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Corrosion of fasteners in ACQ treated wood

GoalsCompare the corrosion of fasteners in ACQ

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Corrosion of fasteners in ACQ treated wood

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    1. Corrosion of fasteners in ACQ treated wood Newsha Ashari and Sofya Soldkin Tree Island Industries Ltd. John N.R. Ruddick UBC

    2. Goals Compare the corrosion of fasteners in ACQ & CCA treated wood. Identify the best nail coating suitable for ACQ treated wood.

    3. Materials Nails Selected for the Corrosion Test had been advertised by Suppliers to be suitable for ACQ application. ACQ & CCA Wood samples were purchased from local Home Depot.

    4. List of Nails Tested

    5. List of Nails Tested

    6. Corrosion Resistance Testing Protocol Testing for Mechanical Damage Prior to Exposure in Environmental Chamber. Exposure to the surface of treated wood. Duplicates the real life worst case scenario: Corrosion under the head and between the two surfaces of the connected timber.

    7. Corrosion Resistance Testing Protocol 4 Nails of each type driven into the wood Extracted by splitting the wood, Placed between the gaps of sandwiched ACQ & CCA treated wood in a randomized positions.

    8. Corrosion Resistance Testing Protocol Exposure to Continuous Water Fog (Moisture with no salt). Follow up investigation of the effect of Water Repellant on Corrosion of hot dipped galvanized nails in ACQ treated wood.

    9. Corrosion Resistance Testing Protocol Time Intervals in the Environmental Chamber: 188, 380, 644, and 830 hours, Temp 49 °C (120F) Continuous Water Fog. At each time interval, wood samples were removed, disassembled, and nails inspected visually

    10. Observations & Results The testing was concluded after 830 hrs as perforation of coating & the beginning of red rust was observed on HDG nails. Visual Inspection: corrosion started earlier & appeared more severe in ACQ compared to CCA treated Wood.

    11. Observations & Results Methods Used to Evaluate Corrosion Level: Visual Observation Diameter Loss (Steel Core Cross-Section Reduction) Weight Loss Bending Yield Strength Testing

    12. Observations & Results HDG in ACQ Treated Wood (Visual Observation).

    13. Observations & Results Coating #3 in ACQ Treated Wood (Visual Observation)

    14. Observations & Results Coating #4 in ACQ Treated Wood (Visual Observation).

    15. Observations & Results Coating #5 in ACQ Treated Wood (Visual Observation)

    16. Observations & Results Stainless Steel in ACQ (Visual Observation)

    17. Observations & Results Bright Nail in ACQ Treated Wood (Visual Observation).

    18. Observations & Results Coating # 8 in ACQ Treated Wood (Visual Observation).

    19. Observation & Results Diameter loss (Steel Core Cross-Section Reduction) Measured with Caliper to the accuracy of 0.0001 inch

    20. Observations & Results Cross-Section after Corrosion imposed on the original. Coating #3 Coating #4 Coating #5 Hot Dip Galv.

    21. Observations & Results Weight Loss. Ultrasonic Bath used to clean the corrosion Products. Less Accurate than Diameter Measurement Due to Difficulty of Removing Corrosion Products.

    22. Observations & Results (Cont.)

    23. Observations & Results Bending Yield Strength

    24. Summary The Reason for Higher Fasteners Corrosion Rate in ACQ compared to CCA is due to the: Larger amount of copper in ACQ. Copper is “Noble” metal and causes electrochemical reaction with less Noble metals Active ingredients in ACQ not corrosion inhibitors; chrome & arsenic in CCA serve as inhibitors Quat in ACQ is surfactant - absorbs water. Chromate in CCA is water repellant, lowers moisture content.

    25. Summary Best Nail Coating Suitable for Use with ACQ Treated Wood. Stainless steel has an outstanding performance compared to any nail coating. It has the similar electrochemical potential as copper, hence no copper induced corrosion. TII Hot Dip Galvanized after forming to ASTM A153 Class D demonstrate good performance in the ACQ treated wood. All other coatings show higher corrosion rate compared to HDG nails.

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