Pin hole issues on Diamond Cut rims

Due to the many questions, we receive regarding pin holes in diamond cut rims we have made the following post.

Pin holes can be divided between 2 causes: porosity of the aluminium (outgassing) and insufficient cleaning. Outgassing looks like a moon crater, pinholes look like someone put in a needle into the clearcoat.

First some additional information on the rims.

Rims may be manufactured in a variety of ways. Two of the most popular manufacturing processes are “cast” and “forged” rims. Each type is manufactured in a different manner and associated with different advantages and disadvantages.

Process of Manufacturing Cast Rims

The casting process involves pouring or using a vacuum to insert molten aluminium into a mold that is formed into the shape of the wheel in different dimensions. Positive pressure is used to move the aluminium alloys into the mold more quickly and to achieve a product that has a greater density than a gravity cast wheel. It’s allowed to cool. Then, minor modifications are made into the wheel, such as drilling and trimming. This manufacturing process is preferred over others because it’s fast and inexpensive. It’s also less complicated than other processes.

Advantages of Cast Rims

Cast rims offer a good value for a tire while also maintaining strength and a lighter weight. They are easier to make, so the cost savings are often passed on to the buyer.

Disadvantages of Cast Rims

Allowing the molten aluminium to solidify can result in inconsistencies that can cause cracking and oxidation in the wheel. The wheel’s structural integrity can be reduced through this manufacturing process. The rims may be made heavier to compensate for this potential problem.

Process of Manufacturing Forged Rims

Forged rims begin as a solid piece of metal that is then exposed to heat and intense pressure that compresses the material. This material is forged into different dimensions based on the wheel design. In contrast to casting, a forged wheel begins as a solid piece of metal referred to as a “billet.” This billet is then subjected to heat and intense pressure, which compresses the material to form a raw forging. These raw forgings are “forged” into different profiles to allow for the creation of different wheel designs.

Advantages of Forged Rims

Forged rims are less porous than cast rims because of the forging process. The forging process makes these rims stronger, more durable, and more resistant to corrosion and oxidation. Additionally, the wheel’s structural integrity is not compromised. Forged rims tend to have greater overall vehicle performance and enhanced fuel efficiency.

Disadvantages of Forged Rims

Forging is a more time-consuming and precise process. This makes the process more expensive, making the rims more expensive to consumers. Cast rims can be quality rims, so some consumers may not be willing to pay the higher price point demanded of forged rims. However, forged ones offer an incomparable value to consumers.

1.       Porosity of the aluminium rims (outgassing)

As mentioned above there are many different types of alloys and qualities, depending on the manufacturer. It also depends on if the rims are forged or cast. Forged rims are less porous than cast rims because of the forging process. Pinholes is due to out-gassing during the final processing of the rims. It can be solved by preheating the rim to 80 degrees Celsius to eliminate the trapped air. Alternative is to apply several layers of clearcoat to close the pinholes. Make sure the flash-off times of the paint manufacturer between each coat are respected to avoid the clearcoat getting matt once dry.

2.       Insufficient cleaning (pin holes)

Pinholes are usually the result of insufficient cleaning, dirty airlines, or cross contamination.

Insufficient cleaning could be due to usage of dirty cloths, wrong degreaser, remaining dirt/tyre shine/oil on the rim or wrong method of degreasing. Make sure you always use 2 cloths; 1 to solve the dirt (Never let the degreaser completely dry out!), 2^nd to remove the dirt.

Dirty airlines can be avoided by putting an oil-water separator at the end of the airline which separates all the moisture and water from the clean air.

Cross contamination can be caused in the surrounding area. Think about clean hands and clothes (wear gloves and a paint suit) and don’t use silicon containing products in the area (even wind can blow it into the spray zone).

Some tips:

1.       Clean the rim well after preparing the rim for paint with a silicon remover.

2.       Wear nitril gloves during the cleaning process.

3.       Degrease the rim before the Diamond cut process and don’t touch it with bare hands afterwards.