This post was updated on January 18, 2023
How To Fix Black Spots on Deck?
We get this question about 50-100 times a year at DeckStainHelp.com. Well, actually consumers want to know what causes the black stains to form around their nails or at the bottom of the metal furniture on their deck. Most are not aware that metal, when it rusts, will turn black in wood.
Nails Rusted on Deck
Nails rusting on a deck is not common but can happen from time to time. We have found that this happens for a couple of reasons.
- Non-Galvanized Nails were not used during the building process. When a deck is installed you must use Galvanized Treated Nails and Screws or Stainless Steel Nails and Screws to prevent the black rusty spots from occurring around the nails.
- Galvanized nails or screws were used but over time the protective coating has failed. This could take many years to occur but does happen. We have also seen instances where the floor was power sanded and this shaved or removed the protective coating of the galvanized nails or screw from the top.
Metal Patio Furniture Rusted on Deck
Rust on a deck can also happen from older metal furniture left in place for many years. We have also seen this happen from grills and other metal objects. Always be careful when placing metal objects on your deck and lean towards using aluminum or stainless steel items.
How To Remove Black Rust Spots on Deck
In many cases, you can use a deck wood brightener to neutralize out the rust spots and restore the natural color. This issue with this method is it will not prevent the nails or screws from rusting again once it rains. The only way to stop the rust from coming back in this scenario is to remove the nails or screws and replace them with new stainless steel or galvanized screws. This is not an easy option as it may cause damage to your deck boards as you try to remove the rusting nails/screws.
How To Brighten A Deck Video – DeckStainHelp.com
If you have any questions about fixing black rusting nails on your deck, please ask below.
Please post a picture or two as well!
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As an article and comment contributor to the site, Scott has been around the pressure washing industry since attending college. In 1993 he started his first company called Oakland Pressure Wash specializing in exterior pressure washing and deck staining. That company evolved into OPW L.L.C. shortly thereafter concentrating more on exterior wood and deck restoration. Scott and his Deck Cleaning Michigan company have restored over 10,000 decks in the Metro Detroit area since the early years. He has become an authority in the deck restoration industry and has contributed to numerous wood restoration forums and informative sites.
All the products he suggests through this site are sold through online sites and in retail stores, allowing the consumer to choose their own means of purchase. Scott’s eCommerce sites do sell many top brands he endorses and if you appreciate any of the help he has offered then feel free to purchase from one of them.
Why was my question and statement posted 9/7/2022 removed unanswered?
No idea what you mean?
My original question / statement is back up below this reply. It was removed for awhile after I posted it. My question concerns having no black rust marks on my deck prior to or even during cleaning brightening process with Restore A Deck they showed up a few days later after rain stopped before I could stain. Deck is 14 months old and had no marks whatsoever before using that cleaner/brightener combination. The black rust marks are around all the deck screws and since they were not there before cleaning how could the cleaner not be the cause? Thank you
Comments are not removed, they have to be approved after posting. This is explained after you post every comment.
No, a deck cleaner is not the cause. It is not aggressive enough to remove a galvanized screw coating.
I had zero marks around my 1 year old unstained pressure treated lumber deck until I used Restore A Deck cleaner and brightner. It rained for two days and when rain stopped today I see the black marks around the deck screws. This deck has been rained on and snowed on (Central New York even used ice melting products in winter on small section of deck) for 14 months and there were absolutely no marks around any of the deck screws, in fact, they were barely visible! How do you explain rust from using the wrong screws not showing up until I used Restore A Deck which you gave such a great review? Now I’m stuck with TWP semi transparent stain I can no longer use and will have to paint deck dark brown as trying to replace every screw in deck would be almost impossible and may damage boards.
Not a RAD cleaner issue but a screw issue. RAD prep products are used on many 1000s of decks per year without issues. You are blaming the wrong thing. Prep products do not cause rust. Metal rusts and your screws coating did not protect properly and failed.
BTW, to remove rust stains form screws a wood brightener would work.
I really appreciate your answer but had I not cleaned the deck I would have no black marks I believe I read they would continue to bleed through even if I brightened again? If I did same deal with letting entire deck dry for 48 hours and then use dark brown solid stain and that will fix ?
No, the cleaner products do not damage screw coatings that are properly manufactured. There is an issue with your screw batch.
You are blaming the wrong thing.
