Painting on metal: a few tips for the paint to stick!


Increasing the adhesion of paint on metal

There are different kinds of exterior metallic sidings which ask for different metal paint and techniques for the result to be not only perfect, but durable in the long-term.

Types of metal sidings

In Quebec, the most commons are:

  • aluminum
  • steel
  • iron
  • galvanized zinc

And decorative parts, such as:

  • lintels
  • curtain-walls
  • steeldecks
  • wrought iron balconies and racks

Start with a pressure washing

Being the first crucial step to take before any task of metal painting, pressure washing allows you to save time and greatly increases finish quality.

After this first grinding, the applied paint adheres much better. Pressure washing is precise and particularly efficient on metal surfaces if the pressure used is big enough.

Among other things, pressure washing allows you to find out if some parts of the surface are rusty or if they will need to be changed eventually or before the application of paint or rustproof treatment.

Metal cornices can be grinded, washed and painted the same day as metal dries really fast under the sun.

A few tips and tricks

Sanding is recommended between each coat to ensure a smooth finish.

The paint must be applied in the shadows, as the sun rays could cook the paint on the metal before it dries. During frost, it’s important that the exterior temperature doesn’t go below 4°C not only during application, but also for the required drying time, which is at least 5 hours after the application.

If the paint is applied using a sprayer gun, it’s recommended to use an elevation lift instead of a ladder or scaffoldings. This is a lot safer as the painter won’t have to hold the gun (sometimes quite heavy) and the ladder at the same time. The work quality will also be increased.

Painting aluminum sidings

Aluminum sidings (aluminum sheets) are found everywhere in Montreal, especially on:

  • garage doors
  • exterior walls of warehouses and commercial buildings
  • roofs
  • flashings
  • soffits
  • columns
  • banisters
  • balconies
  • staircases
  • shutters
  • gutters

the best choice is a paint conceived for exterior use which will resist to Quebec’s changing climatic conditions and adhere properly to metal.

The spray paint gun allows for the application of a smooth and even coat with a perfect thickness.

Steel and iron sidings

The main problem is rust. In the case of important damage, some parts could be replaced. Before applying the paint on metal, the rust which is only on the superior surface should be treated:

  • mechanically (electrical grinder, manual or electric sanding, scraping)
  • chemically (rust annihilator, rust converter)
  • with specially conceived coatings (rust retardant, inhibitor primer)

Then, rust inhibitor paints are preferred to apply on the treated surface.

If the metallic surface doesn’t show signs or rust and that only a color change is needed, you have several options for the paint choice:

  • DTM (direct to metal)
  • urethanes
  • acrylics
  • alkyds
  • epoxys

Galvanized metals

Less and less used for exteriors because of their lack of beauty, galvanized metals (with zinc) are still present in our city.

This alloy’s composition generates what is commonly called ‘zinc soap’, which is a greasy film continually regenerated on the surface and greatly decreases adhesion. This is why the material has to be cleaned with an industrial degreaser before applying a primer for galvanized metal and paint.


Popular for commercial surfaces, steeldecks allow for the use of dryfall. This coating does not ask for any particular preparation and the paint used offers the advantage that the paint surplus becomes dust that can be swept away with a broom, this is why we call it dryfall. Moreover, dryfall is interesting for low-budgets.