At William Hughes, we specialise in precision passivation for stainless steel, using advanced chemical treatments and rigorous quality control to meet the highest industry standards, including AMS2700 and ASTM A967. Passivation is a chemical process used on corrosion resistant steels to remove free iron and surface contaminants without altering the material’s essential properties. This process restores the natural oxide layer, reducing the risk of corrosion and ensuring optimal functionality across a wide range of manufacturing applications.
Whether you require passivation for medical instruments, precision-engineered components, or complex assemblies, William Hughes delivers results that meet stringent industry specifications.
Our Passivation Process
Our passivation process, which is Nadcap accredited and Honeywell Aerospace approved, involves a series of precise chemical treatments that eliminate contaminants from the stainless steel surfaces. Our facility at Stalbridge incorporates an automated passivation plant offering a ‘fluid transfer’, which involves moving chemical solutions from holding tanks into the main processing unit as required, helping to prevent damage as the parts do not move. The entire process is automatic and PLC controlled. Typical treatments are nitric acid and rinse cycles. These are followed by a final rinse in deionised water before a drying cycle.
We offer three service levels: standard five-day, express three-day and super express 24 hours (subject to any testing requirements).
The working envelope size available is 520 x 300 x 200mm.
Our multi-stage passivation process includes:
The Process
- Pre-Cleaning: Components are meticulously cleaned using ultrasonic techniques to remove oils, machining residues, and particulates.
- Acid Immersion: Stainless steel parts are immersed in a carefully controlled acid bath to dissolve iron contaminants.
- Neutralisation and Rinse: Acid residues are neutralised, and components are rinsed thoroughly to remove residual chemicals.
- Drying and Inspection: The parts are air-dried in a clean room environment to prevent recontamination.
This systematic approach ensures that the stainless steel is not only corrosion-resistant but also maintains its mechanical properties and surface finish, crucial for high-stakes manufacturing applications.
This systematic approach ensures that the stainless steel is not only corrosion-resistant but also maintains its mechanical properties and surface finish, crucial for high-stakes manufacturing applications.
Types of Passivation Cleaning
Passivation at William Hughes utilises a range of cleaning techniques to prepare and treat stainless steel components effectively. Each method is chosen based on the specific contaminants present and the intended application of the component.
Approvals and Accreditations
- AASTM A967: Specification for Chemical Passivation Treatments for Stainless Steel
- ISO 9001: Quality Management Systems
- AMS2700 Method 1
Example Application: Ultrasonic Cleaning & Passivation of Stainless Steel Spring Assemblies
In many precision manufacturing applications, particularly when we make spring wire forms from stainless steel, post-machining and forming processes often leave behind localised surface oxidation, residual lubricants, and metallic contaminants. These residues can severely undermine long-term corrosion resistance, especially in environments with elevated humidity or exposure to reactive media such as fuels, salts, or hydraulic fluids.
To mitigate these risks, components are first subjected to ultrasonic cleaning, using high-frequency sound waves in specially formulated cleaning solutions. This non-destructive, deep-penetration method removes oils, metal fines, and oxides from even the most intricate geometries, including coiled or enclosed wire forms. The result is a chemically clean surface, ready for downstream treatments.
Following ultrasonic cleaning, stainless steel components may undergo passivation — a chemical process that removes free iron from the surface and enhances the formation of a protective chromium-rich oxide layer. This step significantly improves the material’s resistance to pitting, crevice corrosion, and surface degradation without altering the mechanical or dimensional properties of the component.
Our passivation processes are fully aligned with ASTM A967 and IATF 16949 standards and are routinely validated through destructive and non-destructive testing. Treated components typically exceed industry benchmarks for corrosion resistance, passing salt spray and humidity testing with wide safety margins. Crucially, no measurable changes in tensile strength or dimensional integrity are observed, ensuring that springs retain their designed performance characteristics, even in high-pressure or high-temperature systems.
This combined approach, ultrasonic cleaning followed by precision passivation, is especially critical in sectors such as automotive, aerospace, and medical manufacturing, where material integrity and surface condition directly influence system reliability. In practice, customers who adopt this dual-process strategy often see a marked reduction in corrosion-related field failures, backed by traceable quality assurance documentation that supports full regulatory and industry compliance.
Quality and Inspection Techniques
William Hughes implements a comprehensive quality assurance programme, integrating advanced inspection methods to validate the passivation process:
- Visual Inspection: To detect surface irregularities and residual contamination.
- Corrosion Resistance Testing: Following AMS2700 and ASTM A967 protocols to confirm the effectiveness of the passive layer.
With our commitment to precision and quality, every batch undergoes meticulous documentation and traceability procedures, ensuring compliance with regulatory and customer specifications.
FAQs
These are questions that we often encounter when discussing our Passivation services with a new customer.