Improving Adhesion: Examining the Electrochemistry of Organic Inhibitors

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Elfreda Felicia Sharp
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1 Improving Adhesion: Examining the Electrochemistry of rganic Inhibitors

2 Benefits of rganics Chemisorb onto metallic substrates Complex with metal ions at substrate Neutralize & absorb the corrodents Decrease permeability (barrier enhancement) Anodic passivators Improve wetting Promote adhesion Plug pores (defects)

3 All Coatings Made Here

4 Periodic Trends In general, Electronegativity increases to the right and increases upwards Greater ability to attract electrons to itself Close proximity to associated elements yields a dynamic sharing relationship among electrons Surface treatments allow for metals to associate with select elements in a sharing relationship that might otherwise not exist

5 Relative Electronegativities

6 CRRSIN CELL DIAGRAM 3/2 2 Water Droplet Rust Fe 2 3. H 2 3 n H 2 2 Fe 2+ 2 H 2 4 H Fe 4 e - 1 Iron Substrate Anodic Region Cathodic Region 1. xidation of Fe yields electrons which travel through the metal. 2. Electrons at the Fe (inactive) cathode reduce 2 to H The Fe 2+ migrates through the drop and reacts with H 2 to form rust.

7 Relative Bond Strengths Force Type example E (kcal/mol) Covalent 1 Most rganics Metallic 1 Metals H bonding 2 Water <12 Dispersion 2 Most Molecules <10 Dipole 2 Polar rganics <5 Induction 2 Non-polar rganics <0.5 Force Type example E (kcal/mol) Paint Film to Metal 2 DTM Coatings <25 Water to Metal 2 Coating Defect 40-65

8 Coating/Substrate Adhesion Promoter Resin rganic Corrosion Inhibitor Improved adhesion between coating and metal substrate Coating/Substrate interface

9 Adhesion Leads to Corrosion Protection Non-Skid Paint; 2K Solvent-borne Epoxy Polyamide With Poor Adhesion Non-Skid Paint needed better corrosion resistance. Needs to withstand 2000 hrs salt spray with minimal corrosion in the defect sites created by aircraft damage

10 Adhesion Leads to Corrosion Protection Primer w/o HALX Primer With HALX rganic severe corrosion creep reduced corrosion creep

11 Mechanism: Hydrophobic Film Formers Film Formers: Slow both anodic and cathodic reactions rganic Benzoates Amines Sulfonates Thiols Di-acids - NH S - - S -

12 Multi-functional Anti-Corrosive (2) N S S (3) - - (1) (4) (1) Polar end: adsorption & strong affinity for M + / M leading to hydrophobic dense film formation. Also the Acid -Base reactivity site for modification (2) Electron donor site (3) Polycyclic aromatic: corrosion inhibition of non-ferrous substrates. Electron donors (N, S, ) (4) Non polar end: van der Waals interaction with multiple organic binders (Compatibility). Also electron donor to substrate

13 rientation of Molecule Impacts electron sharing capacity Dynamic action, changes during film formation and cure Imparts a surface tension gradient DTM adhesion Intercoat adhesion (pigment affinity)

14 Multi-functional Anti-Corrosive Adsorption of molecule forms a complex which increases the electrical resistance of the substrate Makes the oxidation of steel more difficult A form of active corrosion protection

15 Adhesion Promotion Electrons adjusting to lowest energy state (wetting) Dipoles formed during cure (intercoat) Polymer chains exhibit 1 bonding (coupling) Binder Substrate

16 WATER PERMEATIN (%) Barrier Properties No Inhibitor 4% BTTSA-amine Reduced 34 Water 25 Permeation in 2K Epoxy System determined by EIS No Inhibitor 4% HALX rganic TIME (days) 16

17 Coating Galvanized bjects Zn 2+ migration under film accelerates adhesion failure in susceptible systems Barrier type organic corrosion inhibition mechanism

18 18 RGANIC HYBRIDS 1. SILICNE ESTER HYDRLYZES T FRMS SILANL R Si R R H 2 R Si H R + RH 2. SILXANE BND FRMS R Si H R + H H H H SUBSTRATE R Si R Si SUBSTRATE + RH 3. GELATIN (CRSS-LINKING) PLYMER R Si R Si Si Si Si Si + H 2 + RH SUBSTRATE SUBSTRATE

19 Sol-Gel Treatment for Improved Adhesion Substrate: Hot dipped galvanized G70 70 U (ACT labs) Pretreatment application: 10% Hybrid Sol-Gel Cure: Air dry 24 hrs at RT Coating applied: Sherwin Williams high gloss water-based DTM at 50 µm DFT Accelerated test shown: 336 hrs salt spray

20 Ion-Exchange Notable Synergy

21 Ion-Exchange Inhibitors Significant release of energy by altering electron environment Decreases the densely packed electron structures of Alkali Metals Binds the strongest, most electronegative atoms and compounds, ex. Cl - and S 4 2- Significant synergy with Sol-Gel over Aluminum

Adhesion in Coil Coatings After 400h salt spray

Primer : TPA, phenolic resin, phosphoric acid

scribe (mm) 5 2 1 under-rusting at scribe (mm) 0 0

inhibitor Commercial 5% Ion-Exchange Substrate:

5 under-rusting at scribe (mm) 0 0 0 under-rusting

22 Adhesion in Coil Coatings After 400h salt spray test ASTM B Without Inhibitor Commercial system (SrCr 4 ) 4% HALX rganic 18.5% Ion-Exchange Substrate: hot dip galvanized steel Primer : TPA, phenolic resin, phosphoric acid pretreatment Topcoat: PES Melamine de-lamination at scribe (mm) under-rusting at scribe (mm) After 1500h Salt Spray Test ASTM B Without inhibitor Commercial system (SrCr 4 ) 4% HALX rganic 18.5% Ion-Exchange Substrate: Al/Zn steel Primer : TPA, phenolic resin, phosphoric acid pretreatment Topcoat: PVC Plastisol de-lamination at scribe (mm) total 0 0 de-lamination at cut edge (mm) total under-rusting at scribe (mm) under-rusting at cut edge (mm)

23 Ion-Exchange CNTRL EXTENDER PIGMENTS rganic(2%) Ion-Exchange(9%) 500 hours Aluminum Filiform Corrosion Test (1.2 mil epoxy primer, 2.0 mil PU topcoat)

24 Hybrid Synergy with Ion-Exchange 3% Sol-Gel + 0.7% Ion-Exchange Solvent Based Polyester/Acrylic Hybrid coating Good gloss for Aluminum wheels The film thickness of µm Filiform corrosion is < 1 mm

25 rganic Corrosion Inhibitors Anodic passivation (reduce rust & flash rusting) Improve adhesion Increase water resistance Reduce blistering Form protective films (adsorption) Increase coating flexibility (plasticize) Increase chemical resistance

Dynasylan SIVO 110. Description. Product Information. SIVO SOL Technology for coating systems

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