Sodium hydroxide and metal spindles on a deck

I have a deck to clean and stain.

I was considering stripping it down with sodium hydroxide. But the spindles are metal.

I know some metals don’t mix well with sodium hydroxide (eg aluminum). But I haven’t been able to find a list of metals that are ok with sh.

Anyone have any experience with metal spindles and sh?

If this isn’t the way to go, what would you recommend? Sodium percarbonate?

The current stain on there is oil-based TWP.

If you just gave them a price for cleaning don’t strip it unless you talk to the homeowner and significantly raise your price. It’s not like you just spray the stripper on and the stain comes right up. Depending on the stain it can be a lot of work. It’s a small deck so could be a good one to practice on if you think you even want to get into decks. A lot of guys on here don’t even mess with decks and especially when it comes to stripping. There can be really good money in decks but it can be tedious work. You just have to charge accordingly.

What’s the homeowner expecting? Do they just want it cleaned? Stripped? Did you test to make sure it’s oil based or are you going off of what they told you? Not that it’s that big of deal but they need to know in order to use the correct stain. You really shouldn’t have to strip it unless they want to go with a lighter color. I’d worry more about the Sodium Hydroxide stripping the paint on the spindles than hurting the metal. It would have to eat through the paint before it got to the metal. Plus, it would have to be on the metal for quite a while to do anything to it. It can definitely eat aluminum but it would almost have to be soaking in it. There’s not really a difference in stripping oil based stain or stripping paint.

Looking at the pictures I would just clean with Sodium Percarbonate unless they specifically said they want it stripped. It’s not very dirty and in good shape. Spray the Sodium Percarbonate, let dwell for 10 minutes misting water to keep wet if need be, hit deck boards with deck brush, maybe spray a little more percarb while brushing if you think it needs it, and then rinse. It’s a small deck so it will only take a few minutes to brush. I would then go over each board with about 800 psi. Start at one end and continually go to the other so you don’t have any start/stop marks. Neutralize with oxalic and rinse well. Recommend to them to stain with the same stain that was previously used.

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Is this your first job?

Thanks for the great advice!

Homeowner is easy to work with. They want a nice looking deck and will be happy if that’s the final product I give them.

I didn’t test for oil vs acrylic but I asked when they last stained it (2 years ago) and asked to see the can of stain.

They want to go with the same color. And I’ll be the one staining it.

Not my first job. I’ve done a lot of decks both pressure washing and staining. But until I stumbled across this forum, I almost never used chemicals. So using them on a regular basis is a new concept to me. And thus my familiarity with them is pretty low.

So my knowledge with chemicals is very limited–really just what I’ve read from you all.

Doing a great job is important to me so I didn’t want to be the old dog that’s not willing to learn new tricks. Thus, if chemicals help me do a better job, I’m all there.

That said, I’ve used the sodium hydroxide a handful of times with good results, but never with metal spindles getting pro-longed exposure to it. So I wasn’t sure what might happen there.

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@marinegrunt Is the sodium percarbonate mixed at the same ratio as the sodium hydroxide? 1/2 cup to 1 cup of percarbonate to 1 gallon of water

And do I brush the vertical surfaces as well?

Sounds like you have a pretty good grasp on decks or have at least tackled some before. It makes it nice when they still have the old stain can to look at. You might already know it but, for future reference, one way to tell waterborne between acrylic is with denatured alcohol. Put some on a white rag and rub the wood. If the rag brings up any color you have waterborne stain.

I usually mix sodium percarbonate at 8 oz per gallon. You can try 10oz but it might not all dissolve. Mix into hot water. It does have a shelf life so has to be used the same day. I usually mix mine the morning of and right before I leave for the job. Make sure your container is vented. I use a 5 gallon bucket with a plastic fuel filter poked through the lid.

I usually don’t brush the vertical surfaces unless they’re covered in algae. You’ll see the sodium percarbonate working right when you spray it on there. Sometimes you don’t even need to scrub. Looking at the deck above it might not even need it.

I mix oxalic at 8 oz/gallon too. Let dwell 5-10 minutes and rinse.

If you stain a lot of decks I would highly recommend investing in an airless sprayer. I’ll never do another deck without one. It might take an hour or two to tape and hang plastic but you can fly when staining. This 12’X24’ took me about 2 hours to spray 2 coats and that includes back brushing each coat.

Not sure why I made the pictures backwards here.

I don’t stain a lot of decks but I like to do them every so often to mix things up. Plus, there’s good money in them.


If it is already stained and being restained I go with bleach. If it is bare wood I typically go with a very diluted hydroxide/metasilicate blend