Trusses not a deck but, what do y’all think is causing the black discoloration? I’ve been led to believe it is a rust or iron stain. Or black tannin?
To simplify it, it’s not organic. Already tried several different SH ratios on it. And it’s not dirt, I used simple green and scrubbed it, I also used high pressure which removed a small amount of the black but most stayed the same.
Going to try a rust remover next weekend any thoughts? People have also mentioned oxalic acid?
