Stainless steel loggers and salt water

Following is an important application note regarding the deployment of the following products:

U20-001-01 – HOBO Water Level Logger
U12-015 – HOBO U12 Stainless Steel Temp Logger
U12-015-02 – HOBO U12 Stainless Steel Temp Logger with 5” probe

These products are made with 316 Stainless Steel and are resistant to corrosion in most circumstances. However, 316 Stainless Steel is susceptible to crevice corrosion when deployed in salt water, buried in mud or other substances, or when in contact with dissimilar metals. In these environments 316 Stainless Steel will eventually corrode, allowing water to enter and damage the electronics. The speed at which crevice corrosion occurs is dependent upon temperature and flow. In warm stagnant salt water or mud environments, the corrosion can start within hours and cause a leak in a month or less. In colder, faster-flowing environments, a leak may occur within six months. We recommend that you do not deploy stainless steel loggers in these types of environments.

The Titanium version of the U20 logger is ideal for use in salt water. Spending the extra $240 for Titanium U20 loggers will be justified the first time you do not destroy a $500 stainless logger by saltwater crevice corrosion.

HOBO® Water Level 30-Foot Titanium Data Logger U20-001-01-Ti

HOBO® Water Level 13-Foot Titanium Data Logger U20-001-04-Ti

Bag method for using stainless steel logger in saltwater: 

Place the stainless steel logger in a sturdy protective pouch filled with fresh water (or compatible fluid like propylene glycol). The pressure and temperature inside the protective bag will equalize with the surrounding water. Be sure that there is no air in the bag by submerging both the bag and logger in a bucket of fresh water as you seal the bag.

This method is risky for two reasons: 

  1. If the bag ever leaks, salt water will destroy your stainless steel logger
  2. If the bag tears, the logger will fall out and become lost

http://www.onsetcomp.com/waterLevel_logger_salt_water

An example of the type of pouch that we are referring to can be viewed and purchased at: http://www.aquapac.net (click on Mobile Phones & GPS cases, for example Small Whanganui case). 

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