ESAB Knowledge center.
How do you stop plasma cut parts from rusting?
August 5, 2013
Thermal cutting + mild steel = rust
There are a lot of great reasons to use a water table for plasma cutting. Under water plasma cutting reduces arc glare, eliminates dangerous noise levels, captures smoke, cools the parts, and reduces heat distortion. But one common objection to plasma cutting mild steel on a water table is steel’s propensity to rust. The fact is, freshly cut steel parts will quickly corrode because the metal is bare and unprotected from the environment, regardless of whether they have been cut on a water table or a dry table. But the heat of the cutting process and added humidity above a water table can accelerate the corrosion process, causing hot parts sitting on a water table to rust, and rust fast!
Better living through chemistry
So what can be done to reduce the problem? Nobody wants to add another operation between cutting and finishing. The easy way to address the issue is to prevent the rust from forming in the first place. By using rust inhibiting chemicals in the water table, you can ward off the formation of rust on your cut parts, any remnant plate, and the cutting table itself.
Rust inhibitors create a non-tacky, micro-coating on the metal surfaces. The coating dramatically slows down the rusting, or oxidizing process, providing up to eight weeks of indoor corrosion protection. The protective layer is so minimal, that it doesn't interfere with finishing operations. Parts can be moved immediately to secondary operations, or stored for some period of time.
Further benefits obtained with chemical treatment are protecting the table and slats from rusting and protection of any other surfaces that may get splashed with the table water. That can include the machine's floor mounted rails and drive rack, which can easily get splashed with table water or have water from freshly cut parts or scrap drip on them while unloading the table.
Additionally, water table corrosion inhibitors also prevent foul odors and bacteria growth in the water table. As long as you periodically check the table water and maintain the proper concentration, you will avoid any problems with bacteria and odors. Several chemical mixes also include a dye that helps reduce plasma arc glare.
Maintaining proper balance
Of course, you can’t just put some chemicals in the table once and expect it to work forever. Periodic monitoring of the chemical concentration is required, along with occasional recharging of the table with fresh chemicals.
Some companies suggest monitoring of the pH level or use refractive index to dictate periodic maintenance chemical additions. Chemical Methods, Inc. provides a free chemical test kit to more accurately determine the concentration. Generally, the better the concentration is controlled the better the performance of the inhibitors, extending cut part protection as well as extending the life of the water table.
Clearly there are advantages to using chemicals in your plasma water table. These chemicals can change the table water from a source of problems into a valuable asset to your production process and equipment maintenance.