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The Technology Behind Our Stainless Steel

Three things set our stainless steel apart: PVD color coating that is thicker and more consistent than typical market product, anti-fingerprint coatings that keep surfaces clean with one wipe, and production tested to recognized national and international standards. Each one is shown below with real measurements.
PVD coating  ·  Anti-fingerprint  ·  Recognized standards  ·  Every figure names its test method
PVD coating standard

Thicker coating, tighter color, tested on every order

We color stainless steel two ways: full coils for standard PVD colors, and sheet by sheet for special colors and small batches. The figures below are measured on our coil-coated production, against typical market product.
0.30µm
Typical coating thickness, 0.25 µm minimum
3,500+
MEK solvent rubs without wearing through
10/ 10
Neutral salt spray rating, GB/T 10125
±1
LAB color tolerance on a* and b*

Ahead of typical market product on every test

Same tests, side by side, on coil-coated PVD. The same standard applies to titanium gold, rose gold, black and every other coil color.
Salt spray is rated 0 to 10. A rating of 10 means no corrosion.
Property
Sanmei Metal PVD
Typical market
Coating thicknessCalotest (ball cratering)
≥ 0.25 µmtypically 0.30–0.32 µm
0.21–0.27 µm
MEK solvent rubWear and cleaning-agent resistance
> 3,500 rubs
> 3,000 rubs
Neutral salt sprayGB/T 10125 (≈ ISO 9227)
Rating 10
Rating 9
AdhesionGB/T 5270 cross-hatch
No flaking
Up to ~5% flaking
Color toleranceSpectrophotometer, CIE LAB
±1 a* / b*±2 L* on dark tones
Often unspecified

Up to 28% thicker coating, so the color lasts longer

Measured under the microscope with the ball-cratering method: a steel ball grinds through the coating, and thickness is calculated from the ring it leaves. 0.301 µm on our coil-coated titanium gold, 0.235 µm on a typical market coil.
Titanium Gold
+28% coating
ti gold coating of pvd sheets under microscope in market
Typical market
0.235 µm
ti gold coating of pvd sheets under microscope in sanmei metal
Sanmei Metal
0.301 µm
Rose Gold
+28% coating
ti gold coating of pvd sheets under microscope in market
Typical market
0.250 µm
ti gold coating of pvd sheets under microscope in sanmei metal
Sanmei Metal
0.319 µm

The same color across every coil and every sheet

Standard colors are coated as full coils and held to a tight tolerance. Special colors are coated sheet by sheet against a recorded reference. Both are measured with instruments, never judged by eye.
inline LAB mobitoring in sanmei metal
Step 1 · on the coating line
Inline monitoring
A LAB sensor reads the coil continuously while it is coated. If the color starts to drift, the line is corrected before the coil is finished.
LAB mobitoring in sanmei metal
Step 2 · after coating
Offline check
Finished coils are measured again with a handheld spectrophotometer to confirm the color matches its target.

How big a color difference (ΔE) can the eye see?

ΔE < 2
Most people see no difference
Where every PVD color we supply is held.
ΔE 2–5
Visible with two sheets side by side
Shows on a wall built from mixed batches.
ΔE > 5
Reads as a different color
A rejected batch on any project.

Coil-coated colors: target and allowed range

Color
Target value
Allowed range
Max. ΔE
To the eye
Titanium Gold
b* 32
±1
1.0
Not visible
Rose Gold
a* 12, b* 22
±1 each
1.4
Not visible
Black
L* 47 mirror / 40 hairline
±2
2.0
At the limit
Titanium Gold, anti-fingerprint
b* 33–34
±2
2.0
At the limit
Black, anti-fingerprint
L* 35
±2
2.0
At the limit
Max. ΔE is the worst case, with every value at the edge of its range at once. Rose gold: √(1² + 1²) = 1.4. Black only varies in L*, so its worst case is 2.0.
ΔE ≤ 2
Every coil-coated color is held at or below the point where a difference becomes visible, and far from ΔE 5, where a sheet reads as a different color.

Sheet-coated colors: reference values

For special colors and small batches, we coat individual sheets on mirror, hairline, cross hairline or sandblasted base. Each color has a recorded LAB reference, and coated sheets are measured against it. You can also send an approved sample as the target.
Purple Hairline Stainless Steel Sheet S26HL-17
Purple
Mirror
L* 50.73 · a* 11.38 · b* 0.06
rose gold stainless steel sheet
Rose Gold
Hairline
L* 55.21 · a* 12.10 · b* 11.27
Titanium Gold Hairline Finish Stainless Steel S26HL-06
Titanium Gold
Hairline
L* 71.90 · a* 3.86 · b* 35.49
PVD Black Titanium Hairline Stainless Steel Sheet S26HL-11
Black
Hairline
L* 35.76 · a* -0.10 · b* 0.50
New to color measurement?

