Of the tools we have around the house our lawnmowers are probably one of the more expensive items but the fact is we grow dependent on them so keeping them in good working order means they last longer and work better while we have them.
Over time no matter how well you maintain and clean the debris from the bottom of your lawnmower deck it will begin to rust. This is because even light grass blades will eventually cause enough friction to wear down the paint and once the bare steel surface is exposed it will begin to rust.
If you see this beginning to happen but you don’t have time to take care of the job right away you can make sure the surface is clean and then spray the underside with a light coating of oil in a aerosol can.
Eventually though you will need to paint the underside of your lawnmower deck and today we are going to do just that.
Preparing your Lawnmower for Paint
Before you begin work you should understand the dangers of working on your lawnmower when it is turned on its side. In my case I will be removing the spark plug wire and then the blade. This only takes a couple minutes but It can save you a trip to the hospital and a lifetime of pain. These things happen to professionals every day in the repair business so don’t think you’re so smart and it won’t happen to you.
The first thing you need to do is remove all of the rust or as much as you possibly can and to do this you can use a set of wire brushes but I really suggest you invest $15 and get an electric hand grinder and a braided wire brush attachment.
One really important thing about using a wire brush on a hand grinder is that the standard wheels where the wires are free are not designed to work with the speeds of your grinder. Grinders run at over 10,000 RPM and those wire wheels are rated to about 2500 RPM at most. What will happen and has happened to me is .. the wire wheel will work for a few minutes but as the ends of the steel fibers become lose they will shoot off at you like needles flying out of a dart gun. Luckily I was wearing lots of eye protection at the time but I did have a few steel wires sticking in me about an 1/8th of an inch or more. I
ts like acupuncture that you never signed up for. DO NOT USE THEM only use braided wire brushes and make sure you have not only safety glasses but back that up with a face shield. You really need to do this.. there are no other options. Also wear protective clothing. A thin shirt is not going to cut it.
Ok so now you are ready to start grinding and you can back that up with hand brushes and sand paper where the grinder won’t reach. Remember to also wear a dust mask and don’t use the crappy 10 for $1 ones get some good ones or get a respirator type mask that is made for dust.
If you have any weak spots in the metal or holes you will need to get a patch welded in or you may even need to replace the deck but unless you have been letting this go for many years you should be fine to paint.
Once all of the rust is removed you will need to treat the metal with a metal prep and rust converter. This will convert any rust you missed to a neutralized material and it will prep the bare metal for primer.
Honestly this is not an endorsement but the best product I have found for this is SEM’s RustMort. There may be better products out there but I have been using this for decades and it just seems to work well for me. Other people rely on Navel Jelly or other products of the type. They are also ok but a more liquid formula is what works best for me.
Clean the surface with a moist cloth to remove the rust and paint dust then after drying you can apply the treatment. If you have any pitted areas make sure the treatment gets deep into those areas. Allow it to fully dry as directed.
Some products then say to wipe the surface to remove residue.
Once completely dry you can begin taping off everything you don’t want paint on. Newspaper works well for this and you can tuck it behind metal guards and wrap it around your drive belt. Use as little actual tape as you can.
Painting with spray paint doesn’t require as stringent filtration as auto body paint but wear a mask if you have one or at the least wear a heavy dust mask and make sure the wind is blowing away from you.
We will first apply a heavy coat of self etching primer. Unlike a primer surfacer that you use in the last step of auto body painting this type of primer does best on bare metal.
Allow the primer to dry completely before continuing. Normally you do not sand self etching primer but if you have a large run or heavy buildup you might want to remove it.
Normally with primer I find it best to allow the paint to dry longer than directed. If they state 20 minutes to touch and 1hr to paint in 70F weather I will give it longer.. maybe twice the time or even overnight if its cool out.. so there are no problems with the final enamel color coat.
Finally you can apply the final surface paint. I like to use Engine Enamel for any type of spray painting. It is better rated because it is suppose to handle temperature changes and chemicals found on automotive engines. Since the bottom of your lawn mower will see some heavy abuse you don’t want to go with dollar a can paint or it won’t last a season.
Once the top coat of paint has dried to touch you can begin removing your paper and tape. A good way to know if the paint is dry is to spray some paint on the tape as you work then you can touch the tape and not your work area to test for curing.
If you have the time and the need this would be a good time to sharpen and balance your lawnmower blade and then paint it. Once it has dried you can begin the reassembly.
While your blade is drying you can clean up the overspray on your drive belt or other areas by dampening a paper towel with brake cleaner or carburetor cleaner or in absence of that a little gasoline.
Just dampen the cloth not wet or dripping and wipe down the overspray. Make sure you don’t get any on the painted areas.
Final Note
Restoring your lawnmower requires a little work and some basic tools but if you do this when needed you can extend the life of your lawnmower by many years.
You should also find that the painted surface allows grass to flow better either into your bag or out the discharge chute.
And the best thing is grass won’t stick to the painted areas as easy so cleanup should be quicker.
Total cost for this job might run you about $25 if you need to buy a grinder which I really suggest.
I also remind you to wear eye and breathing protection while working.