No plant can afford to have processing lines shut down when inspectors find corrosion or other damage that can result from the cleaning process. Understanding the advanced features now available in washdown-capable gear reducers will help you select the most durable product.
Most washdown gear products are offered with either a cast iron housing covered with an anti-corrosion coating, or stainless steel housing. Although aluminum is thought to be a noncorroding material, when sprayed with harsh chemicals, the aluminum will quickly corrode and fail.
Overall, a coated cast iron housing is the most cost-effective housing option. The cast iron housing is typically the same as used in the standard product line so costs are low due to high volumes. However, the type of anticorrosion coating, and how it is applied, makes a large difference in product performance at the customer’s site.
It’s critical you choose a washdown product from a manufacturer that uses a salt-fog chamber to run corrosion tests. The salt-fog chamber is the most consistent method available to compare the performance of different coatings under the same highly corrosive conditions. Trying new coatings at customer sites may lead to a coating that works well under some conditions, but not in others.
The highest performance coating system currently available consists of two coats of epoxy-based paint applied to the cast iron housing. Epoxy paint has superior adhesion, is highly durable, and offers very high corrosion protection to the base material. Although powder-coated products have an attractive high gloss, salt-fog testing has shown that powder coating does not provide the same level of corrosion protection as the two-part epoxy paint system. Some gear reducers include a clear third layer, but it primarily functions to add gloss for visual enhancement.
For optimal corrosion resistance, look for products that use electrodeposition to apply the first coat of epoxy paint to the bare housing. In the electrodeposition process, a multistep cleaning process is used first to ensure that all foreign material is completely removed from the surfaces being coated.
After cleaning, the part is submerged into a large container of epoxy paint. An electric charge is then applied, which attracts the paint particles into the smallest crevices of the part’s surfaces. The part is then baked to quickly and fully cure the paint. The resulting paint film is very uniform in thickness, extremely durable, and superior to a primer that is applied via a spray system.
After the gear reducer is assembled, it is then completely covered in another layer of two-part epoxy paint that increases the overall paint film thickness to improve the corrosion resistance. A cast iron housing that has been coated with two layers of epoxy paint, with the primer applied using the electrodeposition process, has a better chance of withstanding the harsh cleaning processes required in the food industry.
However, stainless steel housings provide the ultimate in water and chemical resistance. Since no coating is applied to the housing, the coating cannot be chipped off or inadvertently damaged through the use of very high-pressure water. The downside to the stainless housings is the high cost. Despite the cost, stainless housings should be selected when damage to the paint film cannot be tolerated in a particular food production process. For the full story from Baldor's Chuck Russell, visit the website below.