In aerospace manufacturing, cleaning is a controlled process rather than a cosmetic step. Oil, particles, fingerprints and chemical residues can affect inspection, coating, bonding, assembly and component performance. A part may look clean while still carrying contamination that creates problems later in production.
Achieving AS9100 compliance requires organisations to control their processes and retain documented evidence where necessary. For cleaning operations, this means defining the process parameters, recording the results and showing that the method produces consistent outcomes.
Effective documentation should be clear enough for operators to follow and detailed enough to support an audit. Using an AS9100 compliance checklist can help manufacturers identify the key information to record and ensure important process controls are not overlooked. The following framework covers the main areas to include.
Define The Scope Of The Cleaning Process
Start by identifying exactly where the cleaning process applies. A general instruction such as "clean the component" does not give operators enough information or provide sufficient control.
The procedure should identify:
- Component or part family
- Material and surface condition
- Contamination being removed
- Previous manufacturing operation
- Cleaning equipment used
- Next process stage
- Applicable customer, OEM or internal specification
This context matters because cleaning requirements vary between applications. A process used before visual inspection may not be suitable before bonding, coating or non-destructive testing.
Clear scope also prevents an approved process from being used on materials or components that have not been assessed, helping manufacturers maintain consistent cleaning standards and meet applicable aerospace compliance requirements.
Identify The Cleaning Chemistry
Record the cleaning agent used for each application. A product name alone may not provide sufficient traceability, particularly if suppliers, formulations or approvals change.
Documentation should include:
- Product and chemical name
- Manufacturer and product reference
- Current technical and safety data sheets
- Batch or lot number where required
- Shelf life and expiry date
- Storage conditions
- Material compatibility
- Relevant OEM or customer approvals
Compatibility should be confirmed for the materials present, including aluminium, titanium, nickel alloys, steel, coatings and elastomers. Do not assume that a cleaner suitable for one metal is automatically suitable for another.
Any reference to Rolls-Royce, Airbus, Boeing or other OEM approval should be supported by current supplier documentation. Approval status, specification revisions and application restrictions should be checked as part of the document review process.
Control Dilution And Concentration
Cleaning performance depends on using the chemistry at the correct concentration. A weak solution may leave contamination behind. An unnecessarily strong solution can increase residue, waste chemistry or affect sensitive surfaces.
The procedure should define:
- Target concentration
- Permitted operating range
- Required water quality
- Mixing sequence
- Measuring equipment
- Verification method
- Test frequency
- Corrective action for an out-of-limit result
Concentration may be checked by titration, refractometry, conductivity or another approved method. The selected method should be appropriate for the chemistry and supported by clear instructions.
Operators should record the measured result rather than simply ticking a box to confirm that the bath was checked. This provides evidence that the solution remained within its approved operating range.
Specify Temperature And Cycle Time
Temperature and exposure time directly affect cleaning performance. These parameters should be defined as measurable limits rather than left to operator judgement.
Document the required:
- Minimum and maximum bath temperature
- Immersion or spray time
- Ultrasonic frequency and power, where applicable
- Agitation requirements
- Rinse time
- Drying temperature and duration
- Maximum delay before the next process
Monitoring equipment should be identified and included within the organisation's calibration system where appropriate. Records should capture the actual temperature and cycle time used.
If a process operates outside its specified limits, the procedure should explain how to isolate the affected components, assess the deviation and determine whether reprocessing is permitted.
Define Rinse Quality Requirements
Rinsing removes displaced contamination and residual cleaning chemistry. Poor rinse control can compromise an otherwise stable cleaning process.
The documentation should specify:
- Number and sequence of rinse stages
- Water quality required
- Rinse temperature
- Flow, agitation or overflow conditions
- Conductivity or pH limits
- Frequency of quality checks
- Criteria for replacing rinse water
Where deionised water is required, conductivity limits should be stated and measured using suitable equipment. Results should be recorded at a defined frequency.
The process should also prevent cross-contamination. This may require separate rinse tanks, controlled component flow or scheduled water replacement based on measured condition rather than appearance alone.
Establish Acceptance Criteria
"Visually clean" is too subjective unless the inspection conditions and acceptance criteria are defined. Operators and inspectors need a consistent method for determining whether a component has passed.
Depending on the application, checks may include:
- Visual inspection under specified lighting
- Water-break testing
- Ultraviolet inspection
- Surface residue testing
- Particle or gravimetric analysis
- Contact-angle measurement
- Customer-specific cleanliness testing
Document the test method, sample frequency, acceptance limits and response to failure. The selected criteria should reflect the risks associated with the component and its next manufacturing stage.
Validate And Monitor The Process
Initial validation demonstrates that the cleaning method can produce an acceptable result. Ongoing monitoring confirms that it continues to operate effectively.
Validation should consider the chemistry, concentration, temperature, cycle time, equipment loading, rinse quality and drying conditions. Where relevant, test worst-case conditions within the approved operating range.
Ongoing controls may include:
- Routine bath analysis
- Scheduled cleanliness testing
- Equipment maintenance
- Review of rejected components
- Internal process audits
- Periodic revalidation
- Trend analysis of recorded results
Changes to chemistry, equipment, materials or operating parameters should be reviewed before implementation. Revalidation may be required when a change could affect cleaning performance or the ability to meet aerospace compliance requirements.
Maintain Traceable, Audit-Ready Records
Auditors will compare the written procedure with actual shop-floor practice. Records should demonstrate that the approved process was followed for each relevant component, batch or production order.
A cleaning record may include:
- Component or batch identification
- Date and time
- Operator identification
- Equipment used
- Cleaning product and batch
- Concentration result
- Temperature and cycle time
- Rinse quality result
- Inspection outcome
- Deviations and corrective actions
Document control is equally important for maintaining AS9100 compliance. Procedures should carry a revision number, approval status and review date. Obsolete versions must be removed from points of use.
Training records should confirm that operators understand the process, its limits and the action required when a result falls outside specification.
Build A Process That Is Easy To Follow
AS9100 documentation does not need to be unnecessarily complex. A clear process sheet, supported by controlled work instructions, an AS9100 compliance checklist and concise records is often more effective than a lengthy procedure that operators find difficult to use.
Focus on the parameters that influence the result. Define measurable limits, record actual values and maintain traceability from the cleaned component back to the chemistry and process conditions used.
A well-documented cleaning process supports more than audit compliance. It improves consistency, reduces rework and provides evidence that contamination risks are being controlled.
Speak to our technical team to review your cleaning process and develop a clear, audit-ready framework for your application.
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