Dustless Blasting is an amazing process which is faster, cleaner, and more economical than traditional dry abrasive blasting. The water in the Dustless process can promote rust, but we can easily prevent this by using the Dustless Blasting Rust Inhibitor.
Not only does proper use of the Rust Inhibitor prevent oxidation, but it also leaves a perfect paint or primer ready surface. Rust Inhibitor does what it does not by coating the metal with a rust proof barrier, but by completely removing chlorides from the metal. As long as you don't recontaminate the metal you'll be rust free for up to 72 hours.
Rust inhibitor needs to be mixed with the blast water in a 1/100 ratio, which is about 7 oz for every 5 gallons. This prevents chlorides from being embedded into the metal during blasting, but after blasting is complete you still need to give it a final rinse. We like to use a fertilizer sprayer that screws onto a water hose and measures out the selected amount of rust inhibitor per gallon. The one we've used in the video is available at Home Depot.
An even easier solution if you own one of our mobile units is to add the rust inhibitor into the water tank, and rinse the metal with our super-fast water pump and a hose. After the rinse down it’s important to make sure all the standing water is removed from the metal, so that it can air dry. We use an electric leaf blower for this. As long as nothing recontaminates the metal (water, dew, body oils, etc.) rust will stay away for up to 72 hours. It is a good idea to try to prime the metal as soon as possible after blasting.
Using well water or hard water can affect how well the inhibitor works. You can combat this by adding more rust inhibitor, or filling up your tank elsewhere, with softer water.
You also have to consider what's happening to the steel when you blast it. Angular abrasives, like glass, strip like a champ and leave a great anchor profile for a new finish. But creating those peaks and valleys also opens pores in the metal exposing it to way more oxygen. Then, even the humidity in the air alone can contaminate the surface causing it to flash rust, despite using an inhibitor in your blast water. If the inhibitor isn't enough to stop it at the iron, you can control it by using a round abrasive so you're not exposing the metal to so much oxygen.
If you're working on a larger project, you should rinse it with inhibitor every so often. The media sitting there on the metal can leave spots and flash rust.
Refer to the chart below to find out how much rust inhibitor you should use.