Painting galvanized pipe

A. An earlier visitor to the site reported that cleaning with a scrub brush [on eBay or Amazon] and trisodium phosphate [on eBay or Amazon] took care of the prep work. Then you just paint it with a Self-etching primer [on eBay or Amazon] . This assumes you are talking about a consumer application! A manufacturer who is making painted galvanized pipe should be careful to make sure that the pipe is not chromated after galvanizing, but is zinc phosphated and immediately painted instead. Visit www.galvanizeit.org to learn more.

A. The reason you get conflicting answers, Philip, is that painting galvanized materials is a difficult problem but no one is going to say it's impossible, because it's not; plus no one can say what's "good enough" for you.

If you are selling a product made from this galvanized pipe it's one thing; if you're just trying to scrape by with a personal project, it's another. But for personal use get a primer made for the application like Bulldog Tie Coat [affil links] and you should be okay. Good luck!

A. Hi Muhammad.

The "right" way to paint most galvanized surfaces is to first send them through a zinc phosphatization pretreatment line. Where this is not possible, for example on fieldwork repairs, scrubbing the area with a detergent like TSP, rinsing it, wiping it with diluted vinegar [in bulk on eBay or Amazon], then priming with a self-etching latex primer is probably the way to go.

Regards,

A. Galvanized substrates that not intended to be painted are usually passivized. You need to remove this thin layer of passivization before you can paint over it.

We occasionally get passivized coils, usually from one of our customers for a price to good to be true. A quick pass through the EG line removes the passivization before we paint.

Q. No significant difference except perhaps in texture of the finish, and that dependent on the thickness (viscosity) of the paint at application.
If the paint is quite fluid, then brush painting should flow OK leaving a uniform coat without significant brush marks. User ability (skill) is required in how to brush the surface to minimize brushing marks.
Spraying might give a better finish, but also requires operator skill. Overspray can cause runs where excess is applied, and undercoating (thin) is easier to do my mistake in spraying.
If finish is critical, then consider multiple coat system.