Vibratory Finishing vs Mirror Polishing: Which Surface Treatment Is Right for Your Hardware?
ZG and LG are not just suffixes on a part number. Vibratory finish (ZG) gives stainless steel a uniform satin texture. Mirror polish (LG) makes it reflective. The choice changes how the part looks, feels, and performs — and it shows up in the price. This guide compares both treatments using real product data so you can make the right call for your next project.
What Is Vibratory Finishing (ZG)?
Vibratory finishing loads parts into a tub with abrasive media and a compound solution. The tub vibrates at high frequency, causing media to rub against every surface. The result is a consistent, non-directional satin texture that removes burrs, smooths edges, and produces a uniform matte-silver appearance.
The process is mechanical and repeatable. No manual polishing is involved. Every unit in a batch comes out with the same texture. For SUS304 stainless steel hardware, this means a clean, industrial look with no visible tool marks or directional lines.
NRH products like the 5101-96-S04-ZG butterfly latch (90 g, 392 N tensile load) and the 5103-63K-S04-ZG spring latch (36 g, 700 N tensile load) use vibratory finish per manufacturer catalog data. The ZG code in the SKU directly indicates this treatment.
What Is Mirror Polishing (LG)?
Mirror polishing takes stainless steel through a multi-step abrasive process — coarse grinding, fine grinding, buffing, and final polishing with compounds. The surface is refined until it achieves a reflective, mirror-like gloss. You can see reflections in it. Light bounces off in a single direction.
This is a labor-intensive process. Each part requires multiple passes with progressively finer abrasives. The final buffing stage uses cotton wheels with polishing compound to bring out the high-gloss shine. The result is a surface roughness (Ra) typically below 0.05 μm.
The 4201-110-0-S04-LG recessed handle (SUS304, 40 kg load) and the 8131-70-0-S04-LG support hinge both feature mirror polish. The LG suffix in the SKU designates this finish per manufacturer catalog data.
Head-to-Head: Vibratory Finish vs Mirror Polish
Appearance & Texture
Vibratory finish produces a satin, matte-silver look. Light scatters in all directions. The surface feels smooth but not slippery — a fine, consistent grain is visible up close. No fingerprints stand out.
Mirror polish produces a high-gloss, chrome-like look. Light reflects sharply. The surface feels slick and glassy. It looks premium but shows every fingerprint, smudge, and water spot.
If appearance consistency across large batches matters, vibratory finish wins. The mechanical process delivers the same texture every time. Mirror polish can show slight variation between operators and polishing runs.
Durability & Scratch Resistance
Satin textures hide scratches. A fine scratch on a vibratory-finished surface blends into the existing grain pattern. The non-directional texture means scratches at any angle are difficult to see.
Mirror polish shows every scratch. A single fine line across a reflective surface is immediately visible. Once the mirror finish is scratched, it cannot be repaired without re-polishing the entire part. This matters in high-traffic applications like military cases, flight cases, and field equipment.
The 5102-88-1-S04-ZG L-type latch (55 kg load) uses vibratory finish specifically for high-wear industrial use. The satin surface maintains its appearance even after repeated handling and tool contact.
Corrosion Resistance
Both finishes start with the same SUS304 base material. The chromium oxide passive layer that provides corrosion resistance forms regardless of surface finish. SUS304 offers the same chemical composition under either treatment.
Mirror polishing does close surface micro-pores more completely. A smoother surface has fewer crevices where chlorides and moisture can collect. In theory, mirror polish offers a marginal advantage in salt-spray performance.
Both ZG and LG finishes on SUS304 pass the same industry-standard salt-spray tests, though. The difference in real-world corrosion resistance is negligible for most applications. What matters more is the environment and the base material grade, not the surface polish.
Fingerprint & Smudge Resistance
This is where vibratory finish has a clear advantage. The satin texture does not show fingerprints. Oils from skin contact absorb into the fine grain and become nearly invisible.
Mirror polish shows every fingerprint. Touch a mirror-polished handle once, and you see a smudge. In medical, laboratory, and food-service environments, this means more frequent cleaning and more visible contamination between cleanings.
For hardware that gets handled frequently — latches, handles, and catches on field equipment — vibratory finish is the practical choice.
Cost & Production Time
Vibratory finishing is an automated batch process. Load the tub, set the timer, and walk away. Cycle times range from 30 minutes to 2 hours depending on part size and media. Labor cost is low. The process also deburrs and edge-breaks parts in the same cycle, eliminating a separate manufacturing step.
Mirror polishing is a manual, multi-step process. Each part requires individual attention through several abrasive stages. Labor cost is significantly higher. Cycle times per part are longer. Reject rates can be higher due to operator inconsistency.
