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VCS 1027 149

An independently developed accelerated laboratory corrosion test to evaluate corrosion resistance

Introduction

The Volvo VCS 1027, 149 test (also known as ACT-1) is a procedure developed to evaluate the corrosion resistance of metals, especially in sodium chloride rich environments from a marine influence or from winter de-icing solutions.

The test is intended to replicate the corrosion resistance to atmospheric conditions, in an accelerated but controlled way.

Test Conditions

The test method is composed of approximately 1% (+/- 0.1%) NaCL salt mist applications combined with a drying and controlled temperature and humidity phases, the length of the test process should be determined as part of the test procedure, however a 6 week test process should be sufficient to analyse bare metal or samples only protected by a thin coating, higher quality coatings may require as much as 12 weeks.

The recommended specification for the equipment required to undertake this test includes the use of oscillating spray nozzles located high up in the test chamber. These spray salt water solution down on to test samples located beneath, in a precise spray pattern, to ensure a uniform distribution of salt mist falling on the test objects with a flow corresponding to a downfall of 15 mm/h ±5 mm/h.

Forced drying is additionally recommended as part of the process, this is preferably achieved by creating a forced flow of pre-heated ambient air to ventilate the chamber. For a climate chamber of the volume between 1 and 2 m3, an airflow rate of 50 - 100 l/s is recommended. 

Method

Specimens being tested are exposed to a series of stages, exposing the samples to a variety of environmental conditions. The one-week main test cycle comprises of two twelve-hour sub-cycles, one with controlled cycling humidity, the other including the application of salt spray, these cycles detailed below;

First Sub Cycle

  • Constant temperature of 35 °C and relative humidity of 95% RH for a period of 4 hours.
  • An increase in temperature to 45 °C with a simultaneous linear decrease in relative humidity to 50% RH over the following 2 hours.
  • Maintained conditions of 45 °C and 50% RH for a further 4 hours.
  • A decrease in temperature to 35 °C with a simultaneous increase in relative humidity to 95% RH over a 2 hour period.

Second Sub Cycle

  • Salt spray application for 15 minutes.
  • Constant temperature of 35 °C for 1 hour 45 minutes with relative humidity of 95% - 99% RH to maintain wetness of the samples.
  • The above two steps repeated twice over a period of 6 hours.
  • Drying of the test objects, at relative humidity of 50% RH whilst increasing the temperature to 45 °C over the next 2 hours.
  • Maintained constant temperature of 45 °C and humidity of 50% RH for 2 hours.
  • Temperature decrease to 35 °C with a simultaneous increase of relative humidity to 95% RH over the final 2 hours.

Typical Application

Developed by Volvo, VCS 1027, 149 is a sophisticated corrosion test process that is widely utilised within the supply chain for supply of components to the Volvo Group. Note; this test has for some applications been superseded by VCS 1027, 1449 (also known as ACT-2).

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