How do you prevent rusting while wet abrasive blasting?

One of the most common question asked by people looking to purchase a dustless blasting machine is ‘How do I prevent steel from getting rusted after wet blasting?

Yes, wet blasting can cause rust due to the water used in the process but it is easily preventable. The solution is quite simple using a Rust Inhibitor. Different rust inhibitors work in different ways. Whilst some removes chlorides from the water others provide an invisible film to the substrate. 

There are over 200 different brands of Rust Inhibitor available in the market. Many coatings will not tolerate them, not all are environmentally friendly, and some are known carcinogens.

Products include

• Holdtight 102

• Blast x 108

• RapidHold Superstrength

The rust inhibitor is simply added to the pressure vessel in the recommended proportion using a dosing unit. Most rust inhibitors are required to be used in a ratio of 1:100 whereas the RapidHold Superstrength rust inhibitor is a concentrated solution requiring only 0.5% dosage and is mixed in a ratio of  1:200.

When the slurry mix contains the right proportion of Rust Inhibitor, after the sandblasting process, the RapidHold Superstrength rust inhibitor forms a non-greasy invisible film on the surface. The film passivates the metal surface and inhibits the formation of superficial fash rusting upto a period of 72hrs and in many cases longer depending on the environmental conditions

Once the blasting is finished, one needs to perform a ‘wash down’ to remove the abrasive media sand and to clean the substrate. It is important to use the rust inhibitor during this process also. Wet abrasive blasters such as the Rapidblast have a built in wash down mode which makes this easy by still using treated water. Other units such as a Dustless Blaster require a separate pressure cleaner.

In the case of aggressive environments such as chemical plants, in coastal areas, or near heavily travelled roads where air pollution is high, it is important to apply protective coatings as soon as possible after the surface is thoroughly cleaned and dried before excessive contamination becomes present on the steel surface.  

RapidHold Superstrength is non poisonous and is not inflammable or a dangerous substance. The application of RapidHold does not affect downstream processing such as painting or powdercoating. In addition to preventing flash rusting, it can also be used in the treatment of metals after acid cleaning, alkaline cleaning or solvent cleaning.

For good rust-prevention and coating adhesion results, follow these best practices:

• Impart the proper anchor pattern.

• Use a good quality rust inhibitor

• Leave the surface as clean as possible.

• Blast in low-humidity conditions.

• Prime as soon as possible.

• Work to the specifications provided by the coating manufacturer.