Do you have a mower that runs like a dream but shoots the grass out of rusty holes? Or are you that guy who, like me, missed the memo on the things you can do to keep your mower deck from rusting Along the way, I’ve figured out a few different methods on how to fix a rusted mower deck. I’ve tried the good, the bad, and I’ve even tried the ugly. In this article, I’m going to try and explain how you can repair a rusted mower deck (with a step-by-step guide) to save you from having to deal with the headache of the “ugly” method.
Firstly…Can a Rusted Mower Deck Be Fixed?
Yes, you can carry out most rusted mower deck repairs yourself without the need for a repair shop. You just need to work out if the rusted mower deck repair is actually worth it before you break out the fiberglass and the epoxy.
Diagnosing the Problem (What to Look For)
Take a look at the areas that need to be repaired and decide if the repair will be structural, like an engine mount, or if it’s non-structural such as a hole in the deck. It’s often the latter, as this is a very common problem experienced when rust affects a mower deck. If the wheels have fallen off and the engine is holding on for dear life, then I would suggest your mower deck is probably beyond salvage. But if it’s just a hole you’re dealing with then let’s take a look at the tools and materials you’ll need to get the rusted mower deck repair underway.
What You’ll Need to Fix a Rusted Lawn Mower Deck (Equipment List)
A hole can seem like a big deal at first glance, but nothing is going to get past a fiberglass repair. It’s tough, rigid, and can take a beating. Here is a list of items that you will need to get started:
- Wire brush
- Angle Grinder/Metal File
- Mixing stick
- Fiberglass matting
- Resin hardener/activator
- Mixing container
- Measuring container
- Rust inhibiting paint with Tannic Acid & Organic Polymer
- Finishing paint
- Protective coating paint
- Protective eyewear
- Face mask
How to Repair a Rusted Lawn Mower Deck (Step by Step)
Now that you have all the tools and materials for the rusted mower deck repair, let’s take a look at the process in more depth. Here’s an overview of the process so you can become familiar with what’s required, plus a few items worth mentioning when you’re prepping your work area.
- Prepare a well-ventilated workspace
- Position the mower so it can be worked on
- Clean down rusted area
- Knock down damaged metalwork
- Grind/file back rusted surfaces
- Apply rust-inhibiting paint
- Cut the glass matting
- Mix & apply activated resin
- Apply fiberglass matting
- Repeat fiberglass matting/activated resin application
- Allow hardening
- Sand back resin to a keyed surface
- Paint & protective coating
You may already be familiar with the application process of fiberglass and feel confident enough to move straight on with repairing the rusted mower deck, but if you’re somewhat like me, you probably would like a little more information on how to get started. Here’s my step-by-step guide you can follow to start repairing your rusted mower deck with confidence.
1. Prepping the Workspace
The first thing you are going to need to do is to get your workspace prepped. You’ll need enough space to work on both the topside and underside of the deck at the same time, with enough room for all your materials and tools.
Pull out your workbench or a table into the middle of your work area, giving yourself enough room to walk around. This can be in any space like your garage or driveway; I wouldn’t recommend the kitchen or lounge though if you want to keep your partner happy!
Now you’re going to want to grab some help to get the mower up on the bench/table; I usually do this by offering a cold beer to a neighbor.
Before starting the repair, the last thing to do is get the mower in the correct position. You will need to tilt the deck and give yourself access to the underside. You can use a jack stand or a paint tin; anything suitable to support the deck will be fine. Make sure it’s firm and that the mower isn’t going to roll away. The resin cures quickly once it has been activated, and you don’t want to be fumbling around looking for things when time is a factor.
2. Ventilate the Area Where You’re Working
If you have worked with resin before you’ll be aware of the toxic fumes it creates. You’re going to want to make sure your workspace is well ventilated. Not many of you are likely going to have an extraction system, but cracking open the windows will serve the same purpose. Or do the work outside in your yard. That works too!
3. Get Things Cleaned Up
When you start any repair work you need to make sure you have your protective equipment on hand. This is the point where you need to don your gloves, face mask, and eyewear.
Using your wire brush, you’re going to clean back the surface where you are going to carry out the rusted mower deck repair. You need to brush back all the dirt and grass leaving the exposed deck surface ready for tackling the rust.
