The Mazda MX-5 NC also suffers from rust issues
It seems no generation of the Mazda MX-5 is immune to it... Rust. The Mazda MX-5 NA and NB are regularly in our workshop for rust repair on the side panels, sills, wheel arches, and chassis rails. With increasing frequency, all of these are combined, quickly leading to a full restoration.
Recently, we also had the first Mazda MX-5 NC in the workshop for a rust repair on the sill/floor.
In our Instagram post 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 is caused by a chemical process known as oxidation, where iron reacts with water and oxygen to form iron oxide, also known as rust. Here's a simple explanation:
- When iron (such as in a car's bodywork) is exposed to water, a small part of the water dissolves into the iron, forming 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 hydrated iron oxide, 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 severely damage the metal, causing it 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 bodywork and components of the car and even make it unsafe to drive.
Design improvement
The design of the Mazda MX-5 NC features significant improvements compared to the Mazda MX-5 NA and NB, its preceding generations. This results in a reduction in the number of rust incidents on the Mazda MX-5 NC compared to its predecessors.
However, there are certain vulnerabilities in the design of the sill and underbody of the Mazda MX-5 NC that can promote rust formation:
- At the bottom of the sill, various pieces of sheet metal come together that are spot-welded from the factory. Here, multiple layers of steel stack closely together, making it harder for moisture to drain away. This trapped moisture will gradually corrode the material, eventually leading to rust formation.
- The part of the sill that connects to the rear wheel arch consists of two pieces of sheet metal that are glued together. If small openings occur in this glue or sealant layer due to stone chips, moisture can get between these two layers. This moisture, which again struggles to escape, can also cause rust.
Rust prevention for a Mazda MX-5 NC
Prevention is better (and cheaper) than cure. It is therefore crucial to perform regular maintenance and inspect these areas to prevent rust formation early on. Additionally, applying extra rust protection to these vulnerable spots can contribute to a longer lifespan for the Mazda MX-5 NC. Using cavity wax, anti-stone chip coatings, and regularly cleaning these areas, especially after exposure to salty air or driving on roads where salt has been spread, can help keep the car in optimal condition.
Hollow Space Wax / Cavity Wax
Cavity wax is a preventive maintenance product used to combat rust formation in cars. The wax is applied to the hollow spaces of the car body, such as sills, box sections, and doors, which are often susceptible 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 rust formation. It is flexible, allowing it to follow the movements of the vehicle without tearing or flaking.
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 lifespan of a vehicle, especially in areas with high precipitation or humidity, where the risk of rust formation is higher.
It is very important to note that cavity wax must be applied to sheet metal parts that are free of rust. Any existing rust should be professionally repaired before applying this coating.
Anti Stone Chip Coating
Anti-stone chip coatings are specially designed to protect car bodywork from damage caused by splashing gravel or small stones. This coating is usually applied to the underside of the car, the wheel arches, and the lower parts of doors and bumpers, where the impact of stone chips is greatest.
This protective layer, often made from a mix of rubber and other resins, forms a flexible but robust barrier that absorbs and disperses the force of impact, thereby preventing the underlying metal from being exposed and potentially damaged.
Regular checking and touching up of these coatings is important, as they can wear down over time due to constant impact and general weather conditions. A well-maintained anti-stone chip coating contributes to both the aesthetics and durability of the car.
Keep wheel arches and water drains clean
Carefully cleaning the water drainage channels in the sills is a simple yet very effective measure. From the factory, various drainage channels are installed in the sills to allow condensate to escape. By regularly checking and ensuring these channels are clear and can drain condensate, the lifespan of the sill can be significantly extended.
Cleaning the wheel arches is another simple and effective method to prevent rust formation. If you run your hand along the side panel inside the wheel arch, you'll find a ridge where road dirt and mud can accumulate. During the winter months, this dirt hardly dries up, meaning this piece of sheet metal is exposed to a damp environment for about 4 to 5 months a year. By cleaning this area with every wash or refuel, the chance of rust will significantly decrease.
Repairing rusted sheet metal on the Mazda MX-5 NC
If you are too late with the preventive (rust) maintenance of your Mazda MX-5 NC and rust has occurred, it is crucial to have it repaired promptly and professionally.
Rust formation is a relatively slow process, which can make it tempting to postpone repairs until large holes appear in the sheet metal. However, in almost all cases, it is wiser and more cost-effective to carry out a repair immediately at the first signs of rust. In many cases, the underlying sheet metal is still thick enough to be reused, which can save costs and time.
How LucaCarMods repairs rust on a Mazda MX-5
We start with a visual inspection of the rust to determine which parts need to be cut out. It is important to remove any coatings from the material to expose the underlying sheet metal. This allows for inspection of pitting corrosion and sheet metal thickness. We then cut out all rusted and corroded sheet metal parts from the bodywork.
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 not, this will also need to be replaced.
The most important thing is that after the repair, there is no underlying rust hidden anywhere that could corrode the new sheet metal over time.
Below is an example of a Mazda MX-5 NA where all underlying sheet metal has also been repaired.
The method of welding sheet metal in the car is also of great importance. A simple and quick (inferior) method is a so-called "lap joint"; here you lay two pieces of sheet metal over 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 back there is overlapping sheet metal where the cavity wax cannot/barely reach, but condensation and thus rust can. In areas such as the sills, you cannot avoid 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 a single layer. This greatly reduces the chance of rust on the weld seam in combination with the use of cavity wax.
Applying coatings
All the sheet metal we use during repair is treated with a weldable primer, which ensures it is well protected against rust from the inside. After the repair, we then apply a 3M cavity wax, which further minimizes the chance of rust.
All sheet metal parts that are subject to potential stone chip damage are treated with a 3M Spatterkit Anti-Stone Chip Coating. This is a 2-component coating that is exceptionally robust and matches the look of the original factory finish.
Which we then finish with a black 3M Anti-Stone Chip Coating.
Make an appointment?
Has your Mazda MX-5 been affected by rust and are you looking for professionals who can skillfully tackle this problem? Don't hesitate to contact us!
With us, your car is central. We understand how important it is to keep your MX-5 in optimal condition. We utilize our extensive experience and expertise to eliminate rust on your car and take preventive measures to prevent future rust formation.
Contact us today and let's work together to get your MX-5 back in top condition!