Chassis coating sheen advice

[erover82]

I'm coating a galvanized chassis and plan on using SPI's epoxy since I understand it is self-etching and should adhere well. I've had good luck with it in the past on zinc plated parts. However, the epoxy is more glossy than I would prefer for this chassis, otherwise I would just use several coats of epoxy and call it good. Another issue is this classic Land Rover has a few permanently exposed chassis sections that could see a lot of UV. Is a final coat of single stage with a flattening agent (don't see that SPI offers one though) my best option for a satin-semigloss UV-resistant chassis coating solution? I'm open to ideas.

Thanks

 

[crashtech]

SPI #2201 Matte Black would be an excellent choice for what you are doing. If it was mine to do, I would apply 2 full coats of unreduced black epoxy, then the next day, apply 2 coats of the Matte Black. Page 17 of the SPI Tech manual has the details.

 

[erover82]

SPI #2201 Matte Black would be an excellent choice for what you are doing. If it was mine to do, I would apply 2 full coats of unreduced black epoxy, then the next day, apply 2 coats of the Matte Black. Page 17 of the SPI Tech manual has the details.

I saw the Matte Black product but didn't see that its sheen was adjustable by mixing ratio. Thanks

 

[Chris_Hamilton]

I'm coating a galvanized chassis and plan on using SPI's epoxy since I understand it is self-etching and should adhere well.

It is not self etching. The surface needs to be properly prepared. Bare or galvanized, especially galvanized you need to have 80 grit machine (DA/Orbital) scratches or the equivalent (hand sanding) on the metal for maximum adhesion. If you do not sand that glavanized surface you can expect to have adhesion issues.

 

[anotheridiot]

yeah, galvanized is the hardest stuff to cover because galvanized metal has the whole purpose of protecting that metal from anything sticking to it, which causes any corrosion to not stick to it, so it is very difficult to make paint stick to it. If its glossy galvanized you will not find anything to dig in. Etching only has to do with bare metal, shiny outdoor stuff sheds corrosion easier.

 

[crashtech]

Zinc oxidizes rapidly in air, and forms various chemical compounds that ultimately serve to protect itself against further corrosion. Aluminum is another example of a metal that swiftly forms an oxide layer that protects itself.

There are many reasons why there are adhesion failures when painting over zinc. I dug up an old article that has some interesting information on the properties of zinc coatings as they relate to refinishing.

Painting_Galvanized_Steel_Malone.pdf

drive.google.com

 

[anotheridiot]

one of the specs I need to follow is for NASA. NASA-STD-5008. You can google that and see what they require. Florida is all Galvanized happy for corrosion protection, so when I started painting these nasa parts, they needed us to use a red oxide primer, followed by a zinc primer. You got a gallon can of zinc dust, mixed it in part B of the paint until it turned into a sludge, then thinned it out to be able to spray it thru a good old binks number 7, but better to be rolled on.

Galvanized, aluminum, even stainless steel all work against paints. Zinc plating is great on steel, just needs epoxy, that is on any spec where flat surfaces are required to be masked for grounding purposes. But hot dip zinc galvanizing is far away from the pristine coating if zinc plating. Galvanized is a finish coating, you are eventually going to be disappointed. If its just some cold zinc paint coating, get rid of it if you are changing the protection to epoxy and paint.