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.
Purpose:
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)
Procedure:
PART A
- 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.
- 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).
- Bracket four arrived with a hot dipped galvanized coating.
- All four brackets were placed into the salt spray chamber vertically with the nuts and bolts end at the bottom.
- Brackets were removed after obvious corrosion had occurred. Please refer to photos.
PART B
- "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.
- After 960 hours, both panels were removed, rinsed, dried, and then examined for singes of corrosion. Please refer to "Q" panel photos.
Results:
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
- Corrosion occurs on brackets were moisture can pool. For example; lateral edges, drill holes, cracks, and crevasses. These areas can also be the most difficult areas to properly coat.
- Welded areas are also notorious for being high areas of corrosion, namely do to the metal stress caused by the process.
- VpCI™-374 adheres well to S/W if surface is free of dirt/oil residue as shown in photos below.
Conclusion:
- VpCI™-374 at 3.0 to 4.0 mils DFT* will give superior corrosion protection and should fulfill the requirements of the customer.
- Hot dipped galvanized-coated brackets give comparable to VpCI™-374 protection but at an increase financial and environmental price.
- Close attention should be paid to coating the edges, drill holes, weld areas, cracks, and crevasses to delay the onset of corrosion.
- Failure of the Sherwin Williams coating is do to the lack of corrosion inhibitors. Please refer to "Q" panel photos.
- 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