Why NC lacquer fails on iron

This is one of the most common and most expensive substitutions we see. A workshop that finishes wood well starts taking metal work, reaches for the lacquer already on the shelf, and six months later the pieces come back.

Two separate failures

NC lacquer is oxidising. On a ferrous surface that is not a neutral property. It can actively contribute to rusting underneath the film, which means the coating you applied to protect the metal is part of the problem.

NC lacquer is hard, not flexible. Metal expands and contracts with temperature far more than timber does. A hard film on a moving substrate cracks, and once it cracks moisture reaches the metal directly.

Neither failure appears immediately. Both appear after the piece has shipped.

What to use instead

Iron needs an acrylic system. Lacquer 67 is our acrylic clear for metal and it behaves the way a metal coating should:

48 to 96 hours of 5 percent salt spray corrosion resistance
Flexible enough to move with the substrate without cracking or peeling
Fast drying, so it does not slow your production cycle
A smooth, even finish that enhances the appearance of the metal

It comes as a clear coat, a semi-mat and a mat, so you can match the sheen to the piece.

For heavier duty

Where the piece is going outdoors, or where it will take real abuse, move up to a direct-to-metal polyurethane. Metal PU gives exceptional resistance to wear, impact and abrasion, high corrosion and chemical resistance, good UV resistance for outdoor use, and enough flexibility to withstand substrate movement without cracking. Available high gloss, medium gloss, satin and mat.

And before any of it

None of this works over rust. If the iron has picked up surface rust in storage, clean it back first with a rust remover, lift the residue with a scotchbrite pad, and coat while the surface is still protected. Coating over rust traps the problem underneath, and it will come through.

The short version

NC belongs on wood. Acrylic and PU belong on metal. The cost of getting that wrong is not the coating, it is the container.