I’m going to agree with Joseph on this one. You basically have two choices but both will require you to replace the screws. (Depending in the size of the screw that’s in there go with a stainless #8x2.5” trim head). I’d start by backing out a couple screws and hitting it with a sander to test how deep the staining goes. If it’s surface then you can replace the screws without flipping the boards and just give it a good sanding. Option 2) If staining is deep you can try flipping the board hoping there’s no staining on the underside and face screw the boards back down. Option 3) and one I would’ve recommended from the get go... Use a biscuit joiner like Joseph showed in the video and cut a slot in the side of the board while utilizing a product like the Eb-ty Precision Clips for Ipe which I believe are the best product in the hidden fastener market. Unfortunately though, if you go the hidden fastener route, now you’ll be looking at empty screw holes on the face of your boards. Whichever route you go, while certainly a bit of a hassle, the issue is pretty readily rectifiable. Part of the beauty of wood over composite decking. Worst case scenario sanding should solve the problem and you’re deck will look like brand new...

Thanks! Will pull some screws out and report back.

The only fastener that should be used anywhere in contact with hardwoods like Ipe is stainless steel otherwise you get the black oxidation streaks that you are seeing. DeckWise cleaner may help remove the stains but you still may end up having to sand the deck. Sine your contractor used an inferior screw we hope you do not have any snap on you when you back them out. If you do contact us and we have a solution for you so you don't have to buy all new boards. Also while we are guessing this is just a standard deck if that's the case you can use regular 305 grade stainless steel screws. If your deck is near saltwater you should use 316 grade stainless.

Thanks AdvantageLumber! What is considered near saltwater? I’m about 1.5 miles inland from the Pacific Ocean in San Francisco.

Studies have shown metals can corrode 10x faster near salt water than fresh water as much as 30 to 50 miles away. So you should be using 316 stainless. We have them with color coated heads to help blend in with the decking or just regular stainless if you don't care about the stainless look. If you want you could also countersink and put ipe plugs in over all the screws but that is more labor intensive but looks very nice and allows for easier sanding down the road so you are not sanding your screw heads so that's something to consider.

We agree with Advantage. You’d be fine with 305 as the difference between it and 316ss is de minimis, but certainly can’t hurt. You will want to adjust the torque settings on your drill though. 316ss is a little softer and more prone to snapping heads off.

I'd remove the screws and countersink and plug using 316 ss screws. It looks like you will remove most of the staining by countersinking.

I used barkeepers friend: made a paste with water and scrubbed wth a toothbrush. Some completely gone, other much lifhter