The Mazda MX-5 NC also suffers from rust problems
It seems that no generation of the Mazda MX-5 escapes it…. Rust. The Mazda MX-5 NA and NB are regularly in our workshop to repair rust on the side screens, sills, wheel wells and chassis beams. With increasing regularity also all this combined, then it soon goes towards a full restoration.
Now we also recently had the first Mazda MX-5 NC in the workshop for a sill/bottom rust repair.
In our instagram post found below, you can see exactly how we tackled this repair.
How and why does rust form on a Mazda MX-5 NC?
Technical explanation:
Rust results from a chemical process known as oxidation, in which iron reacts with water and oxygen to form iron oxide, also known as rust. Here is a simple explanation:
- When iron (as in the body of a car) is exposed to water, a small part of the water dissolves in the iron and forms hydroxide ions.
- These hydroxide ions then combine with iron to form iron hydroxide. This process is accelerated when salt is also present (which is often the case in coastal areas or during winter when salt is spread on roads to melt ice).
- When the iron hydroxide is exposed to more water and oxygen, it is converted into iron oxide hydrate, which we know as rust.
- Rust does not form a protective layer on the iron like some other metal oxides, but instead can continue to form and corrode the underlying metal.
- Over time, this process can affect the metal so severely that it begins to crumble and lose its structural integrity.
In the case of cars, such as the Mazda MX-5 NC, rust can be a serious problem if not addressed early, as it can damage the body and components of the car and even make it unsafe to drive.
Design improvement
The design of the Mazda MX-5 NC has significant improvements over the Mazda MX-5 NA and NB, the previous generations. This results in a reduction of rust incidents in the Mazda MX-5 NC compared to its predecessors.
However, there are certain vulnerabilities in the design of the sill and bottom plate of the Mazda MX-5 NC that can promote rusting:
- At the bottom of the sill, several pieces of sheet metal come together that are spot welded from the factory. Here, several layers of steel stack closely together, making it harder for moisture to escape. This trapped moisture will gradually corrode the material, eventually leading to rusting.
- The part of the sill that connects to the rear wheel well consists of two pieces of sheet metal glued together. Should small gaps develop in this adhesive or sealant layer due to stone chips, moisture can get between these two layers. This moisture, again difficult to get rid of, can also cause rust.
Rust prevention on a Mazda MX-5 NC
Prevention is better (and cheaper) than cure. Therefore, it is crucial to perform regular maintenance and inspect these areas to prevent early rusting. In addition, applying additional rust protection to these vulnerable areas can help extend the life of the Mazda MX-5 NC. Using a cavity wax, anti-scratch coatings and cleaning these areas regularly, especially after exposure to salty air or after driving on roads where salt has been spread, can help keep the car in optimal condition.
Cavity Wax
Cavity wax is a preventive maintenance product used to prevent rust in cars. The wax is applied in the hollow areas of the bodywork, such as the sills, duct beams and doors, which are often prone to rust because they can retain moisture and dirt.
The wax creates a protective, water-repellent layer that shields the metal from water and oxygen, the two elements that promote rusting. It is flexible, allowing it to follow the movements of the vehicle without tearing or flaking off.
A professional application of cavity wax involves injecting the wax into these spaces through specially designed openings to ensure comprehensive coverage. This is a very effective way to extend the life of a vehicle, especially in areas of high precipitation or high humidity, where rust is more likely to form.
It is very important to note that cavity wax should be applied to sheet metal parts that are free of rust. Any rust present should be professionally repaired before applying this coating.
Anti Stone Chip Coating / Anti Stone Chip Coat
Anti-chip coatings are specially designed to protect car bodywork from the damage that can be caused by splashing gravel or small stones. This coating is usually applied to the underside of the car, the wheel wells and the lower parts of doors and bumpers, where the impact of stone chips is greatest.
This protective layer, often made of a mix of rubber and other resins, forms a flexible but tough barrier that absorbs and disperses the force of impact, preventing the underlying metal from being exposed and potentially damaged.
Regularly checking and updating these coatings is important, as they can wear off over time due to constant impact and general weather conditions. A well-maintained anti-scratch coating contributes to both the aesthetics and durability of the car.
Keeping wheel wells and water drains clean
Keeping the water drains in the sills carefully clean is a simple but extremely effective measure. From the factory, several drainage channels are installed in the sill that allow condensation water to drain away. Checking regularly and ensuring that these channels are clear and can drain condensation water can significantly extend the life of the sill.
Cleaning the wheel wells is another simple and effective method of preventing rust. If you feel along the side screen in the wheel well with your hand, you will discover that there is an edge where road dirt and mud can accumulate. During the winter months, this dirt barely dries, which means that this piece of sheet metal is exposed to a humid environment about 4 to 5 months a year. Cleaning this area every time you wash or refuel will significantly reduce the chances of rust.
Repair rusty sheet metal on the Mazda MX-5 NC
If you are late with the preventive (rust) maintenance of your Mazda MX-5 NC and rust has developed, it is crucial to have it repaired promptly and professionally.
Rusting is a relatively slow process, so it can be tempting to put off repairing it until large holes actually appear in the sheet metal. However, in almost all cases it is wiser and more cost-effective to have a repair done immediately at the first signs of rust. Indeed, in many cases the underlying sheet metal is still thick enough to be reused, which can save cost and time.
How LucaCarMods repairs rust on a Mazda MX-5
We begin with an optical inspection of the rust to determine which parts need to be ground out. Here, it is important to strip the material of any coatings so that the underlying sheet metal can be seen. This allows looking at pitting corrosion and sheet metal thickness. We then grind out all rusted and corroded sheet metal parts from the body.
If there is more rust behind the outer layer, we clean it and use a rust converter and primer if the sheet metal still has sufficient thickness. If this is not the case then this will also need to be replaced.
Most importantly, after the repair, there is nowhere to hide underlying rust that can corrode the new sheet metal over time.
Below is an example of a Mazda MX-5 NA where all the underlying sheet metal was also restored.
The way sheet metal is welded into the car is also very important. A simple and quick (inferior) method is a so-called “lap joint”; here you put 2 pieces of sheet metal on top of each other and then weld them together. This method is often used to get the car through the MOT or if the mechanic is not very skilled with the welding machine.
This method is not recommended because at the rear there is overlapping sheet metal where the cavity wax cannot/will not reach but condensation and thus rust can. In places such as the sills below, you won’t escape multiple layers of sheet metal on top of each other but it is advisable to keep this to a minimum where possible.
Welding sheet metal with the “butt joint” method ensures that both the front and back consist of one layer. This makes the chance of rust on the weld seam i.c.w. the use of cavity wax very low.
Applying coatings
All the sheet metal we use during the repair is treated with a weldable primer which ensures that it is well protected from rust from the inside. We then apply another 3M cavity wax after the repair which further minimizes the chance of rust.
We treat all sheet metal parts subject to possible stone chip damage with a 3M Spatter Kit Anti Stone Chip Coating. This is a 2 component coating that is exceptionally robust and matches the original finish from the factory in terms of looks.
Which we then finish with a black 3M Anti Stone Chip Coating.
Make an appointment?
Is your Mazda MX-5 affected by rust and are you looking for professionals who can expertly address this problem? Then don’t hesitate to contact us!
With us, your car is our focus. We understand how important it is to keep your MX-5 in optimal condition. We use our extensive experience and skill to eliminate rust on your car and take preventive measures to prevent future rust.
Contact us today and let’s see together how we can get your MX-5 back in top condition!
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