How to Avoid Premature Coating Failures

1. How to Avoid Premature Coating Failures Proper Removal of Soluble Salts After Detecting Their Presence CSI Webinar 10/19/10 Presenter: Regis DoucetteChlor*Rid Intnl., Inc.(201) 664-5487Regis@chlor-rid.com

2. Awareness • Recognition • Elimination Coating project costs: 80/20 rule applies 80% Surface Preparation 20% Coating Objective: Reduce liability of premature coating failure from corrosion with better knowledge and field-tested specification details Goal: Achieve full life cycle coating performance

3. Why salts are a big issue? • Lead based coatings are banned. • Lead formed insoluble salts. • Visual standards are insufficient. • Salts are nonvisible. • Specifications may not adequately address nonvisible contaminants. • Residual salts are a leading cause of premature coating failure. • Testing and removal is always much less than the cost of premature failure. Salts are a controllable variable!

4. Uhlig and Revie’sCorrosion & Corrosion Control:“The most important single factorinfluencing the life of a paint isthe proper preparation of the metal surface” H. Mitschke’s award winning 2001 JPCL article: A 1µg/cm2 increase in chlorides has the potential to reduce coating life by 50%.

5. Reality Check • “Prior to 1995, it is estimated that at least 3 out of 4 contractors suffered major failures during projects or shortly thereafter. Most coatings did not survive more than 5 to 7 years. Now with changes, including (soluble salt remover), we have an approximately 70 to 90% reduction in lifecycle costs, have reduced premature coating failures and increased service life.” Non vendor specific edit

6. What are Soluble Salts? • Ionic contaminants • Water soluble inorganic compounds • Primarily chlorides, sulfates, and nitrates • Non-visible contaminants • Can bond electrochemically to the metal substrate

7. Sources • Marine environments (sea water-chlorides) • Abrasives (chlorides/sulfates) • De-icing salts (chlorides) • Environmental fallout & acid rain (sulfates/nitrates): • Stack gases • Auto/vehicle emissions • Chemical processes/plants & power plants (many combinations of salts) • Water and sewage treatment facilities • Lightning

8. Values X 10 = µg/cm2 deposited per yr.

9. Values X 10 = µg/cm2 deposited per yr.

10. Values X 10 = µg/cm2 deposited per yr.

11. Sulfuric Acid Reigns Supreme http://www.turi.org/library/turi_publications/massachusetts_chemical_fact_sheets

12. Values X 10 = µg/cm2 deposited per yr.

13. Nitrates Sulfates Chlorides

14. Non-visible • Visually clean substrates are not adequate • Soluble salts require testing to be detected • Which salt is the problem? - Primarily dependent on service environment

17. Microgram per square centimeter • Pinky fingerprint approximates 1 square centimeter • M&M candy sliced into one million pieces •     --single slice = 1 microgram • Salt packet from McDonalds for fries •     --disolved in water • --then spread over 1,000 sq ft would deposit • 1 microgram per square centimeter • µg/cm2

18. Relative Size Chart 40 mil

19. Perspective -- Sizing Hair Beach Sand

20. Detrimental Effects of Salts • Interferes with adhesion • Accelerates corrosion • Causes blistering of coatings

21. Corrosion Cell • A corrosion cell consists of 4 components • An anode ( “-” provided by steel itself) • A cathode ( “+” provided by steel itself) • A metallic pathway (provided by steel itself) • An electrolyte (salt + moisture = electrolyte)

22. Coating failure Corrosion products Metallic pathway Cathode Anode Electrolyte

23. Electrolyte—the ONE and ONLY variable we can control is… • Salts are hygroscopic = Draw moisture • All liquid applied coatings are permeable and salts will draw moisture through the coating film, thereby providing the electrolyte needed for corrosion activity • Some coatings are less permeable than others

24. Osmotic Blisters • The same hygroscopic action which causes corrosion also causes osmotic blistering • The hygroscopic action of salts builds up pressure within a blister which can exceed the bond strength of the coating

