Corrosion testing is fundamental to understanding how materials and coatings are able to resist aggressive environments. Some laboratories and manufacturers use the ASTM B117 salt spray test to determine product durability. Even experienced technicians make errors that compromise test accuracy and reliability.
Knowing such common pitfalls ensures consistent, meaningful results that are reflective of product performance.
A good initial setup is fundamental for reliable corrosion testing. Most problems appearing during or after testing result from mistakes made before the test begins. Environmental parameters and solution quality affect how corrosion forms on test specimens. Getting these basics right saves time and resources spent on invalid test runs.
A frequent error is improper temperature management in the salt spray test chamber. The standard requires an exposure zone of 35 °C (+/-1.7 0C). Some operators install temperature sensors too near heating elements or in areas where air circulation is poor. This creates hot spots where test conditions are not present.
The solution? Place several sensors throughout the chamber. Check calibration at least every three months. Temperature readings are documented at different locations to ensure uniformity over the test space.
Many people underestimate how critical proper solution preparation is. The NSS salt spray chamber requires 5% NaCl by weight. But using table salt instead of reagent-grade NaCl may introduce impurities, along tap water brings unwanted minerals and chlorine into the mix.
As a precautionary measure, always use deionized water for measurement salt concentration precisely with a hydrometer or refractometer. Fresh solution gives different results from a week-old mixture. Hence preparing batches regularly is the ideal approach.
How specimens sit inside the chamber matters more than most people realize. Poor placement creates inconsistent exposure conditions that make comparing results nearly impossible. The geometry and positioning of test pieces affect how salt fog contacts surfaces and how condensation drips. These seemingly minor details can invalidate an entire test cycle if overlooked.
Cramming too many samples into a corrosion testing chamber seems efficient but creates significant issues. Specimens block salt fog from reaching other samples. Dripping from upper samples contaminates those below, giving false results.
The standard specifies clear spacing requirements. Angle specimens between 15-30 degrees from vertical. Ensure fog can circulate freely around each piece. Yes, this means running more test cycles, but the data quality makes it worthwhile.
Rushing through cleaning steps before testing leads to unreliable outcomes. Oils from handling, dust particles, or residual manufacturing compounds create barriers that affect corrosion patterns. Some operators touch specimens with bare hands right before testing—a major no-no. Allow specimens to dry completely before placement in the salt fog test chamber.
Once testing begins, maintaining correct operating conditions becomes crucial for valid results. The salt spray chamber test method specifies several parameters that work together to create standardized corrosion conditions. Deviations in any single parameter can alter the corrosion mechanism or rate significantly. Continuous monitoring throughout the test period prevents drift from specified conditions.
The salt spray chamber test method requires specific atomizer pressure—typically between 0.7 to 1.2 kg/cm². Running too high creates excessive spray that pools on specimens. Too low produces inadequate fog coverage.
Install quality pressure gauges. Verify the collection rate meets standards: 1.0 to 2.0 mL per hour per 80 cm² of horizontal collection area. Check this weekly, not just during initial setup. Nozzle wear changes spray patterns over time, affecting results even when pressure readings look normal.
Salt spray testing isn't just about the spray itself. The chamber must maintain 95% or higher relative humidity at test temperature. Dry conditions accelerate evaporation and alter the corrosion mechanism being studied.
Modern corrosion test equipment includes built-in humidity monitoring, but older units may not. Add quality humidity sensors if needed. Keep the chamber sealed properly; even small leaks affect internal conditions significantly.
Proper documentation separates professional testing labs from amateur operations. Complete records allow others to understand exactly what happened during testing and reproduce results if needed. Missing information raises questions about data validity and makes troubleshooting impossible when unexpected results occur. Comprehensive documentation also protects against disputes about test conditions or outcomes.
Surprisingly, inadequate documentation ranks among the most common errors. Operators record test duration but forget to note solution pH, chamber location of each specimen, or environmental conditions outside the unit. When questions arise about results, missing information makes troubleshooting impossible.
Create standardized data sheets that prompt recording all relevant parameters. Include photographs of specimen placement and initial appearance. Log maintenance activities, calibration dates, and any deviations from standard procedures.
Not all corrosion represents test failure. The evaluation criteria depend on product specifications and intended use. Some operators mark slight discoloration as "failed" when the standard allows for surface changes that don't compromise functionality.
Develop clear acceptance criteria before testing begins. Train evaluators using reference standards. Consider having multiple people assess results to reduce subjectivity.
Regular maintenance prevents many testing errors. Inaccurate cleaning of the salt spray chamber equipment causes salt buildup, which changes spray patterns and causes contamination. Atomizer nozzles need periodic replacement - they do not last.
Proper maintenance protects the machine. Moreover, most of the time, people often pay attention to the quality, as salt spray chamber price in India varies, but it will perform reliably for years.
Accurate ASTM B117 testing involves many details. Every step, from solution preparation to final evaluation, contains error opportunities. Knowing such common errors and taking preventive steps helps laboratories achieve consistent, defensible results. Quality corrosion testing programs base their programs on regular training/documentation/equipment maintenance.
If you too want to perform an accurate and reliable salt spray test, contact Presto Group.
Call us: +91 9210903903
Email: response@prestogroup.com
Address: Plot No. I, 42, NH-19, Block C, DLF Industrial Area, Sector 32, Faridabad, Haryana 121003
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