Paint Approval Considerations 1

[macoovacany]

What type of engineering considerations (corrosion prevention, electrical conductivity,...(?) ) needs to be made when approving particular painting materials, e.g. paint stripper, filler, primer, topcoat, etc.

1) Story going around of a private owner who used automotive wax for buffing his a/c. Unfortunately, this contained a silicate which played havoc with the aircraft radio systems. Aircraft eventually had to be completely paint stripped and repainted.

2) The current batch of commercial paint strippers are acidic*, where as the paint strippers used in aircraft standard practices are basic*. A problem we found with the commercial paint strippers is that they would remove the Cad plating of the aircraft hardware. Apart from this**, there appears to be no reason not to use the commercial paint strippers.

DO NOT SAY: "Follow the aircraft manufacturers instructions." Often the only painting material approved by the aircraft manufacturer is of paint materials no longer available or exceeding difficult to source.

Regards,
Timbo

*Might be the other way around

** Instructions: "Remove all cad-plated hardware prior to paint strippin

 

[CRACKKILZ]

Depending on the aircraft type and utilization there are many things one should consider.

A few that come to mind are listed below -

Commerical Stripper issues:

1. Hydrogen embrittlement of high strength steel parts such as the langding gear etc.
2. Possible damage to composite parts
3. Possible damage to fillet seals and possibly fay surface seals at joints. Possible damage to antenna gaskets/seals etc.
4. Effect on flame sprayed parts? (This is related to electrical bonding of panels)

Primer issues:

1. Hydraulic/fuel resistance required?
2. Adhesion performance with various conversion coatings
3. Compatability with topcoats - e.g polyurethane compatible primer to be used with polyurethane etc.
4. Corrosion resistance
5. Effect on radome transmissivity (sp)

Paints:

1. Erosion prone area ??
2. UV exposure
3. Fluid resistance etc

In addition there are many environmental issues including disposal of strippers and application of heavily chromated primers.

I am sure there are many other engineering considerations, it just depends how on how deep you want to investigate this and what type of airplane you are working on.

I assume you are working on a gen av. product and as such some of the issues mentioned above may not apply.