Rust, aged copper and metallic finishes for walls, columns, railings and business premises on the Costa del Sol. Two very different things are sold under the same name: a rust that comes from a chemical reaction on the wall itself, and a paint with aluminium that imitates metal. Here is how they differ, what goes wrong with each and where each one fits.
What all decorative finishes have in common — the light, the sample, one wall rather than four — is on the decorative painting page.
Before looking at colours, you need to know which of the two you are being offered, because they are not applied the same way, not protected the same way and they do not age the same way.
A water-based paint containing real iron particles and, on top, an activator: an acid solution that reacts with that iron and makes it rust. The rust is not painted on; it appears. That is why the result depends on how it is applied, and why it has to be sealed once it reaches the shade you are after: otherwise the reaction carries on. The same system comes in copper and bronze versions, with green or blue patinas.
An acrylic paint with aluminium that gives the wall the satin sheen of metal. There is no reaction: what goes on is what stays. It is tinted silver, gold, bronze, graphite or in colours, and the difficulty lies not in the chemistry but in the hand: any stroke in a different direction shows.
Inside, from the bottom up
Sold together, and nothing alike
Real rust
A reaction that is triggered, then sealed
Metallic
A paint with aluminium
The layers are the ones their data sheets ask for; the thicknesses in the drawing are not to scale.
If what draws you is the sheen but with texture, some sand paints carry metallic glints; we cover them on the sand-effect page.
The two finishes fail in different places: rust through the chemistry, metallic paint through the hand. What follows comes from their data sheets.
The activator is acidic, and if it gets through the paint it reaches whatever is behind. That is why the data sheet asks for a blocking primer over metal that can rust, reinforced concrete and dense timber: without it, the acid reaches the surface underneath and draws out rust or tannins where nobody wanted them. On a reinforced concrete facade, that is exactly what must not happen.
That is how the reactive system’s own data sheet puts it for the sealer: indoors, recommended; outdoors, essential. Its job is to stop further oxidation, and the sheet also asks for no rain in the three days after it is applied, because moisture affects it while it dries.
The aluminium reflects light according to which way it has settled, which is why the data sheet asks for it always to be applied in the same direction: otherwise lap marks and patches of light and shade appear. If what you want is exactly the opposite, an uneven finish, the same sheet suggests a wool mitt, a rag roller or a sponge.
Depending on how the activator is applied, the finish comes out even or not: the data sheet says so in as many words. Sprayed from the bottom up it looks more organic, and from the top down, streaked. And cold and damp slow down both the rusting and the drying, so in winter you have to allow for more waiting.
None of them is put right with another coat on top. A badly sealed rust or a metallic finish with lap marks is redone across the whole section of wall.
The wall behind the sofa, a column, a beam, the front of a bar in a shop or restaurant. Rust and metal want to take centre stage, and they work best when what surrounds them is plain. Indoors, sealing the rust is recommended; in an area that gets rubbed against, it is worth doing.
Railings, doors, a garden wall, planters: the reactive system is also used outdoors, always sealed. Metallic paint can be used outside, and in very exposed spots its data sheet recommends a coat of varnish on top. One of the iron paint data sheets, on the other hand, states it is for interiors only: you need to check which one it is.
The green of aged copper comes from the same idea: a paint with copper and an acid patina on top. Unlike rust, the data sheet does not ask for it to be sealed in most cases, only when it will be touched a lot or will be out in harsh weather.
“Rust effect” is used for both. To be able to compare offers, each quote needs to make clear whether it is a reactive paint with an activator or a rust-coloured or metallic paint, how many coats it gets and what it is sealed with. They are different jobs and they do not cost the same.
The metallic paint’s data sheet asks for it to be applied with the relative humidity below 70%. In Málaga, average humidity from October to February is between 70 and 72%, according to the climate table in the CTE (the Spanish Building Code, Código Técnico de la Edificación). It can be done, but by choosing the hours and the day, not whichever comes first.
Because it comes from a reaction, the shade is not picked from a colour chart: you watch it appear and seal it when it is right. That means that, with this finish, the sample is not a formality. And that on the day of the job someone has to be there to decide when to stop.
It depends on what you are offered. With a reactive paint, yes: it contains iron and an acid activator rusts it on the wall itself. With a rust-coloured or metallic paint, no: it is the look, with no reaction. Both are legitimate, but it is worth knowing which one it is before you pay.
Freshly made rust can shed dust: that is why, when real metal is rusted, the data sheet asks for it to be washed thoroughly before sealing. What fixes it is the sealer, which forms a film over the rust. Indoors it is recommended and, in an area where people lean, it is worth applying.
With the iron paint and its activator you get real rust on a masonry wall, which is the look of Corten steel, without any metal underneath. And if what you have is a genuine piece of Corten steel, the data sheet allows the activator to go directly on it, thoroughly cleaned.
The reactive system is stated for interior and exterior use, and outdoors sealing is essential. On a reinforced concrete facade, the blocking primer comes first as well: the acid must not reach the reinforcing steel. For a whole section of facade, the sensible thing is to do a sample outside first and watch it for a while.
We do not give a price per metre without seeing the wall. It involves more steps than paint — primer, several coats, activator, waiting and sealing — and what weighs most is the labour. First we see the wall and decide which of the two finishes it is; then we give a fixed price.
Send us a photo of the spot, tell us whether it is indoors or outdoors and what the surface underneath is made of. With that we can tell you which of the two finishes fits, what protection it needs and how to approach the sample.