Copper Naphthenate (CuNap) was originally developed for wood (as a brush on preservative), textiles and other cellulosic materials in the early 1900s and was standardized by the AWPA in 1948. In the late 1980s, its use was expanded to utility wood treated poles and crossarms. More recently, CuNap has been standardized by the AWPA for the treatment of railway ties.

CuNap Performance Review

In 2016, Jim Brient published a review on CuNap that detailed several efficacy and performance studies. This paper noted:

  • a. Posts treated to only 23% of the AWPA minimum required CuNap preservative retention had an estimated service life of 65 years.
  • b. Wood test stakes treated with CuNap performed comparably to those treated with either creosote or pentachlorophenol at similar retentions.

The review also noted that CuNap performed comparably to both creosote and pentachlorophenol in terms of linemen gaff penetration. There have been no significant performance issues over the past 20 years with CuNap treated wood utility poles due to fungal decay or termite attack.

CuNap Environmental Registration

Copper naphthenate has a toxicity profile which allows it to be classified as a General Use Pesticide by the US EPA. With this classification, CuNap at lower concentrations than used for industrial treating, is available as an over-the-counter brush on preservative at hardware and paint stores for residential and commercial applications. The most recent EPA registration review on CuNap concluded that no additional data would be required and the current approved uses, including utility poles and crossarms, will continue.

CuNap General

CuNap treated wood is non-conductive and acts similarly to untreated wood in conductivity tests. In addition, CuNap treated wood has low corrosion properties. Currently, a limited number of utility pole treatment companies offer CuNap treated wood poles.