VpCI™-374 on ADC Brackets

Background: ADC has brackets that fasten electronic equipment to outdoor surfaces. These brackets are currently coated with a Sherwin Williams (S/W) solvent-based product. These brackets are corroding prematurely. ADC wishes to get five years corrosion protection from their brackets. They are looking into a hot dipped galvanized method but would prefer to go with an environmentally friendly method. ADC also has several hundred brackets (coated with S/W paint, in inventory) that need additional corrosion protection to be field ready.


1) Determine salt spray protection of various coatings on brackets provided by ADC.

2) Determine if VpCI™-374 can be top coated over Sherwin Williams paint to improve corrosion protection.

Materials: VpCI™-374 primer

VpCI™-432 paint stripper

VpCI™-414 cleaner/degreaser

3x5 inch brushed carbon steel "Q" panels

Elektro-Physik N Koln Minitester 500 Thickness Gauge

Adhesion testing tape "Permacel"

Razor blades

Method: Salt spray Chamber (ASTM B-117)

Tape Pull-Off Adhesion Test (ASTM D-3359)



    1. Four brackets were received from ADC. One of the parts was stripped to bare metal using VpCI™-432 paint remover, then cleaned with VpCI™-414, rinsed, dried, and coated with VpCI™-374.
    2. Two of the parts received were coated with Sherwin Williams’s gray primer. One of these two pieces was washed in VpCI™-414 cleaner/degreaser; water rinsed, dried, then top coated with VpCI™-374. Adhesion tests were preformed on the Sherwin Williams/VpCI™-374 coated bracket before and after the VpCI™-414 cleaner/degreaser. (Please, refer to photo below and the result section).
  1. Bracket four arrived with a hot dipped galvanized coating.
  2. All four brackets were placed into the salt spray chamber vertically with the nuts and bolts end at the bottom.
  3. Brackets were removed after obvious corrosion had occurred. Please refer to photos.


    1. "Q" panels were coated with either VpCI™-374 or Sherwin Williams (S/W) at 2 mils DFT, allowed to dry properly and placed into the salt spray cabinet.
    2. After 960 hours, both panels were removed, rinsed, dried, and then examined for singes of corrosion. Please refer to "Q" panel photos.


Coating (BRACKETS) Thickness (DFT)* Salt spray (Hours)

Sherwin Williams (SW) 0.8 to 1.5 mils 270

SW/VpCI™-374 4.0 to 6.0 mils 674

VpCI™-374 2.8 to 5.0 mils 840

Galvanized 4.0 to 6.0 mils 840

Coating ("Q" panels) Thickness (DFT)* Salt spray (960 Hours)

VpCI™-374 2.0 to 2.0 mils PASS

SW 2.0 to 2.1 mils FAIL

Tape Pull-Off Adhesion Test on brackets (S/W top coated with VpCI™-374).

5-B = best adhesion and 0-B = worst adhesion.

With VpCI™-414 cleaning (5-B to 4-B) PASS

Without cleaning (1-B to 0-B) FAIL


    1. VpCI™-374 at 3.0 to 4.0 mils DFT* will give superior corrosion protection and should fulfill the requirements of the customer.
    2. Hot dipped galvanized-coated brackets give comparable to VpCI™-374 protection but at an increase financial and environmental price.
    3. Close attention should be paid to coating the edges, drill holes, weld areas, cracks, and crevasses to delay the onset of corrosion.
  1. Failure of the Sherwin Williams coating is do to the lack of corrosion inhibitors. Please refer to "Q" panel photos.
  2. Current S/W coated brackets in inventory, can be top coated with VpCI™-374 if properly cleaned and dried before applying topcoat. VpCI™-414 cleaner/degreaser is recommended.

*Dry Film Thickness (DFT) was measured in mils (1 mil = 1/1,000 of an inch and 1 mil = 25 microns).

Project #: 01-257-1525

Time Spent on Project: 16 Hours

To: Richard Atlas/AEI

For: ADC

From: Luc Butzon

Date: 10-31-01

cc: Boris Miksic

Anna Vignetti

Rita Kharshan

Cliff Cracauer

Art Ahlbrecht

Vanessa Schultz



960 Hours Salt Spray

No pre-cleaning. Poor adhesion of VpCI™-374 to Sherwin Williams Coating

0-B 1-B




Pre-cleaning with VpCI™-414 at 10%, water rinse, dry. Sherwin Williams top coated with VpCI™-374. Excellent adhesion.

4-B 5-B





Salt Spray