【Keywords】: inadequate cleaning by aqueous cleaning agent, workpiece rusting caused by cleaning agent, excessive foam of cleaning agent, deterioration of cleaning solution

【Abstract】: Inadequate workpiece cleaning, rusting, excessive foam and cleaning‑solution deterioration are four typical on‑site problems for aqueous cleaning. In most cases, these issues are not caused by failed cleaning agents themselves, but by improperly controlled process parameters such as concentration, temperature and solution maintenance.

I. Inadequate Workpiece Cleaning: Troubleshooting Checklist

Cleaning performance is sensitive to process conditions. Poor cleaning results are generally attributed to the following three factors:

Insufficient working concentration: Insufficient active ingredients reduce detergency. Solution: Raise the working concentration to the recommended range (normally 2%‑5%, subject to specific product grades).

Low cleaning temperature: Surfactants remain inactive if the operating temperature specified by the product is not reached. Solution: Heat the solution as required. For instance, CP‑600YM is recommended at 45 °C; CP‑25LG delivers significantly improved degreasing performance when heated to 60 °C.

Mismatched cleaning agent grade: The selected product is incompatible with contaminant types or workpiece materials. Solution: Switch to the proper grade according to workpiece material and contaminants. For example, use CP‑25LG for aluminum parts, CP‑600YM for cast iron, and CP‑26ZH for adhesive removal.

II. Workpiece Rusting

Rust protection failure due to low concentration: Excess water dilution lowers cleaning‑agent concentration and depletes anti‑rust components. Solution: Increase the working concentration.

Excessive dwell time inside equipment: Workpieces lose temporary surface protection during inter‑process stagnation. Workpieces shall be drained and transferred in a timely manner.

Confusing rust prevention with rust removal: Aqueous cleaning agents only provide short‑term rust prevention and possess no rust‑removal capability. Confirm workpieces are rust‑free before cleaning. Pre‑rusted workpieces shall be derusted prior to cleaning.

III. Excessive Foam During Cleaning

Excessive foam may overflow equipment and impair spray pressure as well as cleaning efficiency. Troubleshoot in the following sequence:

Check temperature: Foam volume decreases with rising temperature. Verify whether equipment temperature meets specifications.

Check concentration: Both over‑concentration and under‑concentration may trigger foaming. Adjust to normal working concentration. If foaming persists, add defoamer moderately; the regular dosage shall not exceed 0.5% of the stock cleaning‑agent volume.

Check impurity contamination: Long‑term service or carry‑over of upstream machining fluid into the tank easily causes foaming. Replace the cleaning solution, or add defoamer at 1%‑2% relative to stock agent volume. Defoaming treatment for upstream processes is also advised.

Check water level in tank: Over‑high water level tends to cause foam overflow.

Check for solution deterioration: Deteriorated working solution also generates foam. Replace the solution if peculiar odor occurs.

Equipment restart after long idle period: Foam will gradually subside after circulation, which is a normal phenomenon.

IV. Deteriorated Cleaning Solution (Foul Odor, Viscous Deposits)

Foul odor or viscous substance floating on the tank surface indicates solution degradation and massive bacterial growth. Countermeasures are listed below:

Emergency treatment: For heat‑capable equipment, heat the working solution to 70‑80 °C and circulate for 30 minutes, then add biocide.

Fundamental solution: Heating circulation can only relieve rather than eliminate deterioration. Complete solution replacement is required for thorough remediation.

Notes on solution replacement: Partial residual deteriorated solution will accelerate fresh‑solution degradation if full draining cannot be achieved. Residues from deteriorated solution must be sterilized during liquid change.

Source control: Bacteria from deteriorated upstream machining fluid will contaminate cleaning solution. Corresponding treatment for upstream processes shall be implemented.

V. Discoloration of Non‑Ferrous Metal Workpieces

Incompatible product grade: The cleaning agent is unsuitable for non‑ferrous metals. Switch to material‑specific grades (e.g. CP‑25LG for aluminum parts, formulated for non‑corrosive and discoloration‑free performance on aluminum).

Abnormal cleaning temperature: Operating temperature exceeds upper limit. Test actual tank temperature.

Malfunction of blow‑off unit: Check whether heating blow‑off temperature is over‑limit.

Upstream contamination: Check whether abnormal conditions already exist on workpieces before entering the cleaning station (such as residual chemicals from prior processes).

FAQ

Q: Will aqueous cleaning agents corrode workpieces?

A: No, when applied at recommended concentration, temperature and with properly matched grades. Corrosion or discoloration only occurs due to wrong grade selection (e.g. strong‑alkaline cleaner for aluminum parts) or over‑limit temperature. Dapeng Industrial has developed dedicated grades for aluminum, magnesium, copper and other materials.

Q: What is the proper dosage of defoamer?

A: For ordinary foaming issues, defoamer dosage shall not exceed 0.5% of stock cleaning‑agent volume. For severe foaming caused by impurity carry‑over, add defoamer at 1%‑2% relative to stock agent volume. Priority should be given to solution replacement and upstream‑process improvement.

Q: Does foul‑smelling cleaning solution mean deterioration? How to handle it?

A: Yes. Foul odor or viscous deposits indicate heavy bacterial proliferation. For emergency response, heat the solution to 70‑80 °C and circulate for 30 °C minutes with biocide added. Complete solution replacement is mandatory for fundamental resolution; sterilize and clean tank residues before filling fresh solution.