Yes. All surfaces need to be thoroughly cleaned before using Saltguard or Saltguard WB. Any staining or soiling on the surface can prevent Saltguard from properly penetrating the substrate.
We recommend using Cleaner/Degreaser to remove general grime, and Oil & Grease Stain Remover for more deeply set stains. For more specific stains like efflorescence or rust that will be removed by professionals, we recommend Light Duty Concrete Cleaner. A clean surface will maximize the performance of Saltguard and Saltguard WB.
Here's a quick how-to video for using Oil & Grease Stain Remover. https://www.youtube.com/watch?v=q9obVHG9o-U&feature=youtu.be
As always, we are here to answer any questions you have. Call us at 1-800-255-4255, Monday through Friday, 8 a.m.-5 p.m., Central Standard Time.