Products / Parker / Emi Shielding / CHO-SHIELD 2001 Series Corrosion-Resistant Conductive Coatings
The CHO-MASK II family of EMI foil tapes includes both Standard Tack (ST) and High Tack (HT) versions for providing a conductive, non-corroding surface on painted metal electronic enclosures.
Customer Value Proposition:
Parker Chomerics CHO-SHIELD® 2000 Series electrically conductive
coatings provide a corrosion resistant conductive surface coating on
aluminum or composite substrates.
By reducing moisture penetration, CHO-SHIELD 2000 Series coatings
offer corrosion protection for enclosure flanges which mate with
particular EMI shielding gaskets.
These tough, urethane coatings offer a highly conductive interface
which improves overall EMI shielding performance. When used as a
coating on a composite or other non-conductive surface, they provide
the conductivity necessary to achieve excellent shielding
effectiveness while maintaining their electrical and mechanical
stability in hostile environments.
CHO-SHIELD 2000-series coatings are three-part, copper- filled
urethane coating systems which have been formulated with special
additives and stabilizers to maintain their electrical stability
even at elevated temperatures which prevent aluminum surfaces from
corroding in high humidity and/or marine environments.
In addition, CHO-SHIELD 2001 and 2003 contain soluble chromates to
minimize the effects of galvanic corrosion of the aluminum
substrate, even in the event of a coating scratch.
Features and Benefits:
The CHO-SHIELD 2002 coating, mainly intended for composite
substrates or as a 2001 repair coating, is chromate-free.
CHO-SHIELD
2003 is a dark pigmented version of CHO- SHIELD 2001.
The CHO-SHIELD 2001 and 2003 coatings are designed to be used with
CHO-SHIELD 1091 primer on chromate conversion coated (MIL-DTL-5541
Type I, Class 3) aluminum substrates. CHO-SHIELD 2002 is designed to
be used with CHO-SHIELD 1091 primer on non-aluminum substrates such
as MIL-P-18177 glass-filled epoxy composites and will typically
deliver 0.1 ohm/square surface resistance when cured for 2 hours at
room temperature 21°C (70°F) followed by 30 minutes at 121°C
(250°F).
Three component urethane system
Corrosion resistant copper filler
Exceptional mechanical properties -65°C to 85°C (-85°F to 185°F)
including abrasion and scratch resistance.
Excellent chemical resistance, including jet fuel (JP8), hydraulic
fluids and motor oil.
Pre-measured kit allows easy mixing of components in one container.
Significantly more cost effective than silver filled epoxies.
Protects aluminum and graphite composite airframes from corrosion.
No degradation of shielding effectiveness after 500 hours of salt
fog.
CORROSION PROOF FLANGE DESIGN WITH CHO-SEAL® 1298 CONDUCTIVE
ELASTOMER, EMI SHIELDING GASKETS
The combination of the CHO-SHIELD 2000 series of conductive flange
coatings and CHOSEAL 1298 conductive elastomer gaskets can form a
virtual corrosion proof EMI sealing system for aluminum enclosures.
CHO-SEAL 1298 is a fluorosilicone elastomer filled with passivated
silver-plated aluminum filler. Figure1 shows this application for an
aluminum enclosure. First, the aluminum flange is typically treated
with a MIL-DTL-5541, Type I, Class 3, hexavalent chromate treatment,
or alternatively with Type II, Class 3, trivalent, chromate
corrosion treatment. Mask the middle area of the aluminum flange (
approximately half the gasket diameter width) where the CHO-SEAL
1298 conductive gasket will be attached. Apply CHO-SHIELD 1091
primer over the treated aluminum to ensure proper adhesion of the
CHO-SHIELD 2000 Series coatings. After allowing the CHO-SHIELD 091
to dry properly, apply the CHO-SHIELD 2000 series coating according
to the instructions contained below in this document. The CHO-SHIELD
2000 coating is then masked while the non-conductive topcoat is
applied to the aluminum enclosure. However, note that the topcoat
must be overlapped onto the CHO-SHIELD coating as shown in Figure 1
to ensure that the CHO-SHIELD coating and aluminum interface is not
exposed to moisture that could intrude under the coating. Note also
in that when choosing a topcoat, that that the maximum temperature
for the CHO-SHIELD 2000 coatings is 85ºC.
Application
Surface preparation has a significant impact on the corrosion
resistance offered by the CHO-SHIELD 2000-series of coatings.
CHOSHIELD 1091 primer should be used to ensure good adhesion of
CHO-SHIELD 2000-series coatings on all substrates. CHO-SHIELD 1091
primer is a one-component, air-drying system,which cures at ambient
temperatures.