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I have some projects coming up for the garden and I want to use some screws with the raised beds. I recently was told certain screws get 'eaten' by the chemical used for treating the lumber. If this is true, what screws will last longest with the treated lumber?

  • Treated or untreated doesn't often matter, the application can determine the appropriate screw (e.g. softwood, exterior use, self-tapping) and then you have to pick the head style, and whether it needs salt resistance or not. Expect some sticker shock with better-quality screws! – Graphus supports Monica Mar 22 '18 at 13:07
  • "I recently was told certain screws get 'eaten' by the chemical used for treating the lumber." When you hear anything like this always seek some specifics from the person because this is far too vague to be useful. – Graphus supports Monica Mar 22 '18 at 13:08
  • @Graphus i tried getting more information from my shop teacher but then he went on as to how he forgot what screws are not supposed to be used with treated lumber, which is why I asked the group. – Ljk2000 Mar 22 '18 at 14:07
  • Don't you just hate that? "Oh I forget the specifics but..." Not knowing the specifics never seems to stop people handing out well-meaning advice anyway! Anyhoooo, about the screws, while hot-dipped galvanised and stainless screws are both good choices they are not the only ones you can use. There are numerous multi-coated screws available that are also fine to use with all treated woods. See this on the Wood Magazine site for a little more. – Graphus supports Monica Mar 23 '18 at 17:28
  • That said, not knowing the specifics can still help people... if indeed some screws are unsuitable for certain types of timber then that at least points people in the direction of doing further research to find out whether that is true or not and if so which types. – WhatEvil Apr 4 '18 at 9:49
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Pressure treated lumber is treated with Alkaline Copper Quaternary (ACQ), an environmentally friendly water-based preservative that is free of arsenic and chromium. However, ACQ treated lumber is more corrosive to metal, so the right fastener is key to a safe, long lasting deck, fence or other outdoor project.

When nails are exposed to ACQ, a chemical reaction occurs, which accelerates the corrosion rate of the fastener. In addition, the organic components of ACQ attract water, further increasing corrosion on the fastener.

The wood treatment industry recognizes the corrosive nature of ACQ in relation to fastening systems, and recommends hot dipped galvanized or stainless steel nails be used. Hot dipped galvanized nails must meet American Society for Testing and Materials (ASTM) A153 Class D standards and stainless steel nails should be made from grade 304 or 316, to provide maximum corrosion protection. If screws are used they must be rated for ACQ.

(source www.treeisland.com/company/news-events/what-fasteners-work-acq)

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Galvanized and coated deck screws rust in treated pine; I am sure it has very little to do with the treatment. The first screws failed at about 10 years but a few lasted 20 years. I expect the stainless replacements to last much longer; The box indicates they are 316 SS which is likely true. Driving the heads down into the wood makes it worse because the recess retains water. I looked at the reference regarding corrosion and it listed no source for the corrosion reference, so I still doubt it. However I built my deck in 1996 so used CCA wood ; The EPA did not require the new crap until 2003. I am/ was a NACE certified Corrosion Specialist ( # 1635 , I have not renewed my certification) so I am not impressed by random articles regarding corrosion.

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Second answer:If you are using "deck wood" ( aka 5/4") it doesn't make much difference, the wood and the coated or galvanized screws or nails all last roughly 10 years. If you build a deck with the much stronger, longer lasting 2" X lumber, use stainless screws, period.

  • Thank you for more information, it does help me out. Also, you might want to edit your previous answer and add the new information.... – Ljk2000 Mar 29 '18 at 17:47

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