Compare SiC 88% Vs 90% Purity, Same 80 Grit – Which Is Better For Metal Polishing?
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Compare SiC 88% vs 90% Purity, Same 80 Grit – Which Is Better for Metal Polishing?
In metal polishing, achieving a smooth, scratch‑free finish depends not only on the abrasive grit size but also on its chemical purity. A frequent point of comparison is silicon carbide (SiC) at 88% purity versus 90% purity, both in the same 80 grit (≈180 µm particle size). While the grit is identical, the difference in impurity content changes how the abrasive interacts with the workpiece, influencing cutting consistency, surface cleanliness, and final finish quality.
At ZhenAn, with 30 years of experience supplying SiC abrasives for metal finishing, we break down which purity performs better for metal polishing and explain why.
1. Metal Polishing: Key Objectives
Metal polishing aims to:
Produce a uniform surface finish (mirror, satin, or matte as required)
Minimize visible scratches and micrometre‑scale defects
Avoid embedding of abrasive particles that can cause discoloration or corrosion
Maintain dimensional accuracy (controlled material removal)
The abrasive must cut predictably, fracture evenly, and not introduce hard, irregular contaminants.
2. Same 80 Grit - What Changes with Purity?
80 grit fixes the particle size distribution → same initial cutting depth and contact area.
88% SiC: ~12% impurities (mainly silica, free carbon, metal oxides).
90% SiC: ~10% impurities → more actual SiC per unit mass.
Impurities affect polishing because they:
Fracture Irregularly → create random deeper scratches.
Can Embed in softer metals, leaving permanent marks.
React Chemically → silica residues may affect surface appearance or coating adhesion.
Cause Non‑Uniform Wear → some grains degrade faster, reducing consistency.
3. Performance Comparison: 88% vs 90% Purity (80 Grit)
|
Factor |
SiC 88% Purity |
SiC 90% Purity |
|---|---|---|
|
Active SiC Content |
Lower → less efficient cutting per gram |
Higher → more efficient cutting per gram |
|
Impurity‑Induced Irregularity |
More frequent random scratches |
Fewer random scratches |
|
Embedded Particle Risk |
Higher |
Lower |
|
Surface Cleanliness |
May show silica residue |
Cleaner finish |
|
Cutting Consistency |
Variable over time |
More consistent |
|
Suitability for High‑Finish Metals |
Moderate |
Better (especially stainless, aluminum, copper) |
Result: With the same grit, 90% purity delivers a smoother, more consistent finish due to fewer impurities and more uniform cutting action.
4. Why 90% Purity Is Better for Metal Polishing
Higher SiC Content → more usable cutting edges per gram, so less abrasive is needed for the same result.
Fewer Rogue Particles → impurities are primary cause of random deep scratches in precision polishing.
Cleaner Action → less chemical reaction with metal surface or polishing lubricant, preserving brightness and color.
Longer Life in Process → consistent wear means fewer changes of abrasive belt/disc, improving productivity.
For metals where appearance and corrosion resistance matter (e.g., stainless steel, brass, nickel alloys), 90% purity reduces post‑polish defects and rework.
5. Practical Selection Guide
High‑Aesthetic or Food‑Grade Metals → choose 90% SiC for minimal contamination and highest finish quality.
General Industrial Polishing with cost constraints → 88% SiC may be acceptable if minor scratches are tolerable.
Progressive Polishing Sequences → use 90% SiC in final stages to lock in smoothness.
Lubrication & Pressure Control → even high purity needs proper technique to avoid heat discoloration or embedding.
6. Industry Example
A manufacturer of architectural stainless steel panels switched from 80 grit SiC 88% to 80 grit SiC 90% for final surface preparation:
Reduced visual defects by ~45%
Achieved more uniform satin finish across production batches
Lowered polishing time in final inspection and touch‑up
7. Why Choose ZhenAn for Metal Polishing SiC
30 years of experience producing tightly sized, high‑purity SiC for metal finishing
Consistent quality: ISO & SGS certified, precise control of purity (88%, 90%, higher) in same grit sizes
Custom abrasive papers, belts, or compounds for automated or manual polishing lines
Global supply ensuring reliable delivery to metal fabricators worldwide
Conclusion
For metal polishing with the same 80 grit, 90% SiC purity is better than 88% purity. The higher purity reduces impurity‑driven random scratches, lowers embedding risk, and ensures a cleaner, more consistent surface finish - critical for high‑value metal applications. Although 88% SiC may be cheaper per kilogram, 90% SiC often improves yield and reduces rework, offering better overall value in precision polishing.
For expert advice on SiC grit and purity selection for your metal polishing process, contact our finishing specialists at:
FAQ
Q1: Does a 2% purity difference really matter in polishing?
A: Yes - in precision metal polishing, even small impurity changes affect scratch consistency and surface cleanliness.
Q2: Can I mix 88% and 90% SiC to balance cost and quality?
A: Possible, but blending may reduce finish consistency; better to use 90% in final stages for critical surfaces.
Q3: Is 80 grit too coarse for mirror polishing?
A: Yes - 80 grit is typically a medium stage; mirror finishes require much finer grits (e.g., 240+ grit).
Q4: Does ZhenAn supply 80 grit in both 88% and 90% purity?
A: Yes, we offer both purity levels in 80 grit and can customize for your process.
Q5: Will higher purity SiC extend tool life in polishing?
A: Yes - more uniform wear means longer consistent performance before replacement.
