Coated the bottom of my mower deck with POR15

[Jrblanke 840]

My 42" SD was in pretty good shape, and I would like to keep it that way. Knowing that I am not going to hose it off after every use, I figured I needed to take some measures in protecting the bottom so it will last as long as possible.  When I started this project last fall, I was planning to replace all the hardware with stainless. I was also planning to remove all of the spindles and disassemble them for inspection, but other priorities came about and I put it off until I blew up my 876 in June (that's another story) and I had to get another mower back in service.

I used a POR15 "starter kit" to seal the bottom of the deck  I also put some on the top where I noticed rust from where grass collected under the belt guards. POR15 is advertised as a sealer that can be applied directly over rust, and does not need a primer to adhere properly. I don't have a sand blaster, so something that I could get clean enough with an angle grinder and garden hose was important. It is kind of expensive, but I figured out that there is a starter kit that is under 25 bucks, and is advertised to cover 6 ft^2. It was enough to do 1 deck and probably enough to do aa 32" or a push mower). 

The steps I took were:

1. Remove all caked on grass with a screw driver/ putty knife
2. Remove everything that bolts to the deck so bolt heads are not coated. (I didn't remove the spindles, because I ran out of time, and the outside of my spindles looked pretty beat up, and i didn't want to damage them by removing)
3. Use angle grinder w/ wire brush to remove any loose rust
4. Use POR15 marine clean to clean the bottom of the deck. I diluted this 4:1 water to cleaner and sprayed it on using a squirt bottle.  I let it set for about 15 minutes, then hosed it off. 
5. Use POR15 metal prep to treat the clean surface. After letting the deck dry, I used a foam brush to apply the metal ready solution to the surfaces that were going to be coated. I let it dry for 30 to 40 minutes to allow it to etch the surface. The metal developed a white zinc powder on the surface in this time. I hosed it off and let it dry over night. By the time I got back to it 2 days later, the surface had a developed some surface rust, but POR15 likes this, so I just wiped it down with a dry rag, and moved on to coating.
6. Coat the surface with POR15. Don't get this stuff on your skin because it will not come off for several days. It will not come out of clothing. Anyways, I applied with a brush and did 1 heavy coat. I put a second coat on the spots where grass had collected the most. 

I was very pleased with the results. Time will tell whether or not the coating holds up, but my confidence level is high, and as cheap as it was, I wouldn't hesitate to buy another kit and coat my other decks. 

Before grass removal of the bottom:


After wire brushing/cleaning/hose off:


After applying the metal prep, but before hosing it off:


After the metal prep was hosed off, and the deck was wiped down with a dry rag: 


Here is after I finished coating. It isn't pretty, but it will work. 

[pacer 3,159]

I have been threatening - and threatening!! to do this to a deck ..... but.... just never got around to it. Well, I think your nicely done write up, and pics is finally gonna prod me to do it! Course it helps that I presently have a 48" torn down completely and ready for paint, so I just think the afternoon I'll go pick up a can.

FWIW - the metal prep stuff is almost certainly phosphoric acid and I HAVE to have this stuff in my shop at ALL times what with these old horses having so much rust I use quite a bit of it. Like on this 48" deck, I sand blasted every piece and I then give everything a coating of it.  And yes, it will form a white powdery coating and will flash rust. Its not really a rust preventer but it kills any of the existing rust changing it to ---- um, iron phosphate?? (I'm not sure of that!)

[Racinbob 10,277]

I did the very same thing to my 42SD a few months ago. It seems to be holding up very well. After every mowing I scrape off the clumped grass underneath and the POR 15 acts like a teflon coating.

[Lane Ranger 10,495]

James:  I did this several years ago with POR-15 to a  36 deck and it is still going strong.   I did not change all the  carriage bolts on the deck at that time and I strongly suggest you do that before completing this preservation activity on this 42 inch deck.

[tommyg 152]

I would suggest topcoating the POR15. In my experience, it never seems to hold up all that well by itself. I know it doesn't like UV at all, although that's not a problem there. There's another product made by the same folks that you use to topcoat the POR15 prior to your final coat.

[Jrblanke 840]

Thanks for the suggestions guys! I hope it holds up!