When I bought my house the 2 decks on the back were cantilevered (supported by floor joints extending outside the house), but they had never been cared for and were literally rotting off the back of the house. I decided to have those decks removed and replaced with decks supports by steel posts.
The steel posts will probably be standing when everything else is gone, but they are a maintenance issue since every nick or crack in the paint is an opening for rust formation. After 10 years there were quite of few rusty places and the white paint on the posts also had a black film developing so it was time to refinish the posts. All 14 of them. Groan.
I have a friend who is a boat captain who had great suggestions on how to clean up and refinish my rusted metal. His experience with metal boat hulls in salt water provided the best product imaginable for this huge project – Ospho. I had never heard of it and I can’t tell you how happy I am that I did. If you have exterior stuff that is rusted and you want to stop the rust dead in its tracks, this is the stuff to use. Quoted from the Ospho site “When applied to rusted surfaces, OSPHO causes iron oxide (rust) to chemically change to iron phosphate – an inert, hard substance that turns the metal black.” They list the stores that carry it on their website. http://www.ospho.com
There was no way I was going to completely strip all 14 posts so my plan was to remove all visible rust and bad spots, sand the remaining paint, and refinish from there.
While the write up for this project isn’t long, it was an extremely tedious multi-day project so I’m not telling anyone it’s easy. The results are awesome, however. The steps I followed would work well for any outdoor rust problem whether it’s posts, a fence, etc.
Steps of project:
- Remove all visible rust down to clean metal
- Sand entire posts
- Apply Ospho
- Apply Primer
- Apply 2 coats of paint
1. Grind off rusty areas. I had to get rid of the black film that was forming and I wanted to make sure there was no oil or grease on the posts, so I scrubbed them all down with a good cleaning solution first and let them thoroughly dry.
The instructions for the Ospho product I was going to use stated: “You do not have to remove tight rust. Merely remove loose paint and rust scale, dirt, oil, grease and other accumulations with a wire brush.” Despite what Ospho said, I decided to use a grinder with a wire brush attachment to remove all the rusty spots. I didn’t want a bumpy surface on the posts and I wasn’t sure how it would look if I left the rust, so I spent a couple days grinding away the rust.
2. Sand the posts. I wanted the primer and paint to adhere so I sanded the remaining paint with medium grit sandpaper and them wiped them down to remove the debris from grinding and sanding.
3. Apply Ospho. Ospho is a pale green liquid that is a little runnier than a gel. I used a paint brush and painted a coat of it on the posts from top to bottom, even over the paint in case there was rust that wasn’t yet visible to me. I let it do it’s thing overnight.
4. Apply primer. I wiped the posts down with rags to remove any powdery residue from the Ospho and applied oil base white primer and allowed it to dry overnight. My posts are white, so I didn’t want to start with a gray primer.
5. Apply 2 coats of paint. I lightly sanded the posts before each coat and applied 2 coats of oil base Rustoleum paint.
Doesn’t sound that bad, but I did this during Texas summer in 100 degree heat. Grinding the posts took a couple days, as did each coat of paint on that many posts. Due to high humidity I let everything dry at least 24 hours.
It was worth the effort, because the posts were back to snow white and beautiful.