FYI, read the reviews for the screws on HD in the 1-star. A lot of issues with breaking or coating coming off within a year. Once this happens, they will rust. Bad batches have happened and you have one.
Thank you. None of this made sense to me until the OPW online store that sells TWP explained that during the cleaning process the friction from using a pressure washer or deck brush or sanding could strip the coating off the nail heads that were a bad batch or the wrong material and then they would subsequently rust. So I was correct in my assumption that the rusting was associated with the cleaning process – I used a deck brush – but I was incorrect in my assumption in was the cleaner that was the culprit. Just wanted to pass this on to your readers because it helped me to understand more. I appreciate your responses and the info on this site.
Wouldn’t the water rinsing the brightening agent just bleed out the rust again?
Hard to say if it will or will not come back.
I have a large deck that was stained with Sherwin Williams solid deck stain. It is starting to peel, and I would like to remove the solid stain and re-stain. Does the deck stain/paint remover take most of the solid stain off? Also, I have 1 by cedar wrap, and railing support as well. Would it be good to pressure wash and seal for the lasting raw cedar look?
A stripper will not remove a solid color deck stain fully. You can strip off as much as possible and then sand the rest off. Use one of these stain brands after: https://www.deckstainhelp.com/the-5-best-deck-stain-reviews-and-ratings/
I have black rust spot from nails on my redwood fence- the redwood is untreated (we live in So Cal and have very good weather). The fence is beautiful other than the eye sores: black streaks around all the nails (just like your pictures show). Is there a way I can spot treat to remove the stains, without having to then stain the entire fence?
I have tries TSP (made the TSP, bleach and water mix, as well as the TSP water mix) , hydrogen peroxide solution, dawn soap (that cleaned the fence but did nothing to the black marks), oxalic acid. But all those change the color of the wood, significantly.
I’d love some feedback, guidance and help.
We love the color of the fence and do not want to change it at all by staining it.
Thanks in advance
Wood Brighteners will remove most rust spots but they will come back as soon as it rains. Applying a stain or sealer over it after will not prevent it from happening again. The only way to fix is to replace the nails and use properly treated nails or screws.
Thank you so much for the reply. Can I use the Wood Brightener to spot clean the rust spots?
Or would that change the color of the wood? In those spots
I am attaching pictures
Thank you in advance, if any of your products would work I would be thrilled
You cannot spot apply a brightener, all wood will need to be coated evenly.
Hello, first I’d like to thank you for this site. The best collection of information I’ve found. So I used pressure treated pine with bronze coated screws for a deck I built last summer. Most of the boards have cupped, so my plan was to flip them over, clean with oxiclean, brighten with oxalic acid and seal with Seal-Once clear. I tried this on a couple of boards, and it worked well, except after using oxalic acid to brighten the test boards, I got these black spots around the screw holes (screws had been removed). Any ideas of what caused them and how to get rid of them? Thanks again.
It is rust. The screws have gone bad or the coating has failed. Brighteners typically will remove rust spots in the wood.
Why are my nails rusting and bleeding out black stains on our brand new pressure treated deck and what should I do to fix this before staining it so they won’t show through?
Bad nails or the wrong ones were used. You cannot fix this issue permanently outside of replacing all the nails and using proper galvanized nails or stainless steel screws. Once that is done, you can use a wood cleaner and a wood brighener to remove the black prior to staining.
My treated wood was built in 1991 and the old galvanized screws have the black rust stains. The deck is stained with a solid color deck stain. I would like to seal the rust stains and restrain with a solid color stain. I used the rust oleum rust sealer but it failed. Any suggestions beside Deck Brightener
You cannot stop rust stains from your screws with a sealer and you also cannot seal first and then apply a solid stain over a sealer. The sealer will repel the stain and it will peel. Your best option is to replace all the bad screws and then solid stain all after prep.
I need to re-stain our textured no slip deck. Do I have to remove all the old paint before I re-texture it? And I’m getting conflicting reports on which textured stain is the most durable for both snow and sun extremes.
You will have to remove it all first. Once that is done, try the Gulf Synthetics coating.
How???? I’ve already power washed it 2x and sanded 🤦🏼♀️🤦🏼♀️🥵
Power sanding to remove all. https://www.deckstainhelp.com/why-sanding-a-deck-can-be-an-issue/
Will a good water seal like Thompson’s prevent the rust from oozing out again?
No, it is not possible to stop it.