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Discussion Starter · #1 ·
I’ve been looking for a Honda HR21. I’ve seen just two of them for sale locally and they both have the same problem- the aluminum desk is corroded thru toward the back end. The affected area is the vertical wall of the grass chute area and some of the horizontal surface next to the drive belt cover. One mower looked like it had a fairly tough life and the hole was huge on that one (maybe 6-8 sqin) so that clippings were being blown into the belt housing. The other one seemed very well cared for and the hole was maybe 2-3 sqin. My question is – do they all rot away like this or is there some chance of finding a solid one if I’m patient enough? And, is there any good solution to do a repair on it? Thanks!
 

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It is a pretty common problem with these mowers. I used to work at a John Deere dealer who's service dept. also accepted walk behind equipment, and everyone of these model Honda's always had the same type of corrosion & rust.

As 2 cycled fruitcake mentioned, you could most likely have a welder patch it up.
 

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I'm not sure how an alloy deck can "rust". Aluminum welding might get expensive. I'd ask around before committing to purchase a mower and finding out that the welding is too expensive to make it worth it.
 

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There should be some good solid ones out there but in villages in rural Missouri farm country aluminum welding costs only a few dollars extra. Community colleges in the area have welding classes and will do work for peanuts when school is in session.

Not the same model but my Honda HR215 is showing early signs of corrosion on the back vertical wall. So far it's just a few patches of white surface discoloration with no real metal damage. It's starting on the outside, not from underneath the deck. The original owner had the bag but said he used this only for mulching so I thought the flap being down all the time may have contributed to the corrosion.

Suggestions for stopping the corrosion? I thought I'd use an aluminum-safe metal polish followed by car wax. Overall the mower looks great but I need to touch up a few spots on that black flap. I haven't even washed this mower yet.

 

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Lawn Mower Fan
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Can you guys post pictures of the area of corrosion? I must not be familiar with this; I've not seen any on my HR215.
 

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Sorry, my camera's messed up at the moment. I set it for hires macro a couple of days ago and it hasn't worked right since. I just reset it to full factory default and now I have to figure out how to get it set back the way I had it for routine pictures.

Basically aluminum "rusts" like any other metal but aluminum oxide is a whitish grayish color that doesn't look like ordinary (iron) rust. The fact that my HR215 is painted a light silver color that looks like aluminum doesn't help. The paint on that vertical wall under the flap is partially gone and the exposed aluminum is what's oxidizing/rusting.

http://www.ehow.com/how_4548139_aluminum-oxidation-removal.html

Looks like polish then wax is one way to go -- I'd like to avoid acid.

http://forums.iboats.com/showthread.php?t=290208
 

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Part original paint, part peeled paint exposing bare aluminum, part corrosion.
 

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Discussion Starter · #9 ·
Thanks for the ideas guys, but to clarify, the issue is not surface corrosion, not a cosmetic issue, not a matter that will be addressed by a mild acid treatment, polish and wax, or paint. The issue is big gaping holes in the cast aluminum deck that grow from underside out, caused by serious corrosion that threatens structural integrity. Seems that maybe it's not that common. Maybe it’s just a regional thing here in the NW where the choice in growing season is to either cut wet grass or not cut at all. If I see another rotted deck I'll take pictures and post.
 

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It's very easy to crack or knock a hole in an aluminum deck. Most Lawnboy holes I've seen have been on the side but with a Honda they may be more common on the back. I don't know if stones are more likely to go one direction than another or some parts of the deck are just weaker. Some people continue to use a mower with a hole in the deck but once the hole is there corrosion spreads fairly rapidly. It could be chicken or egg, that the hole came before the corrosion.

It may be regional but more due to gravel in the soil rather than wet grass. In Missouri south of the prairie in rocky hilly forest country even dumping a foot of black dirt around a new house or starting with thick sod sooner or later rain brings gravel to the surface. It's impossible to find every pebble and stone unless you crawl along feeling with your fingers. I hear a couple of dings from small rocks hitting the deck every time I mow. The blade doesn't have to hit a rock -- vacuum lift alone can fling one hard enough to do some real damage. That's the main reason I'm leery of aluminum decks.
 

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Discussion Starter · #11 ·
Definitely not rock damage. I’ve seen holes knocked thru LBs and in Hondas too. Knock outs are different based on location, shape and tendency to grow from small perforations to huge gaping voids. This is corrosion damage.
 

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corrosion like that, indicates some kind of electrolysis due to probably phosphates in the soil, or whatever the lawn is fertilized with& if the water(rain or faucet)is "hard"natural minerals can erode any metal. most cast decks were cast aluminum, some magnesium alloy.
also possible when it was built, the paint&primer just leach out solvents over time&it corrodes the deck. do you live near any power plants that burn coal or oil? the exhaust from those places are loaded with corrosive particles that settle everywhere. i.e black streaks on a roof, &that usually means the crud settles into the grass&ground.
 

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to cure the rot i'd wash the corroded areas with pure baking soda, then fill holes etc...
 

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I bought this about three weeks ago for $10. I know nothing of its history except I was told it was one owner and always garaged. It's always started with one pull and after I cleaned the carb it runs fine.

corrosion like that, indicates some kind of electrolysis due to probably phosphates in the soil, or whatever the lawn is fertilized with& if the water(rain or faucet)is "hard"natural minerals can erode any metal.
do you live near any power plants that burn coal or oil?
I thought it might be fertilizer myself but there's no corrosion under the deck. Water is very hard in this area but few people ever water their lawns. In fact, I don't I've ever seen anyone watering a lawn and I've lived here about 40 years. No power plants. No industry. The area is sparsely populated -- only 4,000 people in the whole county -- no hospital, one Walmart and two grocery stores.

to cure the rot i'd wash the corroded areas with pure baking soda, then fill holes etc...
Okay, baking soda can't hurt so I just did that. There are no holes, just some roughness and faint pitting that could be filled with wax or paint. I don't have much luck painting things especially with rattle cans. I'll probably just wax it. I'm never going to use it anyway.
 

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Discussion Starter · #15 ·
I ended up buying one that I had previously seen- the one with less damage. Here are pictures of the deck holes. As you can see, not in places where damage would be caused by thrown debris.
 

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Aluminum is the metal of choice because of it's resistance to corrosion and stiffness. It is not corrosion proof as shown in your pics. Some of those parts look like rusted steel though I cannot really tell. Aluminum doesn't rust but is does corrode. Aluminum is kinda self healing because it forms a coating that stops corrosion....That is until something blasts it off again like would happen in the chute area of a lawnmower. In the case of you mower I would guess that continuous yearly exposure to wet fertilized grass clippings set the stage for this corrosion. Fertilizer laden clippings may have collected on the top of the deck as is often the case and just sat there corroding away. One thing you can say. If that was a steel deck the mower would be far worse than it is now.
 

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I remember seeing this ad on TV in fact I think there was a hour long show once. They could build up a broken part grind it flat drill and tap it and reuse the broken part. check out the link and there`s a video on you tub. It` all done with a propane touch and these thick sticks of aluminum, just like brazing. They even fixed a hole or tear in a aluminum boat.

http://durafix.com/
 

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Never saw aluminum corrosion look like that before. Looks like steel like rdaystrom mentioned.
 
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