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EN Process Performance: Effect of Agitation, Loading and Stabilizer Level

EN Process Performance: Effect of Agitation, Loading and Stabilizer Level. By Matthew J. Sisti and Jean LaPlante. Presentation Outline. Brief introduction and process review Experimental objectives Experimental procedures Results Conclusions/Recommendations.

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EN Process Performance: Effect of Agitation, Loading and Stabilizer Level

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  1. EN Process Performance:Effect of Agitation, Loading and Stabilizer Level By Matthew J. Sisti and Jean LaPlante

  2. Presentation Outline • Brief introduction and process review • Experimental objectives • Experimental procedures • Results • Conclusions/Recommendations

  3. Brief Introduction & Process Review • Early formulations had many shortcomings • Turbidity, instability, short solution life as well as poor deposit characteristics were commonplace • Commercial success of EN led to technological advancements

  4. Brief Introduction & Process Review (cont.) • Contemporary EN formulations: • are easy to make up and operate. • are typically consistent from lot to lot. • offer many process and deposit benefits • are available in “all shapes and sizes” • still suffer from a number of technical flaws!

  5. Periodic problems with currentEN technology (the 6 P’s) • Poor corrosion resistance due to high deposit porosity. • Inferior deposit passivity resulting in poor chemical resistance and staining. • Pitting of thick deposits • Edge pullback and related phenomena • Slow plating rates • Moderate to high plate-out

  6. Balance • EN is a process in a perpetual state of conflict • High purity solution yields highest quality deposit. • Impractical in terms of process performance:Not User-Friendly Must find balance between optimum deposit and process performance.

  7. Presentation Outline • Brief introduction and process review • Experimental objectives • Experimental Procedures • Results • Conclusions/Recommendations

  8. Experimental Objectives Can we modify an EN process to maximize performance? • deposit porosity • deposit passivity • pitting • edge pullback • slow plating rates • plate-out

  9. Deposit porosity • EN is cathodic to the substrate in more than 75% of current applications. • Corrosion of the anode (substrate) occurs through deposit porosity. • Porosity can be reduced through pretreatment and EN chemistry. • Current study will evaluate porosity reduction through modified solution operation.

  10. Deposit passivity • Passivity relates to a more “impervious” condition of a particular metal or alloy. • Indirect measurement of deposit purity and phosphorus content. • Co-deposition of impurities reduces passivity. • RCA nitric acid test was used to compare “passivity” of deposits plated under different conditions.

  11. Deposit pitting • Thicker deposits (>1.0 mil) are more susceptible. • Medium phosphorus processes produce more pitting. • HPEN has 1/4 of HM stabilizer • HPEN plates 1/2 speed • Deposit pitting of a HPEN process under various conditions were evaluated.

  12. Edge pullback • Typically caused by high concentrations of HM stabilizers, brighteners and/or metallic contaminants. • Co-deposition is governed by diffusion • Higher concentrations of stabilizers adsorb in areas of high solution velocity (i.e edges) • Effect of loading, agitation and stabilizer level on edge effect phenomena will be evaluated.

  13. Plating rate • Critical process characteristic • Function of: • Temperature • pH • Solution age • Chemistry type, exaltants, hypophosphite level • Our study focused on the effect of : • Stabilizer type and level • Agitation • Workload to solution volume on plating rate

  14. Plate out/solution stability • Many factors play a role in process stability • Solution chemistry • Operating parameters (pH, Temp., Conc.) • Equipment and maintenance • Our study focused on the effect of : • Stabilizer type and level • Agitation • Workload to solution volume on solution stability

  15. Presentation Outline • Brief introduction and process review • Experimental objectives • Experimental Procedures • Results • Conclusions/Recommendations

  16. Experimental Procedures • Pertinent data can be found in the Conference Proceedings • Critical notes • All solutions tested were high phosphorus • All EN solutions were aged to 0.5 mto’s • Substrates were 1010 mild steel panels and 1”x 1/4” sheet metal screws.

