SSPC Publishes New Guide for Retrieval and Analysis of Soluble Salts

Pittsburgh--SSPC: The Society for Protective Coatings has published a new committee approved technology guide: SSPC-Guide 15, Field Methods for Retrieval and Analysis of Soluble Salts on Steel and Other Nonporous Substrates. The new SSPC-Guide 15 classifies and discusses the most commonly used field methods for the retrieval and analysis of soluble salts, the materials and procedures used during retrieval, analytical methods used to determine the concentration of the soluble salts in the extracted solution, and the relative advantages and limitations of each.

According to SSPC-Guide 15, retrieval methods employed to help determine surface concentrations of salt fall into three general classes:

• Class A involves a methodology for containing a liquid that is held in contact with a surface of a predetermined area. Turbulence within the contacting liquid enhances the dissolution of the salt contamination into the solution. Class A retrieval methods include the Patch Cell Retrieval Method and the Sleeve Retrieval Method.
  
  
• Class B involves a methodology for containing a known volume of liquid within a measured area that is in contact with the surface. There may or may not be mechanical rubbing of the surface. Class B retrieval methods include Swabbing or Washing Methods and the Filter Paper Extraction Method.
  
  
• Class C is used in a laboratory setting and involves immersing the entire surface in boiling water. This method uses a predetermined volume of extraction liquid and a predetermined surface area.

Class A and Class B methods can be used to help characterize surfaces encountered in either laboratory or field settings. In general, boiling extraction (Class C) methods are only useful under laboratory conditions. All the retrieval procedures described in this document use deionized or distilled water (designated as reagent water) or a proprietary solution.

SSPC-Guide 15 also examines analytical methods for determining salt concentration in the extracted solution, including:

• equipment and protocols for measuring conductivity
  (a measure of the total dissolved salts),
• field procedures for analyzing filter paper for soluble salts,
• procedures for field detection of the chloride ion by paper strip method and ion detection tube,
• field and laboratory titration methods for detection
  of the chloride ion,
• qualitative and quantitative field methods for detection
  of the ferrous ion, and
• field detection of sulfate and nitrate ions.

The ability to remove all of the soluble salt ions from the surface of a structure that has been in service for extended periods of time and is severely corroded and or pitted has not yet been demonstrated. It is important to note that all extraction tests remove less than 100% of the soluble salt ions from the structures, and the amount in the samples represents an unknown percentage of the amount actually existing on the structure. Therefore, the test methods indicated in this document are semi quantitative and do not represent the actual amount of soluble salt ions existing on the structure.

The appendices in SSPC-Guide 15 include:

• procedures and materials required for the boiling
  extraction method,
• conversion formulas for determining surface concentration
  from solution concentration,
• procedures for determining equivalent surface concentration
  from conductivity,
• factors affecting extraction efficiency,
• and sources of testing equipment and supplies.

Much of the information contained in the new SSPC-Guide 15 was originally found in the technology update SSPC-TU 4, Field Methods for the Retrieval and Analysis of Soluble Salts on Substrates. However, there have been several significant changes. For example, the new SSPC-Guide 15 contains a list of referenced standards, descriptions of the sleeve retrieval and filter paper extraction methods, and other details not found in the previous SSPC-TU 4. Other changes include the removal of certain retrieval and detection methods that are no longer widely used, and the addition of certain explanatory notes.

SSPC technology guides are documents that describe, review, or analyze new or improved technologies related to the use of protective coatings. They differ from standards in that they are not intended to be referenced in a specification or procurement document. Although not considered formal standards, these guides are nevertheless prepared by committee, undergo a review process, and are meant to represent a consensus of balanced interests. SSPC-Guide 15, Field Methods for Retrieval and Analysis of Soluble Salts on Steel and Other Nonporous Substrates, is the most recent of these documents.

The new SSPC-Guide 15 is one of the complete collection of SSPC standards, guides, and specifications that members can access through the new SSPC Members Only Download Area. Nonmembers can purchase PDF copies through SSPC Online Standards Store. It can also be found in the latest edition of Systems and Specifications, SSPC Painting Manual, Volume 2, available through the SSPC Online Bookstore.

For more information, please contact the SSPC Publication Sales Office by phone at 1-877-281-7772 (toll-free within the USA), or 1-412-281-2331 (if calling from outside the USA); by fax at 1-412-281-9992; or by email at books@sspc.org.