The battered brake calipers that look like they have been used are repainted with a gun coat that does not lose to the brake fluid!

Many Sunday mechanics have had the experience of spray-painting brake calipers and master cylinders that have lost their paint over time with lacquer spray to cover up the rust, only to find that they look terrible and disappointing. I'm sure there must be many Sunday mechanics who have experienced this. Brake fluid has the property of damaging the paint, so once it gets on the painted surface, it must be washed off with water as soon as possible. So what is the best way to refresh tattered calipers?　It is no exaggeration to say that "gun coat" is the only choice if you expect a reliable finish.

Brake fluid that easily dissolves urethane paint as well as lacquer spray.

A brake caliper whose paint has deteriorated to the point of looking as if it had been left on the beach. The rusted brake banjos and banjo bolts clearly indicate that the car was stored in poor conditions.

It is fortunate that the slide pin (a rod-like part with plating), which is the key to the pin slide caliper, is not rusted. If this pin is corroded and rattles when the caliper is set, brake feel will deteriorate.

Many DIY motorcycle riders know that brake fluid used in motorcycle and automobile disc brakes (and drum brakes in automobiles) can damage the paint. Some may not realize that when they change the brake fluid, the fluid that has popped out of the master cylinder reservoir tank has gotten on the gas tank, and before they know it, they are shocked to find stains or, even worse, peeling paint. The reason brake fluid damages the paint in the first place is because the main ingredients, glycol ether and polyalkylene glycol, are incompatible with the paint. They are ideal as hydraulic fluid for hydraulic brakes and clutches because of their low viscosity and high fluidity, and they do not boil or oxidize easily even at temperatures above 200°C. On the other hand, their high polarity makes them easily penetrate the minute crevices in the paint film. However, it is the "glycol-based" fluids such as DOT3 and DOT4, which are in the majority, that damage the paint, while the "silicone-based" DOT5, which is in the minority, is not so aggressive. If that is the case, it may seem like it would be a good idea to put DOT5 fluid in brakes that use DOT3 or DOT4 fluid, but glycol-based and silicone-based fluids are not interchangeable because the rubber used in the piston seals and dust seals has different properties and is not interchangeable. When glycol-based brake fluid adhering to painted surfaces penetrates into the cracks of the paint film, it penetrates between the resin molecules that are the base of the paint and causes it to swell. When a stripper is applied, the painted surface shrinks, wrinkles, and lifts up, and brake fluid has a similar function. Therefore, when brake fluid adheres to urethane or lacquer paint, which is commonly used to paint exterior parts, it must be washed away with running water before it penetrates the paint film. It is important to wash it off with water, because a wet rag or a dry rag may seem to wipe it off, but it may end up spreading the paint.

Guncoat is a functional paint that will not peel off even with brake fluid.

Carbec, Tokai, Aichi, is the authorized exclusive distributor of KG, which manufactures Guncoat, and stocks as many as 70 color variations, which can be purchased immediately via its online store. Capacities come in three sizes (500cc, 1000cc, and 1 gallon), and prices vary by color.

The reason why the paint peels off when brake fluid adheres to the cowl and gasoline tank, but not easily when it adheres to the brake calipers and master cylinder, is because the paint used around the brakes has different properties than lacquer or urethane. Most brake parts installed on commercial vehicles are coated with paints made of epoxy or polyester resins that are baked and cured at high temperatures. These resins are highly resistant to glycol ethers and polyalkylene glycols, which are components of brake fluid, and will not easily swell or peel off. This is due to the chemical properties and design of the paint. Therefore, baking and drying lacquer or urethane paints at high temperatures will not provide resistance to brake fluid. On the contrary, exposing them to temperatures close to 200°C will cause the resin to deteriorate. Such brake paints can also fall apart when they begin to peel off over time. Even if it is repainted with lacquer or urethane paint, it will peel off easily if brake fluid adheres to it. The most reliable solution in such situations is gun coat, a functional paint. Developed for the purpose of coating firearms, which become extremely hot when firing bullets and shells, GUNKOTE has the features of "high heat dissipation," "high surface hardness," and "high chemical resistance. Regarding chemical resistance, the coating film remains unchanged even when immersed in gasoline, thinner, isopropyl alcohol (an organic solvent), acetone, or brake fluid. This performance is possible only because GUNKOTE was designed to achieve such characteristics. While there may be other paints with similar performance, Carbecue, the exclusive distributor of GUNCOAT, always has nearly 70 color variations in stock, with the added benefit of easy availability through the company's online store.

Paint can be applied directly to sandblasted parts.

When sandblasting to remove paint, mask off areas that will not be subjected to abrasive.

Paint stripping is completed in a matter of minutes because the paint is so damaged and the sandblasting is so powerful. This sandblasting cabinet is also an original Kerbeck product.

The fine particles of the sandblast completely stripped the paint, even in narrow areas that could not be reached with a stripper and brush.

The same is true for gun coats, where surface preparation is critical for a good paint finish. Dirt and oil can cause poor bounce and adhesion, and in the case of gun coats that are baked-dried, it is essential that the old paint be stripped off, as the high temperatures can cause bad results. In this case, a stripping agent can be applied and brushed off, but at Kerbeck, where the construction was photographed, sandblasting was used for stripping and cleaning. When urethane coating is applied to exterior parts, primer or surfacer is generally applied to the bare surface of the part. However, gun coat requires a spray gun and an air compressor because spray coating is a general rule. A dryer is also essential for baking coating.

Baking and drying at 170°C for one hour or more completes a strong coating that is not damaged by brake fluid.

The specified aperture of the spray gun used for painting with gun coat is 0.4φ, which is considerably smaller than the 1.0φ used in normal sheet metal painting. The trick is to use a small-diameter gun to apply the coating.

If the part is small in size, it is easy to find the leftover paint by spraying while turning the part itself in a circular motion.

Instead of heating pinpoints with a heat gun, the parts themselves are heated in a dryer to a temperature of 170°C. Kerbeck also develops and sells its own heating dryers.

Although gun coats dry at room temperature, baking and drying at 170°C for one hour or more is essential to obtain the unique properties of gun coats such as "high heat dissipation," "high surface hardness," and "high chemical resistance. This is a prerequisite when designing coatings, so it does not mean that equivalent performance can be obtained by baking at 100°C for 3 hours. For a privateer, this bake-drying will be the highest hurdle. Although some heat guns have products that can set temperatures of 200°C or higher, localized heating will not provide average paint film performance. Rather, parts as small as the brake calipers shown here can be baked by diverting a toaster oven with temperature settings. Carbec also sells a small dryer that can be placed on a tabletop. Functionality is definitely the priority for brake parts, and it is important that brake pads have enough remaining capacity and that the pistons operate smoothly, even if they look ragged. However, it is hard to get excited about a bike that you love to ride if its parts look too shabby. If you are going to repaint your bike, and you want it to be as chemical resistant and durable as brake fluid, then you should choose GUNKOTE as your paint of choice.

The brake calipers have been transformed from crusty and peeling to a textured bright brass (gold). The brake calipers will not stain or fade when soaked in brake fluid, so this beauty can be maintained for a long time.