph will increase. The passivate is maintained by regular additions of the applicable TriPass concentrate. Accurate control of the ph is essential to ensure the process operates successfully. The ph should be maintained by additions of concentrated nitric acid. The nitric acid and TriPass concentrate can be pre-mixed for auto dosing purposes. Suitable additions could be per 100 m 2 of treated surface area: TriPass ELV % nitric acid To maintain ph TriPass ELV litres TriPass ELV % nitric acid litres TriPass litres Trivalent Black System (Dip-Spin) Where a high corrosion resistant black coating is required from a trivalent passivate, TriBlack is recommended. This process is an all-in-one black trivalent passivation and sealant process. The TriBlack solution contains no hexavalent chromium compounds and is therefore suitable to meet the new End of Life Vehicle directives. The passivated film contains a unique mixture of inorganic and organic compounds which provides exceptional corrosion protection. The film also incorporates an integral lubricant which is designed to meet specifications requiring coefficient of friction properties between This material should always be tested under the conditions for which it is intended. TriBlack Part A 500 ml/l TriBlack Part B 150 ml/l DI water to 1 litre Immersion time seconds Temperature C Curing schedule 5 10 minutes at C (metal temperature)

29 Enviralloy Ni /07/2005 Page 29 TriBlack Application By Dip Spin In order to get good even colouration and full coverage it is important to control application conditions. TriBlack is usually used at a concentration of % concentration of part A. The working tank should be maintained at degrees C in normal operation. The higher the concentration used the thicker the final layer will be. For large scale production where there is more tendency for items to have restricted drainage during spinning it is normal to use a concentration level of 50 %. The TriBlack concentration should be maintained at the same level from day to day. This can be done by maintaining the working level of TriBlack with TriBlack A &B at the initial makeup concentration. This concentration can then be checked periodically by measuring total solids or chromium content by the methods provided. Bathside viscosity checks using a B2 flowcup can also be useful to give a quick rough check on concentration. After dipping excess TriBlack is then spun off in the basket. Due to the effects of centrifugal force a large diameter basket should be spun at a lower speed than a small basket to achieve the same effect. As a general guideline a spin speed of 200 linear metres is recommended. To avoid unnecessary damage during this process a slow ramp up to final speed of seconds can be used. A spin time at final speed of seconds is normally sufficient and for larger loads it is common to use a forward and reverse step to make sure that excesses are removed from the centre of the load. The basket is approximately half filled for the process. Overfilling makes it difficult to avoid thread fill and sticking together whilst very low loadings lead to low coating thickness and unnecessary damage. Generally it will be found that some parts have a greater tendency to trap excess coating than others so it may be necessary to vary the above parameters occasionally to maintain good results. To maintain the required corrosion resistance and cosmetic finish a double coating will normally be required.

30 Enviralloy Ni /07/2005 Page 30 TriBlack Troubleshooting Guide Problem Grey or patchy black finish Too thick, drips or thread fill Work sticks together Possible causes Basket underfilled Spin speed too fast Low TriBlack concentration Spin speed too slow Basket overfilled High TriBlack concentration Basket overfilled Extra spinning or reverse step needed High TriBlack concentration Hexavalent Passivation Systems Where high corrosion performance is required from a hexavalent passivate (chromate), Iridite 880 or 990 are recommended. These processes are simple to make up and operate and can be used in both rack and barrel applications. They have been developed to work synergistically with the Enviralloy Ni system. After passivation, either a fixer or suitable topcoat is advisable (or both). Iridite 880 Iridite 990 Colour Iridescent Black Concentration Part A g/l ml/l Concentration Part B ml/l ph Temperature C C Immersion Time sec secs Chrome content in passivates In order to determine the level of total chromium contained within a passivation film, the deposit and passivate layer are stripped in dilute mineral acid and the total chromium concentration is measured by Atomic Absorption. In order to ascertain the chromate level a second technique, X-ray Photoelectron Spectroscopy* (XPS), is employed. This method allows the ratio of Cr(III) to Cr(VI) in a passivate film to be estimated.

