What are these black spots on my brand new treated pine deck?

[lmg]

Hi,

I've just had a new deck installed with treated pine. I was about to oil it but I've noticed these black spots appear on a number of boards. Does anyone know what this is and how to fix it? Many thanks.

[EricL]

Hello @lmg 

Welcome to the Bunnings Workshop community. Its sensational to have you join us, and thanks for sharing your question about your decking panels.

How long have the panels been installed on your decking frame? These appear to be tannin oxidation reaction (also iron-tannin reaction). This is a natural reaction that occurs when wood comes into contact with base metals such as iron. The tannins in the wood oxidize and cause discolouration. I suggest using Cabot's 1L Deck Clean to clean the surface of the deck before you oil the surface.

Here are some handy step-by-step guides:

• How To Clean A Deck
   
• How To Sand A Deck
   
• How To Oil Your Deck
   
• How To Maintain A Deck

If you need further assistance, please let us know.

Eric