SANDPOINT — The Idaho Transportation Department is testing the efficacy of adding corrosion inhibitor to its deicer mix in Bonner County this winter.

The department wants to nail down whether the additive will curb the corrosive effect of salt brine that’s being used to keep state highways clear of snow and ice, according to Damon Allen, ITD’s District 1 engineer.

The product, ArcticClear CI Plus, is being added to the brine solution.

“Of all the corrosion inhibitors, it seems the most promising,” said Allen.

Metal “coupons” — sets of painted steel washers — are being installed on ITD rigs, which are washed daily, and on Northern Lights Inc. vehicles, which are not. The coupons will also be placed on roadsides.

Allen said a third-party consultant will weigh and measure the coupons to determine if the ArcticClear is effective in combating corrosion caused by the salt brine.

The results will be compared against coupons installed on vehicles in Benewah County, which will be using unadulterated salt brine this winter.

ArcticClear CI Plus is approved for use as a corrosion inhibitor for sodium chloride brine, according to Pacific Northwest Snowfighters, association of transportation agencies which studies winter maintenance products and strategies.

The Bonner County commission urged the state to cease using salt brine earlier this year until ITD completes research to verify whether the benefits outweigh the risks.

The state has embraced salt brine as an effective and less costly way of keeping roads clear.

But county commissioners and even some legislators contend there is a dark side to salt brine because it corrodes vehicles’ drive systems, electronics and brakes. The saline-based material also lures deer and moose to the highway.

State Sen. Shawn Keough, R-Sandpoint, said she would prefer the state ceased its use of brine immediately, but said some members of the public are pressuring ITD to keep using it.

“Our response, as legislators, is that ITD has a responsibility to weigh the costs of any deterioration in public safety that might occur because salt brine doesn’t work at some temperatures, and the costs to the public for the damage to their car from the corrosion,” she said.