31 Enviralloy Ni /07/2005 Page 31 Comparison of chromium concentrations using chemical analysis method Type of passivate Thickness in nm Total Cr* mg/m -2 Yellow Black Peak fit data showing Cr(III) concentrations relative to Cr(VI) based on XPS spectra of various passivate films. Passivate Film Cr(III) as Cr(OH)3 Cr(III) as Cr2O3 Cr(VI) Yellow 23% 36% 41% Black 55% 22% 22% The above results show that there is both hexavalent and trivalent chromium species present in hexavalent chromium based passivates. The amounts / ratios will vary depending on the type of passivate used, the proprietary process employed and the operating parameters utilised. Also the methods for the detection used (for these compounds) do have limitations and are therefore recommended for qualitative analysis only. The concentration of chromium within a passivation film is also dependent on immersion time, solution concentration, ph, and temperature and contamination levels. Therefore, the above table should be used as a reference guide only. * Ref: Lionel Thiery, Galvanotechnik, page 3373.

32 Enviralloy Ni /07/2005 Page 32 Chrome (VI) content in trivalent based passivates It is recognised that under certain conditions trivalent passivation films can generate or contain small amounts of hexavalent chromium. These levels are at the limits of detection with current analytical equipment and are orders of magnitude lower than any traditional hexavalent chromate film. Typical Hexavalent Chrome Content of Trivalent passivate films Total Cr content mg/m2 Leachable Cr(VI) mg/m -2 % Leachable Cr(VI) to total Cr Iridescent type < % Blue type < % GMW-3034 General Motors have recognised the need to eliminate hexavalent chromium and have issued specification GMW-3034 as a method of detecting its presence in passivate films. This specification details the dissolution of the passivate film and the detection of any residual hexavalent chrome compounds using 1,5-diphenyl carbizide. 1,5-diphenyl carbizide produces a red coloured complex in the presence Cr (VI) compounds. These can then be measured by UV/vis spectroscopy. This specification is a go / no-go test with the maximum allowable limit of hexavalent chrome compounds at 0.1 mg/m -2 of passivated area. GMW-3034 test on the Trivalent based passivates Deposit Hexavalent Yellow Peroxide based trivalent Iridescent GMW-3034 Standard Trivalent (TriPass ELV 2000, 3000) Pass or Fail Fail Fail Comparative standard Pass

33 Enviralloy Ni /07/2005 Page 33 Relationship between Passivation Colour, Type and Alloy Content Due to the variation in nickel content of zinc-nickel deposit, passivation processes may produce variable results in terms of film formation, thickness, colour and corrosion performance. It is therefore important to establish the correct operating conditions for alloy composition and passivation process to ensure consistent performance results. The graphic details below show how the alloy content of Enviralloy Ni should be controlled in order to obtain the desired passivation colour. Iridite Hexavalent Passivates TriPass Trivalent Passivates Work within the following ranges for specific colours: Hexavalent Yellow Passivation up to 13% nickel Hexavlent Black Passivation over 13% nickel Clear Trivalent Passivation up to 12.5% nickel Iridescent Trivalent Passivation over 12.5% nickel Black Trivalent Coating Any nickel content using TriBlack (dip-spin) The most cosmetically attractive clear finish can be obtained by using TriPass ELV 2000 under the following conditions. Make Up 10% v/v Temperature oc ph Immersion seconds Shorter immersion times are better for higher alloy contents.

34 Enviralloy Ni /07/2005 Page 34 Topcoats & Seals Although it has long been recognised that conversion coatings on sacrificial deposits increase their performance considerably, today s coating specifications often require performance levels which exceed the limits of the conversion coatings detailed above. The principal improvements required by these ever more demanding specifications are: Better corrosion protection (usually defined as improved resistance to Neutral Salt Spray, ASTM B117 or by cyclic corrosion methods) Improved resistance to thermal shock test Specific torque and tension requirements Improved contact corrosion performance Improving coating aesthetics In order to achieve the various criteria outlined above with minimal cost increase, topcoats (or final finishes) are now commonly applied to passivated coatings. These can be inorganic, organic or a mixture of both (organo-mineral). The majority of these topcoats are aqueous solutions applied by single stage dips incorporated into conventional electroplating lines or as the final stage in mechanical plating.

