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Discussion Starter #1
Has anyone experience of rust proofing one of these brilliant little cars? I sprayed my Comma Wax Seal under the obvious bits last year but very aware I hadn't the nerve to remove the plastic shield covering the battery, and of course covering some of the critical chassis elements. These parts seem the most rust-prone, as far as I can tell e.g. Jonathon Porterfield's excellent video of a ten year old i-Miev with its really awful rust damage:

So is removing the plastic shield a matter of running it up a ramp and then carefully unbolting the two sections? No need to disconnect the battery etc? Five minute job and then carefully spray waxoyl or the equivalent and an hour later bolt it back on? I can only assume Mitsubishi didn't upgrade their underbody protection since that ten year old i miev hit the road, nor added galvanisation to the treatment etc etc. And if so, the bodywork is the car's most significant weakness, or am I being unduly pessimistic?
 

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The plastic shield can be removed without coming into contact with high voltages - it's basically a stone/water cover to protect the bottom of the battery housing. It's in two parts that overlap and has many bolts to hold it. Here it is removed:

130532


The underside of the battery chassis can get quite rusty, for example:

130533


If you remove the plastic undertray be prepared to replace some of the bolts - they're 6mm bolts of a couple of different lengths and on mine about half of them snapped below the bolt head. :( It took me a good hour or more to drill out the remainder of the bolts and retap the holes with a 6mm tap so I could fit new bolts - not fun!

The biggest problem with removing the plastic undertray to look for and prevent rust is that you're only looking at the bottom of the battery chassis - which is a steel frame which supports the main battery enclosure which is some kind of high strength ABS plastic.

The real rust will be body rust on the underneath of the floor pan and you cannot access that without dropping the traction battery down - which is a lot of work. So a lot of what you're trying to rust proof will be hidden and inaccessible I'm afraid. Mine certainly had a lot more rust on the underneath of the floor pan towards the front and rear ends near the suspension than it did on the bottom of the battery pack chassis. For example:

130534


Not nearly as bad as the one in the video mind you. :oops:

Not well rust proofed cars unfortunately and I suspect they're all like this when they get to this age. (Mine is a 2011) Without removing the traction battery any rust proofing job is going to be half hearted at best, but I'm not sure that the complication of removing it is worth the effort just to apply rust proofing! (I did it to swap some cells and it was big multi-day job)
 

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Discussion Starter #3
The plastic shield can be removed without coming into contact with high voltages - it's basically a stone/water cover to protect the bottom of the battery housing. It's in two parts that overlap and has many bolts to hold it. Here it is removed:

View attachment 130532

The underside of the battery chassis can get quite rusty, for example:

View attachment 130533

If you remove the plastic undertray be prepared to replace some of the bolts - they're 6mm bolts of a couple of different lengths and on mine about half of them snapped below the bolt head. :( It took me a good hour or more to drill out the remainder of the bolts and retap the holes with a 6mm tap so I could fit new bolts - not fun!

The biggest problem with removing the plastic undertray to look for and prevent rust is that you're only looking at the bottom of the battery chassis - which is a steel frame which supports the main battery enclosure which is some kind of high strength ABS plastic.

The real rust will be body rust on the underneath of the floor pan and you cannot access that without dropping the traction battery down - which is a lot of work. So a lot of what you're trying to rust proof will be hidden and inaccessible I'm afraid. Mine certainly had a lot more rust on the underneath of the floor pan towards the front and rear ends near the suspension than it did on the bottom of the battery pack chassis. For example:

View attachment 130534

Not nearly as bad as the one in the video mind you. :oops:

Not well rust proofed cars unfortunately and I suspect they're all like this when they get to this age. (Mine is a 2011) Without removing the traction battery any rust proofing job is going to be half hearted at best, but I'm not sure that the complication of removing it is worth the effort just to apply rust proofing! (I did it to swap some cells and it was big multi-day job)
Thank you so much, Mandrake, for such a comprehensive answer along with such useful photos. You are right that dropping the battery seems a huge task for what I could achieve, and certainly way outside my comfort zone. I was quite happy squirting Waxoyl at my mum's Mini in the 1970s, but didn't expect such poor corrosion protection on a car 45 years later. And even removing the shield seems to be less straightforward, as from what you say, it won't really solve the problem at source, which is what I was hoping, as I hate to see preventable deterioration on such a smart car. Anyway, I guess yours isn't that far gone, and most people here would think the battery is the weak link rather than the bodywork. If only Mitsubishi had made the car in aluminium, as one prototype seemed to suggest, and then we wouldn't be worried (but we'd probably be worried about something else!). Thank you again - it's really appreciated.
 

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You could add front and rear aerodynamic shields and these will prevent stone chipping, mud accumulation and directed winter salt/grit. Should reduce corrosion by a vast amount.
 
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