The cost difference between ZG and LG finishes on the same base part can be 20–40% higher for mirror polish. This premium covers the additional labor, consumable abrasives, and quality inspection required to achieve the reflective finish.
Ideal Applications
Vibratory finish (ZG) is the right choice for:
- Military and defense cases — handles frequent handling without showing wear
- Industrial equipment enclosures — hides fingerprints and minor scratches
- Field-deployed hardware — maintains appearance in dirty, outdoor environments
- High-volume production runs — lower cost and faster throughput
- Parts that need deburring — vibratory finish handles both in one step
Mirror polish (LG) is the right choice for:
- Medical equipment enclosures — clean, reflective appearance signals hygiene
- Display cases and retail fixtures — premium look for visible installations
- Cleanroom hardware — smoother surface reduces particle adhesion
- Decorative or architectural applications — aesthetics drive the specification
- Marine hardware — marginally better corrosion performance in salt environments
Selection Guide: Which Finish for Your Project?
| Factor | Vibratory Finish (ZG) | Mirror Polish (LG) |
|---|---|---|
| Appearance | Satin, matte silver | High-gloss, reflective |
| Fingerprint visibility | Low — barely visible | High — every touch shows |
| Scratch visibility | Low — blends with grain | High — every mark shows |
| Corrosion resistance | Same base SUS304 | Same base SUS304 |
| Cost premium | Baseline | 20–40% higher |
| Production speed | Fast (automated batch) | Slow (manual multi-step) |
| Batch consistency | High — process-controlled | Moderate — operator-dependent |
| Deburring included | Yes | No (separate step) |
| Best environment | Industrial, field, military | Medical, cleanroom, display |
Bottom line: choose vibratory finish when durability and low maintenance matter more than appearance. Choose mirror polish when the visual impression is the priority and the environment is controlled.
For reference, chrome plating on iron hardware (such as the 7201-50-FE-CR corner protector) sits between the two — glossier than vibratory finish but less reflective than a true mirror polish, with different corrosion characteristics due to the plated coating over carbon steel.
Frequently Asked Questions
What does ZG mean in NRH part numbers?
ZG stands for vibratory finish. It indicates the part has been processed through vibratory finishing media to produce a uniform satin texture. The 5101-96-S04-ZG butterfly latch, for example, uses this code per manufacturer catalog data.
What does LG mean in NRH part numbers?
LG stands for mirror polish. It indicates the part has been polished to a reflective, mirror-like finish. The 4201-110-0-S04-LG recessed handle is an example of this designation.
Is mirror polish more corrosion-resistant than vibratory finish?
Both finishes use the same SUS304 base material with identical chromium content. Mirror polish produces a marginally smoother surface with fewer micro-crevices, but the practical difference in salt-spray performance is negligible. Base material and environment matter more than surface polish.
Can I specify vibratory finish on a part that normally comes in mirror polish?
Many hardware items are available in both ZG and LG variants. Check the full SKU range for the product series. NRH Box Hardware offers multiple finish options across its SUS304 stainless steel catalog. Contact the factory for custom finish requirements.
Does vibratory finishing weaken the part?
No. Vibratory finishing removes only surface-level material — typically less than 0.01 mm. It does not affect tensile load, shear strength, or dimensional tolerance in any meaningful way. The process also deburrs and edge-breaks parts, which can improve fatigue life by removing stress concentrations.
Why does mirror polish cost more?
Mirror polishing requires multiple manual abrasive steps — coarse grind, fine grind, buff, and final polish. Each part is handled individually. Labor time per unit is significantly higher than the automated vibratory finishing process. Consumable costs for polishing compounds and cotton wheels also add up.
Which finish is better for outdoor equipment cases?
Vibratory finish. Outdoor cases get handled frequently, exposed to dirt and moisture, and transported in rough conditions. The satin texture hides wear, resists visible scratching, and does not show fingerprints. Mirror polish would require constant cleaning and show every mark.
Can a mirror-polished part be refinished to satin?
Yes. A mirror-polished part can be run through a vibratory finishing cycle to convert it to a satin texture. The reverse is also possible but requires re-polishing from scratch. If you anticipate needing to change finishes, starting with vibratory finish and upgrading to mirror later is more cost-effective than the reverse.
Need help choosing? Reach out to the NRH team at nrh-gz@nrh.cn or message us on WhatsApp at +86 180 1797 5137. We can help you compare finishes across our full catalog and recommend the right surface treatment for your application.
NRH Box Hardware — Room 1703-1704, Zhongji Building, No. 819 Yinxiang Road, Nanxiang Town, Jiading District, Shanghai, China