35 Enviralloy Ni /07/2005 Page 35 Torque and Tension Control The use of torque (turning or twisting force) has long been associated with methods of tightening and inspecting bolts. The object of tightening bolts is to achieve a minimum tension (straight pull), not torque, in the bolts. As a nut and bolt are tightened the components to be fastened are clamped together. The thread angle in the bolt converts the force applied into tension (or stretch) in the bolt shank. The amount of the tension created in the bolt is critical, because when a bolt is tensioned correctly it is working at its optimum efficiency and will resist coming undone. However, if the tension is too low the nut could vibrate or work loose. If the tension is too high (over-stretched), the bolt could break. Therefore, it is important to have these figures available so that the end product will be safe, efficient and economical. There is a relationship between torque and tension, but it is highly variable and must be used with caution. The variables in the torque-tension relationship include lubrication, thread fit, the use of a washer and the tension in the bolt. The torque used to tighten a bolt is consumed by overcoming the friction between nut and washer (about 60%), overcoming the friction between bolt thread and nut threads (about 30%), and providing energy to elongate the bolt (about 10%). Tests have indicated that torque-tension relationships for structural bolts easily vary by as much as 40%. Specifications do not permit the use of any tabulated torque or calculated torque for either installation or inspection. Installation and inspection torque s must be determined or set using Skidmore-Wilhelm (or similar) devices to establish actual tension, then determine the torque. A basic equation to estimate the torque-tension relationship is: T = x P x D Where T = torque (foot-pounds) P = bolt tension (pounds) D = bolt diameter (inches) The value of , called the nut factor, is a traditional industry average. It can range as low as 0.01 for well-lubricated assemblies and can exceed for dry or rusty fasteners.

36 Enviralloy Ni /07/2005 Page 36 Torque Tension relationships of zinc-nickel plated fasteners Zinc-nickel alloy plated deposits generally exhibit unpredictable torque/tension relationships. Furthermore, zinc-nickel deposits have a significantly higher coefficient of friction than either zinc or other zinc based alloys. This means that applying conventional post plating lubricants will give a higher CoE than expected. Also the CoE spread or range is usually wider than anticipated. Friction control lubricants should therefore be chosen and tested carefully when zinc-nickel is specified. In order to give predictable relationships MacDermid recommend the following lubricant types: Lubricant suspension - i.e. Torque n Tension control fluids Organic Coating with lubricant Suspension - i.e. Maculube 9775 Torque n Tension Control Fluids Torque n Tension Control Fluid MPE 1186 is formulated to apply a dry lubricating film to machined parts, especially threaded fasteners which have been protected from corrosion by sacrificial or barrier coatings like zinc-nickel electroplating. The objective of this lubricant is to decrease the coefficient of friction of coated parts and to control the induced tension obtained with a given tightening torque. Torque n Tension Control Fluids 11 or 15 will also increase the corrosion protection of a plated layer. These products are generally applied off line using dip-spin or curtain wash process equipment. Application of Torque n Tension Control Fluids requires the parts to be free of oils. Torque n Tension Control Fluid / UV Fluid can be used as received or diluted with water. Torque n Tension Control Fluids 11 or 15 are generally used as received. The concentration that is required will depend on several factors, the quantitative importance of which cannot be determined in advance for each individual application.

37 Enviralloy Ni /07/2005 Page 37 The following methods of application can be used: 1) Dipping parts in solution using perforated or screened baskets then drying on a belt or spin dryer. 2) Cascade or Curtain Coater in which the parts pass through a running cascade of lubricant on a belt or conveyor then on to a drying stage. 3) Spraying the solution on the parts in liberal volumes using equipment such as a parts or dunk washer, then drying.