How to assess if a surface treatment provider qualifies for aerospace or medical titanium?
A surface treatment provider qualifies for aerospace or medical titanium only when its quality system, process controls, traceability, validation evidence, and nonconformance handling match the exact drawing and regulatory risk of the part. A certificate alone is not enough. The buyer should verify which titanium treatment is being performed, which specification controls it, whether the provider is approved by the customer or prime contractor, and whether the finished surface can be traced from incoming material through cleaning, masking, treatment, inspection, packaging, and release.
1. Certifications and Quality Management Systems
Quality certifications are screening evidence, not automatic approval. The useful question is whether the certificate scope covers the site, process, material, and part family being quoted.
Aerospace: AS9100 with ISO 9001 is commonly expected for aerospace suppliers, but the customer flow-down still controls the final requirement. For special processes, Nadcap accreditation may be required for the exact process family, such as chemical processing, anodizing, passivation-style cleaning, heat treatment, or coating. Nadcap is valuable because it reviews process control details, but the accreditation scope, expiration date, and commodity checklist must match the job.
Medical: ISO 13485 is relevant when the supplier operates inside a medical device quality system or performs controlled outsourced processes for medical devices. FDA 21 CFR Part 820 applies to U.S. medical device quality system controls and supplier control expectations, but it does not automatically make every finishing shop a device manufacturer. For implant-grade titanium, material and finished-surface requirements may reference ASTM F136 for Ti-6Al-4V ELI, ASTM F86 surface preparation or marking practices, customer specifications, and biocompatibility validation plans.
2. Material and Process Traceability
Traceability must connect the titanium material, machined part, surface treatment lot, process parameters, inspection records, and final release documents without relying on memory or manual reconstruction after a problem appears.
Lot Control: The provider must segregate and track parts by lot through receiving, cleaning, masking, CNC machining interface steps, surface treatment, inspection, rework, and packaging. Mixed titanium, aluminum, and stainless workflows need physical or procedural separation to prevent contamination.
Material Certification: Certified material test reports should trace back to the mill and match the purchase order, heat number, alloy grade, condition, and customer specification. For medical or aerospace titanium, the reviewer should confirm that the material certificate and treatment traveler use the same lot identity.
Process Travelers: A traveler or job card should record cleaning sequence, bath identity, chemical concentration, temperature, voltage or current density, treatment time, masking method, rack contact, rinse steps, inspection result, operator, equipment, and release authority. Missing traveler fields are a supplier qualification warning sign.
3. Process Control and Documentation
The qualification review should verify whether the supplier can repeat the actual surface treatment, not whether it can describe the process in a brochure.
Approved Process Specifications: The supplier should work to customer-approved procedures, drawing notes, or relevant industry specifications such as AMS 2488 for titanium anodic treatment when specified, ASTM F86 for selected medical titanium surface preparation and marking practices, or Nadcap chemical processing requirements when flowed down. Generic statements like aerospace coating available are not enough.
Controlled Procedures: Detailed work instructions should define parameters such as solution chemistry, bath age, temperature, voltage, current density, time, agitation, rinse quality, drying method, masking, rack contact, and allowed rework. Revision control matters because a small change in cleaning, voltage, or dwell time can change color, oxide thickness, hydrogen risk, or fatigue behavior.
Pre-Treatment Cleaning & Etching: Cleaning is a high-risk step for titanium. The provider should control alkaline cleaning, acid pickling, etching, deionized water quality, drying, and contamination prevention. Poor cleaning can cause coating loss, discoloration, hydrogen uptake, pitting, or biological cleanliness failure.
4. Testing and Validation Capabilities
Qualification should include the tests needed by the drawing and application, plus evidence that test equipment, sampling frequency, and acceptance criteria are controlled.
Coating Quality Tests: Ability to perform and document:
Coating Thickness: X-ray fluorescence (XRF), eddy current, cross-section microscopy, or another suitable method depending on coating type, thickness, substrate, and feature access.
Adhesion: Tape tests such as ASTM D3359, bend tests, scratch tests, or customer-defined adhesion checks when those methods fit the coating and part geometry.
Corrosion Resistance: ASTM B117 salt spray, cyclic corrosion, immersion, or application-specific seawater exposure testing when the part actually needs corrosion validation.
Surface Resistivity: Electrical resistance or dielectric testing when anodized or MAO titanium must provide insulation or controlled conductivity.
Material Integrity Tests (Critical for Medical):
Biocompatibility Certification: The supplier should provide process records, cleanliness evidence, and material compatibility data needed for biological evaluation under ISO 10993. The finishing shop should not claim that a surface treatment alone certifies the final medical device.
Fatigue Testing: Fatigue-sensitive parts need evidence that blasting, anodizing, MAO, PVD, polishing, or peening does not damage the required fatigue performance. The evidence may be a validated process window, representative coupons, residual stress checks, roughness limits, or customer-approved first article tests.
5. Supplier Qualification Checklist
During an on-site or virtual qualification review, directly assess the following and request objective records instead of verbal confirmation:
Facility Cleanliness: Confirm segregation between titanium, aluminum, stainless, blasting, polishing, cleaning, and coating areas. Cross-contamination can change corrosion behavior, color, adhesion, and biological cleanliness.
Chemical Management: Review tank analysis frequency, bath life limits, concentration records, pH or conductivity checks, DI water control, filtration, and preventive maintenance evidence.
Personnel Training: Check whether operators are trained and authorized for the exact work instruction, not only for general surface treatment work.
Non-Conformance System: Review how out-of-spec parts are quarantined, investigated, dispositioned, corrected, and prevented from recurrence through CAPA. A useful system links the defect to the affected lot, parameter record, root cause, and customer notification rule.
Final Inspection: Review final inspection reports for coating thickness, visual criteria, critical dimensions after treatment, cleanliness, packaging, certificate content, and any customer-specific release signature.
