We blast steel down to clean metal

Good paint starts with a good blast

Sandblasting fires abrasive at steel under air pressure until the rust and old paint are gone and the metal underneath is clean and bare. It does a second job at the same time. The blast leaves the surface slightly rough, which you can feel if you run a fingertip across it. New primer grips into that roughness. Paint put on smooth or rusty steel has much less to hold, and it starts to lift at the first scratch or chip.

On a typical job the order goes like this. Anything that must not be blasted gets masked or taken off first, like rubber seals or the smooth machined face on a shaft. Then the steel is blasted one section at a time until the whole surface is an even gray with no old paint left. After that the dust is blown off, and the steel is checked for rust hiding in pits and seams before any primer goes on.

Skip the blast and the failure shows up later, often within a winter or two. Paint over rust seals moisture and salt in with it. The rust keeps growing under the paint and pushes up blisters. Then the coating comes off in sheets with orange steel underneath. Wire wheels and grinders help on small spots, but they tend to smooth rust over instead of taking it out. They also cannot reach the bottom of a pit.

• Paint and rust looked at before we quote
• Seals and machined parts masked before blasting
• Rust and old coatings taken to bare metal
• Dust blown off and pits checked for rust
• Blasting in our shop or at your site

Humid weather puts rust back on steel

Freshly blasted steel is the most exposed it will ever be. There is nothing on it but clean metal, and clean metal reacts with damp air. On a muggy central Illinois summer day, a thin orange film called flash rust can form across a blasted surface within hours. Primer put over flash rust is sitting on a loose layer again, which undoes the whole point of blasting.

That is why the gap between blasting and priming should be short. Our paint shop is temperature controlled, so blasting and priming happen in steady conditions instead of whatever the weather is doing that day. The steel also has to be warmer than the dew point. If it is colder, a film of water you cannot see forms on it, and the primer goes on over that water. A part hauled in cold on a January morning gets time to warm up first.

Winter brings road salt. Equipment that runs on salted roads carries salt in every seam and pit, and salt left on steel keeps pulling moisture in under new paint. Blasting alone does not always get it out of deep pits, so a salty part gets pressure washed with clean water before it is blasted. Freezing and thawing make the damage spread faster. Water that gets under the edge of the paint freezes and lifts it a little more each cold snap.

Farm steel rusts in the same spots

Montgomery County is farm country, and a lot of the steel around Fillmore is farm steel. That means the beams and columns inside machine sheds, along with the legs and ladders on grain bins. That steel rusts in the same two places every time. The first is the bottom, where mud and standing water sit. The second is any joint where two pieces of metal overlap and trap moisture between them.

Those spots take the most care during blasting. Rust between two overlapping plates packs in tight and swells, so the blast has to be aimed into the seam from more than one side. Pitted steel at the base of a column needs slow, close work, because rust sits at the bottom of every pit. If a pit is left brown, the new coating fails there first, even when the rest of the steel looks perfect.

Not every surface around here should get a full blast. Most grain bins are galvanized, which means the steel carries a coat of zinc that protects it from rust. That zinc should stay. The right blast on galvanized steel is a light pass that roughens the zinc for primer without stripping it away. Soft old brick and the wood siding on older farmhouses are a different case. A hard abrasive blast cuts into both and leaves them worse than it found them.

We sandblast in the shop or onsite

Steel that fits on a trailer can be hauled to our shop in Fillmore and blasted indoors. That is the better setup when it is possible. The weather stays outside, and the part can be turned so the blast reaches every side, including the underside that sat on the ground. Primer can go on in the same temperature controlled building soon after blasting, before the bare metal picks up moisture from the outside air.

Some steel cannot move, like the beams inside a working building or a machine too big to haul. That steel gets blasted where it stands, on your site. Blasting on site takes more setup. The area around the steel has to be covered or closed off so abrasive and old paint dust do not land on everything nearby. The work also has to follow the weather, so blasting and priming get planned around dry hours instead of the calendar.

Abrasive is not the only way to strip steel. Water jetting takes coatings off with very high pressure water instead of grit. It makes sense where blast dust would cause trouble, like inside a building still in use or next to running machinery. Water does not roughen the steel the way abrasive does, so the coating that follows has to suit a smoother surface. We will tell you which method fits your steel at the free estimate.