Application Notes

1. For long-term tests, or in particularly hostile environments, carefully clean the surface before applying any protective coating. Coating extending into uncleaned areas will eventually loosen.
    
2. When several layers of coating are required, extend each overcoat beyond the previous layer.
    
3. Incomplete protection around leadwires is a common cause of moisture penetration into gage installations. (Many commercial leadwire insulations contain pinholes.)
    
4. Seal wire splices with HST-1 Heat Shrinkable Tubing .
    
5. Before applying any protective coating to an unprotected installation which has been exposed to high humidity, dry the installation thoroughly.
    
6. If the coating is a room-temperature-curing type, the moisture absorption rate can be decreased by postcuring at an elevated temperature.
    
7. Generally, a thick coating offers a more resistant path to moisture absorption than a thin one.
    
8. For a further vapor barrier, apply an intermediate layer of metal foil (aluminum, such as M-Coat FA-2 , or stainless steel), or TFE Teflon film (first treated with TEC-1 Tetra-Etch compound for optimum bond). Since moisture can only penetrate around the edges of the foil or film, the path to the gage is much longer.
    
9. To evaluate protective coatings for long-term testing, monitor the zero-shift of the gage. Resistance-to-ground measurements can also indicate deterioration.

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