Technical Guide — Surface Treatment
Every supplier can give you a black watch case. Very few can give you a black watch case that passes ISO 10993 skin-contact testing, feels premium, and survives daily wear.
We learned the difference the hard way — six coating iterations on a real senior-wearable housing before we found the answer. Here's the honest comparison, so you don't repeat our trial and error.
The Five Coatings We Compared
Anodizing + Parylene C
● Good: deep black, biocompatible
● Bad: poor adhesion on this geometry, delamination, blurred masking edges
● Verdict: rejected
DLC (Diamond-Like Carbon)
● Good: ISO-compatible, extremely scratch-resistant
● Bad: color skews gray; bead blasting before coating clogged the threaded holes
● Verdict: partial — great for wear resistance, wrong for deep black
PVD
● Good: ISO-compatible, hard, durable
● Bad: grayish-black rather than deep black, not the premium look, higher cost
● Verdict: rejected for this application
Ceramic black (alone)
● Good: visibly black, cost-effective
● Bad: rough surface texture, tool marks stayed visible
● Verdict: partial
E-plating + ceramic black (the answer)
● Deep, pure black
● Smooth, premium hand-feel
● Fingerprint-resistant
● Passed all three ISO 10993 tests
● Verdict: selected
How to Choose for Your Own Part
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If you need... |
Look at... |
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Maximum scratch resistance |
DLC |
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Deep black + premium feel + skin safety |
E-plating + ceramic black |
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Lowest cost, less critical finish |
Anodizing or ceramic black alone |
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Hard wear + color flexibility |
PVD |
There is no single "best" coating — only the best coating for your color, feel, durability and compliance requirements. The mistake is letting a supplier pick for you based on what's easiest for them.
Two questions to ask any coating supplier:
1. "Can you show an ISO 10993 report for this exact coating?" (Not "it's biocompatible" — the actual report.)
2. "How do you protect threaded holes and adhesive zones during coating?" (If they hesitate, expect clogged threads and bonding failures.)
Not sure which coating fits your housing? Tell us your color, feel and compliance targets. We'll recommend a coating based on what we've actually tested — not what's easiest to apply. Free consultation, honest answer.
Shenzhen Tingfeng Hardware Products Co., Ltd. | tingfengprecision.com | Alibaba: sztfeng288