26. A. B. A = Fingerprint effect B = Random test sample location would yield imperfect results

27. Salt Corrosion Cycle Iron +Salt + Moisture = RUST + Acid Fe + 2H+→ Fe+2 + H2↑ Fe+2 + O2 +4H+ → Fe+3 + 2H2O Fe+3 + 3Cl- → FeCl3 2FeCl3 + 3H2O → Fe2O3 + 6HCl Without remediation, repeat reaction cycle

28. Detecting Soluble Salts • Lab analysis • Time consuming and costly. • Field testing • Conductivity • Ion specific

29. Testing for Salts Two parts: • Extractions • Analysis

30. Detecting Soluble Salts • Extraction methods • Swabbing (DI water) [25 – 35%] • Patch Cell (DI water) [45 – 60%] • Wet filter paper (DI water) [??] • Magnetic cell (DI water) [45 – 60%] • Sleeve method (proprietary acid solution) [80%] • Boiling (lab; destructive field sample) [90 – 95%] • Quantitative analysis (Sources: SSPC TU4; Third party laboratories)

31. Analysis methods Two distinct methods: • Conductivity – measures all conductive constituents. • Ion specific – measures the specific ion of concern; chloride, sulfate, or nitrate.

32. Conductivity Method • Measures everything conductive in the sample. • Many species are not detrimental to the coating film nor induce premature coating failure. • Measures all minerals. • Conversion to chloride level is an estimate. • Assumes a lab correlation based on 100% chlorides. • Conductivity and reactivity are different.

33. A B C D E F G H I J K -- L M N O P Q R S

34. Conductivity vs Chloride Ion Specific19 panel tests with derived index for analysis

35. Plotted test points sorted by ascending values of Chloride Ion Specific results.

36. Sorted by ascending values of Conductivity results.

37. Ion specific method: • Measures the specific problematic ion. • Can measure different ions – chlorides, sulfates, and nitrates. • Reagent liquid chemicals can measure chlorides, but usually result in a range ( > to < ).

38. Ion specific method limitations: • Quantab strip: • Lot specific factor for calculation. • Does not read below 30 ppm; • 7.5 µg/cm2 equivalent with Bresle and 3 ml DI. • Reagent liquid chemicals can measure chlorides, but usually result in a range ( > to < ).

39. Chloride Analysis by Ion Detection Tubes • Sealed ampoule, break both ends and immerse in extract solution • Cl- read from calibrated tube in PPM and micrograms per square centimeter • ISO 8502-5

40. Analysis of Sulfate • Electronic turbidity method • Add barium chloride to extract solution to form BaSO4 • Measure absorbency/transmittance • New Field Test Kit • ISO 8502-11 • Maryland Bridge • I-95 Delaware • Casciano Bridge near Newark A/P

41. Analysis for Nitrates • Dip pillow end of nitrate strip into extracted solution for 2 seconds • Wait 1 minute and compare color on pillow to color on comparator card • NASA Gantry • St. Lawrence Seaway

42. Criteria for Chlorides: Units = µg/cm2 * Equivalents

43. Risk Levels for Soluble Salts:

44. Cumulative Risk • Threshholds for each, but risk additive & not independent nor mutually exclusive • How much weight should go on thin ice? Chlorides Sulfates Nitrates Sophie Chloe Nitree

45. Units for Soluble Salts • Surface Concentration: • Micrograms per square centimeter • Abbreviated (µg/cm2) • Solution Concentration: • PPM (parts per million) • Convert to µg/cm2 based on volume and area Note: 10 mg/m2 = 1 µg/cm2

46. Standards • SSPC Guide 15 • extraction procedures • analysis procedure • units, conversions • ISO • chloride ion, sulfate ion • conductivity • extraction

47. Removal

48. Bonding strength Why are salts left behind if they are water soluble? The electrochemical attachment of salts to the substrate (adsorption) are greater than the forces applied to remove them.

49. Surface Preparation Methods • Ultra High Pressure washing - Profile impact - Salt mitigation • Abrasive blasting & Pressure wash (3000 psi min) cycles with water. - Multiple passes. - Bonded salts. - Time and cost. • Wet abrasive blasting - Micronic particles. - Rinsing required. • Abrasive blast followed a soluble salt REMOVER wash. - Cost effective.