4. Straighten Things Up
Grab the hammer and knock off any loose rust and bang down any areas that have rusted out of position. Here you are tackling the bits that the wire brush couldn’t handle.
5. Get Rid of the Rusted Material
Now that you have done what you can with the wire brush and hammer, it’s time to move on and address the areas of the deck that are just not worth saving (i.e. the completely rusted bits). What you need to do is cut out all of the rust and leave yourself with just unoxidized metal. The rusted parts will be fragile and need to be removed so that you have a good, firm surface to start with.
Grab your grinder (or metal file if you don’t have a grinder), cut away any rusted material, and start working towards a deck ready for fiberglass. My suggestion is that you repeat items 3 thru 5, taking your time and using the right tool for the job.
6. Treat the Rusted Areas
Next, you’re going to take your rust-inhibiting paint and brush, and give the areas you have been working on a coat. Let this first coat sit for at least ten minutes before applying a second coat. The Tannic Acid with Organic Polymer inhibiting paint converts rust into Iron Tannate, a stable material so you don’t need to worry about any areas you couldn’t reach.
7. Cut the Fiberglass Matting
Onto the fiberglass matting next. You need to cut the matting using your scissors into pieces that will cover the patch area. I would suggest that you allow for a 2-inch overlap around the patch where possible. If the hole is 6-inches wide I would cut the matting to 10-inches wide giving you the desired 2-inch overlap all the way around.
I’ve found that 8 layers of matting once epoxied give me a 1/4-inch overall thickness, so I would recommend preparing 8 pieces of matting for your rusted mower deck repair. Once the pieces are cut you can set them aside for later.
8. Mix the Resin and the Activator
At this point, you are ready to mix the resin and the activator. Take a moment to get the area ready for the application by double-checking you have completed steps 1-7 fully. Grab your resin, resin hardener/activator, mixing container, measuring container, and mixing stick. Using the manufacturer’s recommendations, mix the required amounts.
9. Apply the Glass Matting
Apply a liberal amount of mixed resin to the lip of the mower deck where you intend to carry out the rusted mower deck repair using one of your paintbrushes. Take a piece of the precut glass matting and lay it in position. Using your paintbrush you can then begin to cover the matting with a new layer of epoxy. Again, be quite liberal when applying.
In my experience, it’s best to alternate which side you apply the matting, one on the outside then one on the inside. Continue this process until you have applied all 8 pieces of matting then give it a final coat of epoxy. Now just sit back and allow it to fully cure overnight.
10. Sand Back the Surface
Once the epoxy has cured, grab your sandpaper. Give the fiberglass a light sanding so that your finish paint has a nice surface to adhere to. 80-grit sandpaper will do just fine. You want to sand the fiberglass to a dull finish.
11. Apply a Finish Paint
Take your selected finish paint and give it a few coats on the outside. Hopefully you picked a matching color. For the underside, I would recommend using a two-part epoxy, high durability paint so that you can give it a long-lasting protective coating. It may be a little more expensive, but it will keep a mower deck from rusting again in the future.
The Other Options You Could Try to Repair Your Mower Deck
There are other options when it comes to repairing a rusted mower deck that may be better suited in certain situations. If it’s just a small hole, say the size of a penny, then repairing the rusted mower deck can be done by swapping out fiberglass for 2-part epoxy metal putty.
Simply remove steps 7 thru 9 in my step-by-step guide and replace them with my putty approach:
- Mix both parts of the 2-part epoxy putty as per the manufacturer’s instructions
- Apply putty to the required area
- Apply pressure to putty allowing it to partly pass through the hole
- With a hand on either side of the repair, apply pressure to form an overlap with the putty so it holds itself in place
- Allow curing then continue to step 10
If you are addressing a rusted mower deck repair that you believe to be outside of the ability of even fiberglass on something such as a big commercial deck, you may want to consider patching with metal.
This kind of operation will require a whole host of additional tools such as a welder, metal cutters, rivet guns, and patch metal itself. Like before, we can replace steps 7 thru 9 and replace them with metalworking techniques.
This isn’t a technique I would recommend for your smaller walk-behind-mower, as the metal used is typically much thinner and may not be suitable for welding.