  17. Experimental Procedures (cont.) • Testing • Porosity • Ferroxyl per ASTM B733 of 1” bolts plated to 0.4 mils. • Pitting • Panels plated to 2.0 mils and examined at 20x. • Passivity • Panels plated to 0.2 mils, dried and immersed in concentrated nitric acid. • Time to black edges as well as entire panel.

  18. Experimental Procedures (cont.) • Testing • Plate-out/instability • Palladium stability • Evidence of plate-out • Cleaning cycle • Conventional cycle for low carbon steel with two electrocleaning and acid activation steps.

  19. Test Standardization • Solution pH: 4.8 Temperature (F): 190 Agitation: moderate • Loading: 0.4 ft2/gal Stabilizer level (ppm): varied

  20. Presentation Outline • Brief introduction and process review • Experimental objectives • Experimental Procedures • Results • Conclusions/Recommendations

  21. Effect of Solution Age

  22. Effect of Stabilizer Level • Solution pH: 4.8 Temperature (F): 190 Agitation: moderate • Loading: 0.4 ft2/gal Stabilizer level (ppm) variable

  23. Ferroxyl Porosity Test for 0.4 mil HPEN - 0.1 ppm HM Stabilizer

  24. Ferroxyl Porosity Test for 0.4 mil HPEN - 1.0 ppm HM Stabilizer

  25. Porosity of 0.4 mil HPEN deposit vs Heavy Metal Stabilizer Level 0.1 ppm 0.3 ppm 0.6 ppm 1.0 ppm

  26. Effect of Solution Loading • Solution pH: 4.8 Temperature (F): 190 Agitation: moderate • Loading: variable Stabilizer level (ppm) 0.3

  27. Effect of Agitation • Solution pH: 4.8 Temperature (F): 190 Agitation: variable • Loading: 0.4 ft2/gal Stabilizer level (ppm) 0.3

  28. Results (cont.)- Synergy • Results thus far are for experiments with only one operating parameter varied. • Real world operation of an EN process is not so static. • Optimized performance requires combination of ideal conditions.

  29. Synergy • The final group of 120+ experiments were run holding one parameter constant while all others were varied. • The results were tabulated, sorted and trends recorded.

  30. Analysis of Synergy Data • Due to volume of data, averages of testing results were utilized. • Simplified analysis procedure and eased trend recognition. • Sorted porosity and pitting data can be found in the proceedings.

  31. HM Stabilizer level vs Deposit Porosity and Pitting

  32. Solution Loading vs Deposit Porosity and Pitting

  33. Agitation vs Deposit Porosity and Pitting

  34. Presentation Outline • Brief introduction and process review • Experimental objectives • Experimental Procedures • Results • Conclusions/Recommendations

  35. Conclusions • Effect of solution age: Deposit porosity increases Deposit pitting appeared unrelated (to 5 mto) • Effect of heavy metal stabilizer: Higher levels promote porosity and pitting Plating rate independent Higher levels reduced passivity Higher levels increased stability More pronounced edge effect phenomena

  36. Conclusions • Effect of workload to solution volume: • Higher loading reduced deposit pitting and increased deposit passivity. • Plating rate was independent of loading. • Effect of solution agitation: • Pitting reduced with moderate air/nitrogen. • High rotational agitation increased pitting and reduced passivity • Deposit porosity increased with agitation • High rotational or air agitation increased speed • Solution stability increased with agitation • No benefits from nitrogen were realized

  37. Suggestions • Pay close attention to solution loading. • Underloaded solutions should be run below 85% activity and agitation reduced. Monitor stability. • For heavy build applications-run at 85% activity or below and utilize air agitation.

  38. Suggestions • To increase stability • Maintain chemistry at or near 100% • Increase solution movement (add air) • To eliminate edge effect phenomena • Maintain chemistry at or below 85% • Reduce agitation • Increase workload • Monitor concentrate age

  39. Suggestions • To improve corrosion protection • Maintain chemistry at or below 85% • Reduce agitation • To increase passivity • Maintain chemistry at or below 85% • Increase workload • Maintain plating speed below 0.5 mils/hr

  40. Finally.......... • Work with your supplier. • Ask for type or class of stabilizer and target level • Ask about designer EN • Key to success is balance between deposit and process performance

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