- My model of MX-5 is: c
- I’m based near: Exeter
- I’m looking for technical help or recommendations on: rust treatments and protection.
My mot advisories noted some subframe corrosion and the guy said it needs attention.
What would you recommend for treating the underside of my beloved mx5 so it doesn’t crumble away? Is it Waxoyl or nothing? What are my options?
Most/all NC’s will have some kind of corrosion beneath their beautiful exteriors.
The extent of it will vary, wildly.
I’d recommend getting a hold of Anand Viad on Facebook.
He’s pretty clued up on what to do to address and protect your car up to and including the bits of the chassis you can’t see into that water can get into and cause corrosion.
Well worth the dialogue factor…He’s based in Slough so not sure how far that is from you.
He’s 300 miles from me but I made the trip there and back. I’m a happy MX-5 camper 
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I would second the recommendation for Anand Vaid
Both mine and my brothers MX5’s NA &NC were future proofed by him.
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This is clearly a high quality option. Is it also an expensive one?
Have the job done properly and the cost will pay for itself if you intend to keep your mx5 for a good few years.
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You make an excellent point. So is this an investment of hundreds or thousands?
Bank on a grands worth if it needs no welding…
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An NC so a minimum of eight years old… if not already treated expect to see underside surface rust which will need cleaning up before applying rust proofing.
You need to get the arch liners off and inspect the arch rims for perforations appearing and the quarter panel area (ideally a boroscope inspection here) to see if there is signs of crumbling.
NC subframes can get picked on in MOT tests, they often can be recovered by a good clean up and treatment.
Waxoyl is an old fashioned rust prevention treatment, there are more modern products like Dynax S50, Dynax UB etc and others.
To strip, clean, inspect, treat and allow time to dry should take about a week so be wary of anyone offering a cheap or quick turnaround, you’ll probably get a layer of something sprayed over the top of any emerging problems.
If you have access to suitable facilities it’s not the most difficult DIY job, then you know it’s done well, that or pay a known and recommended professional.
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If you do want a full honest free appraisal then you would have to spend the fuel money to see Anand Vaid when he will advise then what needs to be done and quote you accordingly.
Happy to send you photos when my NA was treated.
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I have a 2009 Sport Tech which is immaculate up top but a different story underneath. Its only done 29k but the last Mot picked up non structural corrosion as an advisory. I booked it in to a local specialist garage for a 3 day £750 Dinitrol treatment but they were honest and said the corrosion spread was too extensive. So, I decided to do it myself. I replaced some rusty bracings and got onto the Dinitrol website where they have kits for different types of vehicles. Preparation is key and its taken me 3 weeks in my garage on my back. Applying the rust converter, underseal and cavity sealant are relatively quick, although you do have to allow time between coats, its the scraping, wire brushing and cleaning that takes the time. At the end of the day the rust, although widespread wasnt deep, a surface layer and i hope I’ve caught it in time, or at least pushed the rust clock back 5 years anyway. My Dinitrol purchases cost in total around £250, the Kit was £150 but I also bought additional converter. You can buy Dinitrol through Amazon but get onto the Dinitrol website to find out what you need and how to apply it. Good luck.
Dave MacPherson
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£750 seems like a lot of money to spend on a car that already started to rust. If you can do it yourself that’s got to be the way to go! This is not a difficult job to do at all and at least doing it yourself you will know it’s done properly.
There is no way of absolutely 100% stopping your MX from rusting unless you get it treated properly when it’s new, don’t drive it in the wet and keep it in a garage. You can slow things down but you will inevitably also be trapping existing rust which will fester eventually.
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A more local option for you might be South West rust Proofing. I had my 17 year old Landcruiser done by them a couple of years ago. Takes 3 days for the process but I’m planning on having it for another 10 years so to me the £900 was worth it. Mx5 would cost less I expect. You can see the work they do on their website.
I’m just at the start of a long renovation project on my mx5 so will be doing it all myself but the landcruiser needed to be up on a lift and I don’t have that sort of gear.
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Yep - South West Rust Proofing did my MX5 NB 2.5. £700 for the Donitrol treatment. Unfortunately they found rusted areas during their prep work - the MX5 looked beautiful before the stripped everything back! Cost me a lot but I wanted to keep it in tip top condition. Cost £2500 in the end including a very professional respray to affected areas. Alas a year later someone wrote it off!!
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Many thanks. I’ve just received my quote. It’s just over £1000.
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Does anyone have experience or thoughts on the undersealing treatment the MX5 Restorer (Eastbourne) offers?
As mentioned by Dave MacPherson, I did a diy job with Dinitrol, I ordered my MX5 kit from Rejel £135 (2 years ago), removed all wheel liners, had it up on axle stands, wire brushed every accessible piece of surface rust, removed all bungs to access sill cavities, if you’ve got a small led torch you can see inside the sill cavities, treat everything with rust prevention, left it to cure, treat all cavities with cavity wax, left it to cure, then covered everything in rustproofing, it’s a time consuming job, but if your not frightened to get your hands dirty and want to save yourself a few quid it’s worth the effort,2 years down the line and it’s still showing no rust, granted I don’t drive it in wet weather but that said it’s still a quality product.
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Thanks. That’s interesting. So my local garage could probably do it even though they’re not a rusty proofing specialist. They actually recommended Waxoyl, but I get the impression dinitrol could be better.
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There’s a lot of divided opinions on which treatment to use, I think Waxoyl’s been around since you used to have a guy walk in front of you with a red flag when you were driving 
, (don’t know how old you are so you might not relate to that) , I’m not doubting that Waxoyl is a good product but it can need thinning out to apply and you can’t access all areas of rust with it, Dinitrol is all aerosols, it’s easy to apply and you can get into all the nooks and crannies with it, any decent garage should be able to do it however I did it myself so I knew it had been done thoroughly, don’t take my opinion as gospel that Dinitrol is the best but if it isn’t it’s right up there with them, also if need be (or in my case not but I’m going to do it anyway) you can just order a tin of rustproofing to top it up if any surface rust does come through, wire brush it first though.
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I bought a 2008 NC with under 11,000 genuine miles on the clock in February 2022. I had the underside treated with Hammerite black wax, Tectyl clear cavity wax and also spray grease on the nuts and bolts as required, at a Derbyshire bodywork specialist. Anyone got any ideas if it was a good move on my part, perhaps compared to other materials?.
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Probably worth getting it up on a ramp to check but it’ll probably be ok for a few years. There’s no one solution for life so it’ll need periodic maintenance anyway.
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