Home
blog
Materials Best Suited for Washdown Environments
Materials Best Suited for Washdown Environments

Materials Best Suited for Washdown Environments

Materials Best Suited for Washdown Environments

In washdown environments, the manufacturing equipment that handles food, beverages, or pharmaceuticals needs to be cleaned by hand or by mechanized means utilizing varying mixtures of water and chemicals. The manufacturers that are involved in these types of applications are required to follow and maintain regulations, standards, and inspections that allow them to safely produce goods and properly maintain equipment.

Within sanitary, washdown, or chemically cleaned environments, engineers must carefully choose materials for bearings, shafting or rails, and seal components to ensure successful performance. A commonly used material in these environments is stainless steel. It is known for its corrosion resistance and durability, and is typically preferred for general use in direct food contact areas. Within this category of stainless steel there are variations in grades, with each grade composed of different levels of chromium and nickel. These stainless steel families are designated by the 300 series and 400 series.

300 Series Stainless Steel

The 300 stainless steel series features relatively soft and non-magnetic properties, and cannot be hardened. It is widely used in food and medical applications and may be varied for different strengths and weaknesses. These adjusted materials are further categorized as stainless steel 303, 304, and 316.

303 (A1 under ISO standards). It has an addition of sulfur and phosphorous making it a free machining version of 304. While it exhibits resistance to corrosion in mild environments, it can be prone to pitting and crevice corrosion within environments that contain chloride and are over 60°C.

304 (A2 under ISO standards). Customers may also know this as 18/8 due to its 18-percent chromium and 8-percent nickel composition. It is the most common grade of stainless steel with excellent forming and welding characteristics. Applications for 304 typically include food processing equipment such as beer brewing, milk processing, and wine making. This is due to its corrosion resistance and excellent ambient and low temperature toughness properties.

316 (A4 or 18/10). This is the most commonly used alloy for applications involved with food and pharmaceutical grades. Its corrosion resistance come from the addition of molybdenum. At a maximum level of 3 percent molybdenum, this alloy can withstand corrosion from industrial chemicals and solvents, making it more resistant than 304.

400 Series Stainless Steel

While there are several types of 400 series stainless steel available, the most commonly used and available class is 440 stainless. It is most often found in cutlery, linear shafting, and applications that require higher wear resistance, mainly because of its ability to be heat treated and hardened. The downsize is that it will oxidize under washdown conditions due to its higher carbon makeup.

Aluminum & Coatings

For engineers interested in using a lightweight aluminum in their washdown environments, components must be coated for protection against pitting and cracking. These protective measures can include anodizing, ceramic coating, or other types of coatings with PTFE or other fillers, but they will not provide the longer life resistance of stainless steel. This factor is what makes stainless steel the preferred material in most caustic chemical washdown environments.

Another popular coating is electroless nickel. These coatings are a common choice mainly because of their corrosion and wear resistance, but also their smooth polished appearance. Some of these forms include a PTFE infusion to aid in non-stick properties, and most are FDA compliant as well.

Non-metal materials such as plastics, polymers, and fillers are increasingly being used inside of mechanical drive components, guides, bearings, fasteners, and more. They are often used because of their lower cost, weight, and ease of manufacturing. The downside is that many solid plastics, such as injection molded bearing inserts, present drawbacks in washdown applications. A common issue includes liquid absorption, which can cause components to swell and subsequently increase the potential for binding and catastrophic failure.

Figure 1 Material