Last year I bought 60 prepainted hardie planks and wasn’table to get to myproject until recently, I wrapped themin plastic and stacked them on stickers on my deck. Now I am ready for them but as I unwrapped them, I found that water had gotten in and the pale green painted faces had blotchy white stains on them. these stains did not respond well to a scrubbing with a household floor cleaner. I am wondering if any one knows of a cleaner or solution that will remove them. I have a pressure washer. butthought it might be better to seek the advise of more knoledgeable pros. If the stains won’t clean off, could I repaint with out the stains striking through.would ithelp to re prime with Zprime or Kilz or some other product. I would like to salvag these planks, but as I got them for $5 each, Idont want to spend $8 each to make them work. Also. I probably don’t have enough time or good weather to paint them 2 or 3 times. any help or advice in this matter would be greatly appreciated.
Chris
Replies
Try vinegar or another mild acid.
The white is probably efflorescence, where the moisture draws the weaker constituents of the cement paste out. It is basically a lime deposit. Acids should disolve it.
Start weak, and then move up to the mildest acid that will disolve it.
I had a bit of this on some of ours that were stored for a while. I simply brushed some touch-up paint on them. Nothing bled through.