Glossary

A standardized spring steel test coupon (SAE 1070) clamped to an Almen gauge and used to measure shot peening intensity. The arc height the strip takes on after peening — measured in thousandths of an inch — quantifies the energy transferred by the media stream.

The peak-to-valley roughness pattern created on a substrate by abrasive blasting. This micro-texture provides the mechanical "anchor" that allows protective coatings to grip the surface. Also called surface profile or blast profile.

Media with sharp, irregular edges — such as steel grit or garnet — that cuts into the surface to remove scale and produce an aggressive, jagged profile. Contrasted with round shot media that peens rather than cuts.

The manufacturing process in which molten steel is broken into fine droplets that solidify into spherical particles. Macloid Metalix uses controlled water atomization to produce consistent, dense steel shot feedstock.

The footprint of abrasive impact produced by a nozzle or blast wheel on the work surface. Even, overlapping patterns are essential for uniform cleaning and consistent anchor profile.

The rate at which abrasive particles fracture and wear during use, generating fines that must be classified out. Low breakdown rates — a strength of quality steel shot — extend media life and reduce dust generation.

A measure of ion contamination in abrasive media, particularly relevant for coatings on offshore and marine structures. High conductivity from chloride or sulfate contamination can accelerate under-film corrosion.

In peening, the percentage of a surface that has been visibly dimpled by media impacts. 100% coverage means the original surface texture is fully obliterated. Values above 100% (e.g. 200%) denote multiples of the time to reach full coverage.

Abrasive made by cutting drawn wire (carbon or stainless steel) into cylindrical lengths roughly equal to the wire diameter. Cut wire is exceptionally durable, has no internal voids, and is favoured for peening and high-cycle blasting.

Removal of mill scale, rust and oxide layers from steel using abrasive blasting, pickling or mechanical means, exposing clean bare metal for further processing or coating.

Removal of sharp edges, flash and burrs left by machining, casting or stamping, using tumbling, blasting or brushing media to leave a safe, finished edge.

Angular crushed steel abrasive used where cutting action and an aggressive, sharp anchor profile are required — for example, before high-build or epoxy coatings on structural steel.

Resistance of the abrasive to indentation, measured on the Rockwell C scale (HRC) or B scale (HRB). Standard steel shot is 40–51 HRC; hard shot/grit runs 55–65 HRC. Media hardness should typically exceed the workpiece hardness.

The kinetic energy delivered to a surface during shot peening, quantified by Almen arc height at saturation. Specified as an Almen value (e.g. 0.012A) and controlled via media size, velocity and flow rate.

The blue-grey layer of iron oxides that forms on hot-rolled steel during manufacture. It is brittle, poorly adherent and must be removed before coating to prevent under-film corrosion and disbonding.

The generic term for abrasive particles used in blasting operations — including steel shot, grit, cut wire, glass beads, garnet and other materials.

The equilibrium size distribution of abrasive circulating in a working blast machine — a blend of new, partially worn and nearly spent particles. A stable operating mix delivers consistent profile and is maintained by regular addition of fresh media.

A cold-working process in which round media bombard a metal surface, inducing a layer of compressive residual stress that dramatically improves fatigue life and resistance to stress-corrosion cracking.

The arithmetic mean deviation of the surface profile from its mean line. A general roughness indicator, but less informative than peak-to-valley measures (Rz) for coating anchor profile specifications.

The average of the largest peak-to-valley heights over several sampling lengths. Rz correlates better than Ra with anchor profile and is the parameter most coating specifications cite.

Cleanliness grades for abrasive-blasted steel: Sa 1 (light blast), Sa 2 (commercial blast), Sa 2.5 (near-white metal) and Sa 3 (white metal). Sa 2.5 is the most commonly specified grade for high-performance coatings.

The SAE standard defining chemical composition, hardness, microstructure and size designations (S-numbers) for cast steel shot used in blast cleaning and peening.

The SAE standard establishing cast shot and grit size numbers and the sieve ranges each designation must meet, ensuring interchangeable sizing between suppliers worldwide.

A quality-control test that passes a sample through a stack of graded screens to verify that the abrasive size distribution conforms to its SAE designation. Performed on every production batch at Macloid Metalix.

The process of propelling steel shot or grit at a surface using centrifugal blast wheels or compressed air nozzles to clean, descale or profile the substrate.

A controlled process of bombarding metal surfaces with round shot to induce compressive residual stress. Used extensively in aerospace, automotive and spring manufacturing to improve fatigue life.

See Anchor Profile — the height and density of peaks and valleys imparted by blasting, expressed in microns or mils and matched to coating film thickness requirements.

A mass-finishing process where parts and media rotate together in a barrel or vibratory bowl to deburr, clean or polish surfaces without directed blasting.

The most stringent cleanliness grade (ISO 8501-1 Sa 3 / SSPC-SP 5) requiring complete removal of all visible scale, rust and coatings, leaving a uniform metallic colour. Specified for immersion service and high-temperature coatings.

A throwing process in which a high-speed bladed wheel hurls abrasive at the work by centrifugal force. Efficient and dust-low, it is the dominant method for steel media in production environments.

The increase in surface hardness and strength of a metal caused by plastic deformation, such as the cold working produced by shot peening or aggressive blasting.