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Rust spots appearing through paint on NEW steel entry doors again!

I installed a new pair of 4X7 steel entry doors on my shop which I purchased from a local supplier. They came pre-primed. After cleaning the doors well I applied an additional coat of 100% acrylic primer and two coats of exterior latex paint. Rust spots began appearing through the paint within a few weeks.

Perhaps rusty metal was primed over at the fabricators or I didn't notice a light rusting of the metal before I began painting. Thinking that I should have applied an additional coat of rust inhibiting primer in the first place, I stripped the doors with Jasco ⇦ this on eBay or Amazon [affil links] , sanded them well, mostly down to bare metal and a bit of the origional grey primer. I then coated the doors with rustolium oil based primer, waited 24 hours and repainted with two coats of exterior latex. WITHIN ONE WEEK I NOTICED RUST SPOTS APPEARING THROUGH THE PAINT AGAIN! What am I doing wrong? Next time use two coats or primer? Avoid latex paints? Prep differently? Use epoxy? The doors are protected by an ample awning. I am befuddled.

James Thornton
remodeling contractor - Oakland, California, USA
2007

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2007

What will help here is a Corrosion Preventative Compound using Fluid Thin Film Coating Technology.

thin clear liquid, wipe on with a rag, it will penetrate under the paint through the holes and prevent rusting under the paint. It may need re application every 6 months but only takes a minute.

Contact me off the forum for where you can purchase this product.

Terry Laing
- Victoria, British Columbia, Canada

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Hello JAMES,

Neutralise the metal surface after stripping.
Clean up with Isopropanol (use strong paper towels) after sandblasting.
Avoid acrylic paints. Use an epoxy or urethane.
Let me know.

Jose Castellanos
- Minneapolis, MN, USA
2007

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Are these doors like a steel box? If they are they are rusting from the inside, nothing that you do to the outside is going to prevent it. Acrylic latex is used on wood.

Sheldon Taylor
supply chain electronics
Wake Forest, North Carolina
2007