Whether it’s on your car or in a bearing, rust is never a good thing. Corrosion is caused by environmental factors such as water, salt water, acid/alkaline solutions or chemical intrusion.
Most rod ends, ball joints and tie rods are used in outdoor applications, so rust resistance is vital. By preventing rust buildup, machines have a longer life and less maintenance needs.
When it comes to preventing rust, there are a few ways to coat the metal for the longest life possible. Depending on the material, heat treatment and painting, bearings can be coated with a variety of materials:
- Plating
- Zinc
- Nickel
- Chrome
- Tin
- Copper
- Phosphating
- Moly Coating
- E-coating
- Anodizing and
- Powder Painting
Salt spray tests are used to measure the coating protection. The longer a coating can tolerate the test, the better it is for the part. In fact, some of the coatings can meet up to 1,000 hours before rust begins to show.
What is a Salt Spray Test?
Salt spray testing is one of the most widely accepted corrosive-testing measurement tools. It’s used to check corrosion resistance of materials and coatings by accelerating a caustic attack on samples. The results help to evaluate the suitability of the coating as a protective finish. OEMs will generally have a set number of hours that a part or bearing will need to endure in order for the coating to be considered acceptable.
The salt spray machine is a closed chamber where a salt water solution is sprayed onto the bearing using a pressurized nozzle. Inside the chamber, a corrosive environment is produced due to the dense salt water mist.
Testing ends when either white or red rust appears. Red rust means that metal substrate is starting to rust. White means that zinc plating is beginning to rust.