In the Field
Spalling is the reason cheap steel plates kill the people they were supposed to protect. When a high-velocity round hits an uncoated steel plate, the round fragments on impact and the fragments fly somewhere. Without an anti-spall coating, those fragments can travel up the wearer's neck, into the face, or into the armpits and groin where soft armor does not protect. The physics is straightforward and the injury potential is significant. This is why every reputable steel plate is sold with an anti-spall coating and why uncoated military surplus or budget plates are a poor purchase regardless of how good the price looks.
Common Mistake
Buying uncoated steel plates based on price without understanding that spalling fragments can produce injuries to the wearer, including injuries to the face, neck, and other unprotected areas.
Technical Detail
Spalling is the fragmentation of projectile or armor material that occurs when a round strikes certain types of body armor at high velocity. The impact energy fractures the round, the strike face of the armor, or both, sending fragments outward from the impact site.
Spalling by armor type. The risk and behavior of spalling differs significantly by plate material:
Steel plates. The highest spalling risk. When a high-velocity round strikes uncoated steel, the round itself fragments on the hard surface, and the fragments can travel laterally and upward across the plate surface. Without a coating to capture or redirect these fragments, they can exit the armor area and strike the wearer's face, neck, axilla, groin, or extremities, or strike bystanders. Spalling from steel plates is a documented injury mechanism with cases of severe facial and neck injury.
Anti-spall coatings on steel. Modern steel plates are typically coated with a polymer or composite anti-spall material that captures or redirects projectile fragments. The coating adds weight and cost but is essential for safe wear. Steel plates without anti-spall coating are not appropriate for use, even though they may meet ballistic rating requirements when tested without considering spalling.
Ceramic plates. Lower spalling risk for the wearer. Ceramic plates fragment internally when struck, with the fragmentation absorbed within the plate's construction. Some external fragmentation can occur but is typically captured by the plate's encapsulation material.
Polyethylene (UHMWPE) plates. Very low spalling risk. The polyethylene matrix tends to capture and disperse energy without producing significant external fragmentation.
Soft armor. Effectively no spalling. Soft armor captures and decelerates rounds within the panel without producing fragmentation.
Why spalling matters operationally. Spalling produces injuries that are not stopped by the rated armor:
Facial and neck injuries. Fragments traveling upward from a chest plate impact can strike the neck and face, potentially causing significant injury including airway compromise.
Axillary and groin injuries. Fragments traveling laterally can strike unprotected junctional areas, potentially producing junctional hemorrhage in regions the armor was not designed to protect.
Bystander injuries. Fragments can travel beyond the wearer to injure nearby personnel.
Rated armor that produces severe spalling on impact is functionally less protective than rated armor that does not, even when both are stamped with the same NIJ rating, because the rating addresses penetration but not all secondary injury mechanisms.
Procurement implications. For armor procurement:
Steel plates should be specified with anti-spall coating. Procurement documents should explicitly require anti-spall treatment.
Steel plate procurement should consider weight and coating tradeoffs against alternative materials. Modern ceramic and polyethylene options often provide better protection-to-weight ratios than coated steel.
Military surplus and budget steel plates without verified coating should be avoided for active-use deployments.
Plate inspection should include checking for coating damage, which can compromise spall protection over time.
The recognition of spalling risk has been one of the drivers of industry shift away from steel plates toward ceramic and polyethylene options for both military and law enforcement use. Steel plates retain a place in training and budget-constrained applications where the limitations are understood, but their use as primary duty armor has declined substantially.
