title = "Shot Blasting and Grit Blasting Surface Preparation"

content = """
Shot blasting and grit blasting are mechanical surface preparation methods used at Ridgecrest Metalworks to clean metal substrates and create a surface profile suitable for coating adhesion. Both processes propel abrasive media at high velocity against the workpiece, removing rust, mill scale, weld spatter, and old coatings.

Shot blasting uses spherical steel shot as media. The rounded shot peens the surface, producing a relatively smooth anchor profile. This method is preferred for components that will receive powder coat or thin-film liquid paint, and is also used to induce compressive residual stress in load-bearing parts (shot peening). Cabinet-type shot blast machines or continuous pass conveyor blasters are used for production volumes. Shot size is selected based on desired profile depth; S-110 to S-330 shot are common.

Grit blasting uses angular abrasive media — crushed steel grit, aluminum oxide, or garnet — which cuts into the surface and creates a sharper, more angular anchor profile. Angular profiles improve mechanical keying for thick epoxy and thermal spray coatings. Steel grit (G-25 to G-50) is standard for structural steel; aluminum oxide is used on stainless steel or aluminum to avoid ferrous contamination.

Blast standards define the cleanliness and profile requirements:
- Sa 1 (Light blast): Removes loose rust and scale
- Sa 2 (Commercial blast): Removes most contaminants; suitable for low-performance coatings
- Sa 2.5 (Near-white blast): Removes all but faint staining; required for most industrial coatings
- Sa 3 (White metal blast): Completely clean; required for immersion or severe environments

Surface profile depth is measured using Testex Press-O-Film replica tape or a surface profilometer. Typical profile specifications range from 40–75 microns Rz for standard coatings and 75–125 microns for thermal spray.

After blasting, parts must be primed within four hours to prevent flash rust, particularly in humid conditions. Spent abrasive is collected, screened for fines, and recycled. Contaminated or undersized abrasive is discarded. Dust collection systems are mandatory to protect operators and maintain air quality. Operators wear air-fed blast helmets, hearing protection, and protective leather gloves during manual blasting operations.
"""

version = "0.0.1"
