Innovations in Pretreatment: Advanced Non-Phosphate Pretreatments. Suresh Patel Chemetall

Transcription

1 Innovations in Pretreatment: Advanced Non-Phosphate Pretreatments Suresh Patel Chemetall

2 utline verview of Advanced Pretreatments (APs) What are Silanes? What are Phosphonates? Practical application Choosing the right pretreatment Successfully making the transition some practical lessons/case studies Final Comments

3 Advantages Environmentally friendly no zinc, no/low phosphorous Energy savings.operate at ambient temperature Less capital investment.fewer stages needed Smaller bath initial charge smaller tank used Simple, robust operation. Wide operating windows No scale Almost no sludge Simple waste treatment Versatile work with most substrates, paints Match paint performance of process replaced Advantage: Cost savings

4 Silanes Up Close

5 Silane Pretreatments What are they? rganic: rganofunctional silanes Inorganic: Unregulated metals such as zirconium How do they work? 1. Metals form ionic bond to substrate 2. Silane forms covalent bond to substrate 3. Silane cross-links

6 Silane Pretreatment rganic Plus Inorganic CH 2 H Si H Si Si Si CH CH 2 Si CH 2 H 2 CH 2 CH CH CH H Si Si Si H CH 2 Si Si Si H Si H CH 2 CH Si H CH 2 CH Si CH CH 2 CH 2 CH CH CH CH Si 2 Si Si Si H Si Si H CH 2 Si H H H H H H H Zr Zr Mn Zr Zr Zr Cu

7 What Does the Coating Look Like? Zinc Phosphate Silane 60 nm 6 μm SEM FEG-SEM Sample preparation: Induced crack initiation with liquid nitrogen

8 New Silane Developments High-performance applications Accelerator Unique silane molecules better e-coating on mixed metal better corrosion performance

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10 New Silane Developments Touch-Up, manual wipes For repair of spot defects Sand Defect Wipe on Silane Ready for Paint

11 New Phosphate-Free Developments Three-stage process Cleaner-coater Rinse Rinse Three-stage process Alkaline cleaner Rinse Silane coater Economical Good for more difficult soils

12 Phosphonates Up Close

13 Phosphonate Pretreatments What are they? rganic: Phosphonate Inorganic: Unregulated metals zirconium and titanium Proprietary activating ingredients How do they work? Covalent bonding of Phosphonate to substrate Ionic bonding of metals to substrate

14 Phosphonate Pretreatment rganic Plus Inorganic Ti R3 R2 P R1 Zr R3 R2 P R1 Substrate

15 Practical Application

16 Good Cleaning is Essential rganic soils (oils, metalworking fluids) Alkaline cleaning Inorganic soils (rust, scale, welds) Mechanical: grinding, blasting, etc. Pickling: acid followed by neutralization Advanced Pretreatments use less heat and weaker acids than phosphates, so they don t help with cleaning.

17 Good Rinsing is Essential Alkalinity Can precipitate active ingredients in AP Complexant from cleaner Complexes active ingredients in AP Phosphorous from cleaner False reading in phosphonate bath check Contaminants in general Can react with active ingredients in AP

18 How to Control the Rinses Conductivity limit: 200 μs/cm (150 ppm TDS) Automatic conductivity controller Exit fresh water halo Drip water conductivity

19 Product Selection 1) Washer considerations? Stainless Steel or Plastic Mild Steel Number of stages Rinsing 2) Water quality? DI or R Tap water 3) Phosphorous discharge limits? 4) Performance? Varies with paint Varies with substrate

20 Before Charging the Tank Plan, Action item list Baseline current process Write operating manual and log sheet Washer modifications Exit halos Counter-flows rder all titration supplies rder all automation equipment, feed pumps Chemically descale and rinse all stages Align nozzles

21 Converting a Typical 5-Stage Washer Cascades and halos cut water use in half Halo Halo Fresh Water Halo Clean Rinse Rinse Coat Rinse Waste Treatment Was Iron Phosphate Was Rinse (smaller)

22 Charging the Tank Post, read and understand MSDSs Use proper PPE Circulate water, then check conductivity Charge and adjust baths Retain bath samples and panel samples

23 Appearance on Cold Rolled Steel

24 Appearance on ther Substrates Steel Electrogalvanized Aluminum

25 Checking the bath Photometric methods Zirconium Titanium Phosphonate Silane ph Conductivity Free or Total Acid? Hach DR/890 Portable Colorimeter

26 Automation: Conductivity or ph Coating reaction and drag-out causes conductivity to fall ph to rise Sensor detects this change Pumps feed at assigned ratio Inorganic component rganic component Pulsatron Pumps

27 nce the Line is Running perator Training Verify performance Bath analysis in lab Coating weight Adhesion Corrosion testing Routine line audits UCL LCL Log SPC Data, Chart it, Post it May 1-Jun 3-Jun 5-Jun 7-Jun 9-Jun 11-Jun 13-Jun

28 A Transition Success Story When the winds of change blow, some people build walls and others build windmills.

29 The Situation, 2006 Utility vehicle manufacturer Nine-stage zinc phosphate process Two-step powder coat Chemical cost increases: phosphate, zinc, nickel Needs: Counter rising, chemical costs with other savings. More environmentally-friendly process for IS 14001

30 Actions Taken, Panels and small part tested Baseline established Cost savings calculated Decision to transition made Plan with timeline formulated Washer, counter-flows, exit risers re-plumbed Washer chemically descaled Line started-up perators trained

31 The Results, Salt spray results equal to zinc phosphate 30% reduction in water usage 90% reduction in sludge generation Environmentally-friendly process Stable process

32 Another Transition Success Story Do not be afraid of going slowly; be afraid of standing still.

33 The Situation, Prior to 2009 ff-road, snowmobile, motorcycle, military vehicle manufacturer Six-stage iron phosphate process E-Coat primer and powder topcoat Needs: Reduce overall pretreatment costs Reduce waste treatment costs Maintain excellent paint performance

34 Actions Taken, 2008 Panels tested Baseline established Cost savings calculated Decision to transition made Plan with timeline formulated Washer chemically descaled Line started-up perators trainedyesterday

35 The Results, $72,000 annual energy savings 40% savings in waste treatment sludge 35% savings in waste treatment cost 15% reduction in pretreatment cost overall Salt spray results equal to iron phosphate + seal Environmentally-friendly process Stable process with wide parameters

36 Some Real World Lessons

37 This never happened before Spots that bleed through the paint Cause: Drips from the conveyor loadbars

38 Meanwhile, at another facility Paint adhesion failure Cause: HRS mill scale was softened by acid pickle

39 Baseline Important to baseline thoroughly Paint performance Understand the whole process Changing from phosphate to non-phosphate didn t change Conveyor configuration Substrates, acid pickle, and etc.

40 Some Final Comments Communicate clearly, form a team, carefully plan with: Equipment supplier Pretreatment supplier Paint supplier Performance requirements Limitations Cost Substrates Water quality Paint Equipment Materials of construction Number of stages

41 Thank You Questions?