doughboy52
Contributor
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- 2013 CX-5 Touring FWD Sky Blue
Anyone have some recommendations on bolts to use on the license plates that won't rust and corrode?
Bolts for license plate that won't rust
- Thread starter doughboy52
- Start date
Metric Thread M6 Stainless Steel Button Head Hex Socket Cap Screws. This size (both diameter and thread) fits the hole that came in the rear door of my CX-5. They are available on ebay in various lengths. I got 25mm length. You will need a set of metric allen wrenches. I think that the socket head cap screws look better than normal screws and they make license plate theft more difficult.
http://www.ebay.com/itm/15pcs-Metric-Thread-M6-Stainless-Steel-Button-Head-Hex-Socket-Cap-Screws-Bolts-/291199780869?pt=LH_DefaultDomain_0&var=&hash=item43ccdc0805
http://www.ebay.com/itm/15pcs-Metric-Thread-M6-Stainless-Steel-Button-Head-Hex-Socket-Cap-Screws-Bolts-/291199780869?pt=LH_DefaultDomain_0&var=&hash=item43ccdc0805
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While stainless steel is corrosion resistant it will eventually rust. Especially if you live anywhere that puts down road salt. I would reccomend trying to find nylon or aluminum bolts. If you use aluminum make sure you put a bit of anti-seize on the threads to prevent galvanic bonding with the threaded part on the car. You could also go with titanium, but those are going to be expensive. Same goes for chrome. If you look on eBay they have some nifty looking aluminum bolts with finishing washers in the M6x1.0 size that could look cool
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There are grades of SS that don't rust but they are very expensive and you probably won't find them at your local hardware store. A good marine store will carry them but be prepared to bend over as you pull your wallet out.
For holding a license plate on the nylon ones are excellent.
doughboy52
Contributor
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- 2013 CX-5 Touring FWD Sky Blue
Lots of great info, and I'm glad a few of you mentioned the M6 x 25mm/1". That's all of the info I was looking for in addition to the recommendations on types of screws. Anyone know if the front ones are different since they screw directly into the bumper cover? I know I could back them out to check, but it's much easier if someone knows offhand 
Chris_Top_Her
Contributor
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- San Antonio, Texas
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- '15 CX-5 Miata AWD
Could spray some clear coat on them or black primer
Every type of stainless steel is susceptible to corrosion and rusting. It's not a matter of if its a matter of when. Even Marine grade SS which is usually SAE-316 will rust under the right conditions. http://en.wikipedia.org/wiki/Marine_grade_stainless If one was going to shell out the money for Marine Grade (316) stainless they might as well get titanium or aluminum which won't rust, ever.
Lots of great info, and I'm glad a few of you mentioned the M6 x 25mm/1". That's all of the info I was looking for in addition to the recommendations on types of screws. Anyone know if the front ones are different since they screw directly into the bumper cover? I know I could back them out to check, but it's much easier if someone knows offhand
I used the same size on front and rear.
Lots of great info, and I'm glad a few of you mentioned the M6 x 25mm/1". That's all of the info I was looking for in addition to the recommendations on types of screws. Anyone know if the front ones are different since they screw directly into the bumper cover? I know I could back them out to check, but it's much easier if someone knows offhand
The front screws are not bolts so they don't have a thread pitch. I don't know what number screws they are using, likely either a #10 or #8 as they are quite beefy. They are just screws that form the "threads" as they are screwed into the divots for the front plates. you might be able to find some plastic or aluminum ones that would work after removing the metal ones.
Even titanium fasteners (and especially aluminum fasteners) are susceptible to corrosion. Titanium, aluminum and SS alloys all get their corrosion resistance from the surface formation of an oxide film. Depending upon the environment, this may not be enough to prevent further corrosion.
As an ex-Alaskan commercial fisherman, I can tell you that #316 stainless steel has more than adequate corrosion resistance to use as a license plate fastener. It is even used for implants within the human body. Aluminum alloys, not so good for license fastening unless it's anodized and even then you might have trouble. Titanium alloys have varying degrees of corrosion resistance, typically more resistant than SS and aluminum alloys but at a cost 2-3 times that of #316 SS. A good choice if you don't mind the cost.
I don't know how long you expect to keep your CX-5. I bought hardware store SS bolts (socket head) to use as license plate bolts for a 2005 Nissan. I kept them when I traded the car and transferred the bolts to a 2009 Ford, and then again to a 2013 Honda that the wife is still driving. The bolts still look like new and don't show signs of corrosion. At this rate those bolts will outlast the car and me.
I know that all metals corrode even aluminum and titanium will corrode but the important thing is what type of corrosion is taking place. Iron, found in all stainless steals, have a destructive corrosion known as furious oxide aka rust. It weakens the metal and it falls apart. Aluminum is more reactive then iron or steels but when it corrodes it's not nearly as destructive. Aluminum corrosion forms aluminum oxide, a ceramic, that gives the chalky white appearance to aluminum. Aluminum oxide actually stops further corrosion of the surface, it forms a somewhat protective layer. The alloying metals that make up stainless steel also form a protective oxide "film" like aluminum. The problem with aluminum arises from galvanic corrosion when it interacts with different metals. Which is why I said a bit of anti seize on the threads would be a good idea. Titanium is very similar and very corrosion resistant and work well for license plate bolts.
I wasn't saying marine grade stainless was a bad choice just that under the right conditions it can rust. Sea water and road de-icing chemicals are two different things. There is more then just sodium and chloride (salt)that they put down on roads.
Bottom line get plastic bolts
I had a few extras left over from my S, so I used them for the plates. A bit short but it does the job.
http://shop.moddiction.com/Moddiction-Titanium-Bling-Bolts-012.htm
http://shop.moddiction.com/Moddiction-Titanium-Bling-Bolts-012.htm
puddle.jumper
Member
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- mazda cx-5 touring 2013
Several weeks ago got some Titanium M6 25mm bolts Torx size T30 on eBay for about $7. I chose the tapered version for a clean and flat-shaped look. It's a matter of preference but there's also the rounded shape head and also a thumb-screw style as other options. The reason I chose torx is some small theft deterence. Although they can still be removed with the right tool as well as some other means, they're not as common as hex in hardware stores for this particular size.
Thanks for the size and other info in this thread. They are awesome.
Thanks for the size and other info in this thread. They are awesome.
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- Plano, Texas, USA
I thought I'm the only one picky on these license plate screws. I'd been trying to order OEM license plate screws from dealer's parts for all the cars we bought. The parts guy normally thought I'm crazy but sometimes they did have those in the parts list. I got 4 OEM stainless screws for rear plate on our VW Passat but after 14 years some of them do show signs of rust.
Dealers normally use Phillips pan head sheet metal screws to screw into the plastic bumper for front license plate. I chose not to put front plate on as it blocks some air flow and creating ugly holes on front bumper.
Dealers normally use Phillips pan head sheet metal screws to screw into the plastic bumper for front license plate. I chose not to put front plate on as it blocks some air flow and creating ugly holes on front bumper.
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