How to paint galvanized metal posts?

[wolive]

I have three galvanised metal 100x100 posts in my house that I would like to paint today. I have just painted the architraves and skirting using this product and they look great.

British Paints White Semi Gloss H2O Enamel Paint - 1L - Bunnings Australia

I'm hoping I can get these metal columns to look the same with the same semi-gloss white. However, I don't think I can paint this directly over bare galvanised metal. So, I'm wondering if I painted them first with something like this, could I then go over then with the H2O Enamel?

Dulux 500ML Metalshield RFU Etch Primer Grey - Bunnings Australia

The other option I thought of is using something like this, that doesn't require a primer. However, it is a gloss (not semi-gloss, which Bunnings doesn't seem to sell despite Dulux listing it as a product) and I don't know if the white is similar to the british paints white?

Dulux 500ML Metalshield Epoxy Enamel Gloss Paint Vivid White - Bunnings Australia

I've also just read that this product can be used on galvanised metal. I already have a tub of it and used it on the architrave and skirting before applying the H2O Enamel. So, does that mean I could just follow the exact same steps with the metal as if I'm painting wood?

British Paints White 4 In 1 Prep Water Based Primer Sealer Undercoat - 1L - Bunnings Australia

Does anyone have any experience or advice with painting galvanised metal?

[MitchellMc]

Hi @wolive,

The Metalshield primer is designed for Metalshield epoxy topcoats. For your posts, I'd recommend a standard primer that is suitable for galvanised steel, such as Dulux Max-adhesion. Then you can use your British Paints H2O Enamel over it.

Regarding your question on the Metalshield Gloss white, it will be a slightly different coloured white and shinier.

Please let me know if you have any questions.

Mitchell

[wolive]

So, do you think that the British Paints 4 In 1 Prep is not a good idea? I updated my post regarding it, so not sure you if saw that bit. The product says it is designed for metal, including galvanised metal.

[MitchellMc]

It will work @wolive, but it's not a specialised primer like the Max Adhesion. I'd do a test. Paint it on, wait a couple of days for it to cure, or several if it's wet in your location. Apply sticky tape to the primer and then rip it off. If it doesn't pull the primer off, then it should be fine.

Mitchell

[wolive]

I thought of that after I posted my question. I'll put some on today and report back my findings in case it is useful to other members later. Would you think a light hand sand to roughen the surface and/or a wipe down with white vineger to etch it a bit would be useful or a waste of time? Perhaps I'll try a few spots using these ideas and see what works or fails.

[MitchellMc]

Some experimentation never goes astray @wolive. My only concern is oxidation on the surface. Give the posts a good scrub down with some SugarSoap and a Scotch-Brite pad. Flush the SugarSoap off with fresh water and allow it to dry before priming.

Mitchell

[wolive]

So, 24 hours later and the British Paints 4 In 1 Prep held up fine on galvanised steel. I cleaned the steel with methylated spirits, then did four test patches, one with no further prep, one a light sand only, one a vinegar etch and one with both a light sand and a vinegar etch. I note on the paint tub it says to light sand smooth surfaces like steel for better adhesion. I then painted each section in both a thick and thin coat. I then used a fairly aggressive packing tape on it and let it sit on there for hours before pulling it off. All four test patches held up very well. In fact, the sticky stuff on the tape adhere so well to the paint, it delaminated from the tape in a number of spots (which I now have to clean off). Only a few small specks lifted off on the section that had no further prep work done. The other three only had tiny pin head size specs come off with the tape. The section that had been both lightly sanded and vinegar etched faired the best with virtually nothing coming off expect a few pin head sized specs. In addition, most specs that did pull off were from the side of the patch with the thicker coat of paint. So, a thin coat holds up better than a thick coat. I should also note that this steel is indoors and will not be exposed to the elements. So, whether or not sanding and etching galvanised steel in an outdoor setting is suitable or not, I'm not sure.

[MitchellMc]

Love your work @wolive and the depth you went to! Many thanks for the feedback.

Mitchell