How to Perform Acid Acceptance Testing for nPB in Vapor Degreasers

Acid acceptance testing is a vital maintenance step for any facility using n-propyl bromide (nPB)-based solvents in a vapor degreaser. Without regular monitoring, these solvents can degrade into corrosive acids that damage equipment, create safety hazards, and result in high cleanup and disposal costs.

This guide outlines how to perform acid acceptance testing and interpret the results to maintain a stable, effective vapor degreasing process.

Why Acid Testing Matters
nPB-based solvents are prone to turning acidic under certain conditions, including:

Prolonged exposure to heat during the cleaning cycle
Residual acid in cutting oils or parts
Moisture contamination from prior processes (e.g., plating or rinsing)

When the solvent “goes acid,” it can corrode the vapor degreaser’s internal components, damage parts, and require costly remediation. Regular acid testing helps identify problems early—before permanent damage occurs.

Testing Frequency
Perform acid acceptance testing weekly. A simple 10-minute test is enough to determine if your solvent has become acidic or if stabilizers need to be replenished.

Materials Needed

Solvent sample from the vapor degreaser
Two test reagents: Solution A (indicator) and Solution B (neutralizer)
Pipette and test vial with marked measurements
Stopwatch or timer
Instructions or reference chart for interpretation

Step-by-Step Procedure

Step 1: Collect the Solvent Sample

Use a clean pipette to draw solvent from the degreaser.
Measure 1.5 ml using the pipette’s hash marks.
Dispense the sample into the test vial.

Step 2: Add Solution A (Indicator)

Add Solution A (yellow reagent) to the test vial until the liquid reaches the 3.5 ml mark.
Seal and shake the vial.
Let the mixture sit for exactly 10 minutes. Timing is critical for accurate results.

Step 3: Add Solution B (Neutralizer)

After 10 minutes, add Solution B drop by drop into the vial.
Shake after each drop and observe the color change.
Count the number of drops until the solution turns a complete blue.

How to Interpret Results

Fewer than 15 drops: Solvent is stable. No action needed.
15–40 drops: Add stabilizer. Refer to your chart to calculate how much based on drops and solvent volume.
More than 40 drops: Solvent is overly acidic. Consider replacing it completely.

Best Practices

Use only clean, dry tools to avoid skewing test results.
Document test results weekly for traceability and preventive maintenance tracking.
If water, plating fluids, or acidic oils are frequently introduced to the process, increase testing frequency.

Benefits of Regular Testing

Prevents equipment damage and downtime
Ensures part quality and consistency
Reduces solvent replacement costs
Maintains compliance with safety and quality standards

Summary
Acid acceptance testing is simple, fast, and cost-effective. Performing this test weekly allows you to keep your nPB-based cleaning system running safely and efficiently. A stable solvent environment protects your vapor degreaser, your parts, and your bottom line.

If you're unsure how to interpret your results or need help determining stabilizer dosing, contact the MicroCare Team of Experts for guidance.