How Do You Fix a Rusted Mower Deck? (Step by Step)

How Do You Fix a Rusted Mower Deck? (Step by Step)

If you're a lawn care professional, you might have to deal with rusted mower decks. We know how annoying that can be! So, We want to help by showing you how to fix a rusted mower deck. We've figured out a few different ways to fix a rusted mower deck. 

We have tried everything from the good to the bad to the ugly. To save you from having to deal with the hassle of the "ugly" method, We are going to explain how you can fix a rusted mower deck (with a step-by-step guide).

A rusted mower deck should not be discarded and replaced. It is possible to fix it. In most cases, you can fix rusted mower decks yourself without consulting a mechanic. Just figure out if the rusted mower deck repair is actually worth it before you break out the fiberglass and epoxy.

Identifying the problem (How to find it)

You need to examine the areas that need to be repaired and decide whether it is structural, such as an engine mount, or non-structural, such as a hole in the deck. Usually it is the latter, since rust on a mower deck is a very common problem. I'd say your mower deck is probably beyond repair if the wheels are gone and the engine is holding on. But if it's just a hole, here's what you'll need to fix the rusted mower deck.

A Tool List for Fixing Rusted Lawn Mower Decks

Now that you have all the tools and materials for fixing a rusted mower deck, let's go over the process in more detail. The following is an overview of the process so you can get a sense of what's required, along with some items to consider when you're setting up your workspace.

  •  Preparing the Workspace
  • Ventilate the Area Where You’re Working
  • Clean the rusted areas
  • Remove damaged metalwork
  • Grind or file back rusted surfaces
  • Apply anti-rust paint
  • Trim the glass matting
  • Mix the Resin and the Activator
  • Install fiberglass matting
  • Repeat application of fiberglass matting and activated resin
  • Allow hardening
  • Sand back resin to a keyed surface
  • Apply paint and protective coating

You may already be familiar with the application process of fiberglass. You may feel confident enough to repair the rusted mower deck right away, but if you're somewhat like me, you might need a little more guidance. Using this guide, you can start repairing your rusted mower deck with confidence.

1. Prepping the Workspace

Preparing your workspace is the first thing you should do. There must be enough space to work on both the top and bottom of the deck at the same time, with plenty of space for all your materials and tools.

Make sure you have enough room to move around your work area by pulling out your workbench or a table. Having this space can be anywhere, such as a garage, driveway, or corner of your yard. If you want your partner happy, don't put it in the kitchen or lounge.

You'll need to get some help getting the mower up on the bench or table; I usually offer a neighbor a cold beer to assist. Before continuing with the repair, it is imperative that the mower is positioned correctly. You will need to tilt the deck so you can access the underside. 

You can use either a jack stand or a paint tin to support the deck. Make sure it's firm and that the mower won't roll. Once activated, the resin cures quickly, so don't waste time fumbling around looking for things.

2. Make sure the area where you're working is well ventilated

If you've ever worked with resin before, you are probably aware of the toxic fumes it creates. It is very important that you ensure that your workspace is well ventilated at all times. Most of you don't have an extraction system, but opening the windows will serve the same purpose. You can also do the work outdoors. This is also an option!

3. Clean the rusted areas

When you begin any kind of repair work, you need to ensure that you have your protective equipment with you. The most important thing that you need to do at this point is to wear your gloves, face mask, and eye protection.

You will start by cleaning the mower deck with a wire brush before performing the rusted mower deck repair. Remove all dirt and grass from the deck so that the exposed surface is ready for rust removal.

4. Straighten Things Up

Take the hammer and knock the loose rust off and bang down any rusted-in areas. This is the part where you are going to tackle the bits that the wire brush could not handle.

5. Remove damaged metalwork

After you have done what you can with the wire brush and hammer, move on to the parts of the deck that are not worth saving (the completely rusted ones). You will need to remove all the rust and leave only the unoxidized metal.

As rusted parts are fragile, it will be necessary to remove them so that a good, firm surface can be established. Grab your grinder (or metal file if you don't have one) and start removing rusted material. I would recommend repeating items 3 through 5 taking your time and using the right tool for the job.

6. Apply anti-rust paint

The next step is to apply rust-inhibiting paint to the areas where you have been working. After applying the first coat, wait at least 10 minutes before applying the second coat. Using Tannic Acid with Organic Polymer inhibitors, rust is converted to Iron Tannate. As a stable material, you won't have to worry about areas you couldn't reach.

7. Trim the glass matting

Next we'll talk about fiberglass matting. With your scissors, cut the matting into the pieces needed to cover the patch area. I recommend that you allow two inches of overlap around the patch. If the hole is 6 inches wide, I would cut the mat to 10 inches wide, giving you a 2-inch overlap all the way around.

In my experience, 8 layers of matting once epoxied give me about 1/4-inch thickness overall, so I would suggest preparing 8 pieces of matting for your rusted mower deck repair. Once the pieces are cut, you can set them aside for later use.

8. Mix the Resin and the Activator

At this point, you should be ready to mix the resin with the activator. Please take a moment to prepare the area for the application by double-checking that all steps 1-7 have been completed. Please grab your resin, resin hardener/activator, a mixing container, a measuring cup, and a mixing stick. Follow the manufacturer's instructions for mixing the required quantities.

9. Apply the Glass Matting

Apply liberal amounts of mixed resin to your mower deck where you intend to fix the rusted part using one of your paintbrushes. Set a piece of precut glass matting in position. After that, you can paint on a new layer of epoxy using your paintbrush. The epoxy should be liberally applied.

The matting should be applied alternately on the outside and the inside, if possible. Repeat this process until you have applied all eight pieces of matting, then give it a final coat of epoxy. Now you can sit back and wait for it to fully cure.

10. Sand back resin to a keyed surface

After the epoxy has cured, grab your sandpaper. You need to sand the fiberglass lightly to ensure that the finish paint adheres well. You can use 80-grit sandpaper for this. What you want will be a dull finish on the fiberglass.

11. Apply a Finish Paint

Apply several coats of your chosen finish paint on the outside. I hope you chose a similar color. If you want to give your underside a long-lasting protective coating, I recommend using two-part epoxy, high durability paint. Although it may be more expensive, it will prevent rust on a mower deck in the future.

Other Options to Repair Your Mower Deck

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When it comes to repairing a rusted mower deck, there are other options to consider that may be more suitable for certain circumstances. For small holes, such as those that are about the size of a penny, you can replace the fiberglass with a 2-part epoxy metal putty that will attach the rusted mower decks.

Remove steps 7 thru 9 from my step-by-step guide and replace them with my putty approach:

  • Mix the 2-part epoxy putty according to the manufacturer's instructions
  • Apply putty to the required area
  • Allow the putty to partially pass through the hole by applying pressure
  • By applying pressure on either side of the repair, the putty will hold itself in place
  • Allow curing then continue to step 10

You may want to consider metal patching if you are trying to fix a rusted mower deck that is beyond the abilities of even fiberglass for something such as a big commercial deck. There will be a variety of tools required for this kind of work such as a welder, metal cutters, rivet guns, and patch metal itself.

As before, we can replace steps 7 through 9 with metalworking techniques. I would not recommend this technique for your small walk-behind-mower, as the metal used is usually much thinner and may not be suitable for welding.

Conclusion

The mower deck is the part of the lawnmower that cuts the grass. The deck is usually made of metal and sometimes plastic. It is important to take care of your mower deck so that it does not rust.

There are a few ways to make sure your mower deck does not rust. You can wash it with soap and water, let it dry, and then coat it with an anti-rust spray or liquid. You can also use paint thinner to remove any rust from the metal before applying a protective coating.

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