What do L*, a* and b* mean?

Color is not judged by eye. A spectrophotometer reads every surface as three numbers in the international CIE LAB color system.
L* · Lightness. 0 is black, 100 is white. A lower number means a darker sheet.
a* · Green to red. Below 0 leans green, above 0 leans red. Rose gold has a high a*.
b* · Blue to yellow. Below 0 leans blue, above 0 leans yellow. Gold has a high b*.

How is ΔE calculated?

ΔE (delta E) turns the differences in L*, a* and b* into one number. Measure the target and the actual sheet, subtract each value, square the three differences, add them, and take the square root.
ΔE = √( ΔL*² + Δa*² + Δb*² )
Example, rose gold:
 
L*
a*
b*
Target
68.0
12.0
22.0
Sheet measured
68.0
12.8
21.4
Difference
0
0.8
−0.6
ΔE = √(0² + 0.8² + 0.6²) = √1.00 = 1.0, below 2, so no visible difference.

Can you match a color sample we already approved?

Yes. Send the approved sample. We read its LAB values and use them as the production target, with the same tolerance shown above.

Fingerprint-resistant surfaces that wipe clean

An anti-fingerprint (AF) coating is a clear top layer over the PVD color. Fingerprints barely show, and one wipe cleans the surface. Our standard AF withstands 215 solvent wipes; typical market AF wears through at 70.
Roll-coated, over 2 µm thick · tested to YB/T 4333

Standard AF

Test
Sanmei
Typical market
Coating thicknessA thicker film lasts longer
> 2 µm
< 2 µm
Butanone (MEK) rubSolvent wipes before the film wears through. Required: over 100
215
70
Pencil hardnessScratch resistance. 3H is harder than 2H
3H
2H
Cupping testHow deep the sheet can be pressed before the film cracks
> 8 mm, no crack
Cracks at 7 mm
90° T-bendSheet bent to 90°, checked for cracks
No crack
Slight cracking
Under 20 nm thick · no color shift

Nano AF

Water contact angle
> 115°
Water beads up and rolls off
Pencil hardness
> 6H
Very high scratch resistance
Salt spray, acid, alkali
> 48 h
No damage after 48 hours
Heat resistance
250 °C
Held for 100 hours
Artificial sweat
> 72 h
Resists skin oils and sweat
After steel wool rubbing
> 90°
Still repels water
Used on range hoods, dishwashers, cooktops, grease filters and product panels. Available on titanium gold, rose gold and black PVD finishes.

Made and tested to recognized standards

Base steel, coating and corrosion tests follow Chinese national standards. Where an international equivalent exists, it is shown next to the code, so your team can match it to the specs they already use.

Base steel

GB/T 3280
Cold-rolled stainless steel plate, sheet and strip
T/FSMA 002-2018
Cold-rolled austenitic stainless steel decorative sheet
GB/T 222
Permitted deviations in chemical composition of steel products

Coating performance

GB/T 7707
Ion-plated coating thickness, ball-cratering method
GB/T 5270≈ ISO 2819
Adhesion test methods for metallic coatings
GB/T 9754≈ ISO 2813
Specular gloss at 20°, 60° and 85°

Corrosion

GB/T 10125≈ ISO 9227
Salt spray testing in artificial atmospheres
GB/T 6461≈ ISO 10289
Rating of coated specimens after corrosion tests

Finishing & delivery

YB/T 4333
Anti-fingerprint stainless steel decorative sheet
GB/T 2480
Silicon carbide abrasives for surface finishing
GB/T 247
Packing, marking and quality certificates for steel sheet and strip
Tell Us About Your Project
Every order ships with a Mill Test Report. SGS test reports and LAB color readings are available on request.

Contact us

Creating Center, Shunde District, Foshan City, Guangdong Province, 528315, China
+8615015653566 / 0757-87668353
Paige Deng
marketing@sanmeimetal.com

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    TEL: +8615015653566 / 0757-87668353
    Email: marketing@sanmeimetal.com

    Headquarters:
    Creating Center, No.142, Yuhe Road, Lecong Town, Shunde District, Foshan City, Guangdong Province, China. 528315

    Factory: Liyuan Logistics City, Chencun Town, Shunde District, Foshan City, Guangdong Province, China. 528313

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