Polycarboxylate Inhibitors May 2018 Presented to: Potential Licensees NAVAIR Public Release 2018-437. Distribution Statement A: Approved for public release, distribution is unlimited Presented by: Craig Matzdorf NAWC-AD Senior Engineer
Background Polycarboxylate inhibitors show promise as inhibitors for improving the performance of Al-rich and other metalpigmented primers as well as on their own in primers and other applications Combinations of inhibitors have been discovered to perform synergistically Inhibitors have been assessed electrochemically in solution and as additives to Al-rich primer Additional polycarboxylate compounds are being studied by themselves and in combinations to optimize the best combinations for primer applications on steel, aluminum and both (mixed metals)
Definitions LP6-F58: base Al-rich composition with no additives. This composition is most sensitive to and most effective to highlight the effect of additives. LP6-FQ58: best Al-rich composition with alternative additives Inhibitor Blend 1: Mixture of Compounds 1 and 2 as shown in slide 7. Compounds 1 and 2 are two different polycarboxylates with the same cation. (focused on maximum corrosion resistance of aluminum and steel) LP-RED4.2: modified version of LP6-F58. Similar corrosion performance without additives. Inhibitor Blend 2: Blend 1 plus an additional compound (focused on maximum corrosion resistance of aluminum)
Results on Steel Coated with Al-rich Primer Phosphated steel panels after 30 cycles (days) of GMW 14872 (MIL-DTL-53022 Type IV test duration) LP6-F58 control LP6-FQ58 control LP6-F58 with Inhibitor Blend 1
Results on Aluminum Coated with Al-rich Primer 2024-T3 aluminum panels with Type II conversion coating after 83 days/cycles of GMW 14872 LP6-F58 control LP6-F58 with Inhibitor Blend 1 LP6-FQ58 control
Results on Aluminum Coated with Al-rich Primer 2024-T3 aluminum panels with Type II conversion coating after 2000 hours of ASTM B117 LP6-F58 control LP6-F58 with Inhibitor Blend 1 LP6-FQ58 control
Steel Electrochem Samples after Testing No inhibitor- anodic scan ph 6.14 6.56 Compound 1- anodic scan ph 5.59 10.38 Compound 2- anodic scan ph 6.20 7.80 Blend 1- anodic scan ph 5.75 6.31 No inhibitorcathodic scan ph 6.14 4.70 Compound 1- cathodic scan ph 5.59 5.98 Compound 2- cathodic scan ph 6.20 6.25 Blend 1- cathodic ph 5.75 5.70
Blend 2 Results 2024-T3 aluminum panels with Type II conversion coating after 2000 hours of ASTM B117 and 104 cycles (2500 hours) GMW 14872 exposure LP-RED4.2 B117 control ASTM B117 GMW 14872
Electrochemistry of Inhibitors in Solution Polarization data and pictures show a large decrease in current output for steel and aluminum and impressive inhibition in 3.5% salt water solution (decrease in current) for Inhibitor Blend 2 Control Blend 2
Opportunity A wide variety of solubilities and chemical combinations is possible to tailor to applications of interest Compounds have low toxicity and support the elimination of hexavalent chromium and zinc from corrosion-inhibiting coatings