Dry ice blasting

Need to know

Time: 2 hours.
Cost: See below.
Difficulty: 5 out of 5
Models: All Land Rovers.
Tools needed: Blasting equipment, compressor, safety PPE.
Work safely:
• This is a professional process, not DIY. The operator will advise on all safety requirements that might affect the owner.
• Basically, keep clear of the equipment and work area, given the dangers of compressed air, airborne particles and the possibility of cold burns from iced equipment.thanks to: Tom Balfour-Smith ([email protected]) and Twenty Ten Engineering .twentytenengineering.co.uk.

 

In owning or restoring a Land Rover, we all have a need to clean parts or areas of the vehicle sooner or later, removing oil, wax, ingrained dirt and other contaminants. There are a number of processes to achieve that, either chemically or physically. But what are the different processes, and what are the strengths of each? In this occasional series, LRM looks at various methods to clean components, to help you choose what technique is right for which parts restoration. In this first feature, we look at dry ice blasting.

Blast-cleaning involves a blast media being fired, using compressed air, at the surface of the part, physically shocking off contaminants, loose paint or corrosion to produce a clean surface. Dry ice blasting uses frozen carbon dioxide (CO²)  pellets at -78.5°C as the cleaning medium. Carbon dioxide is normally a gas but, when chilled to a very low temperature, becomes a solid, sometimes known as dry ice, and lends itself superbly as a blast medium.

The process works in a combined way. When the frozen pellet, fired under pressure, hits the surface being cleaned it does three things. First, the CO² pellet hits the surface, physically shocking contaminants away. Secondly, the pellet then sublimates – or changes from a solid back to a gas. As it does this, the gas expands, which itself gives a lifting action, to raise contaminants off the surface. Thirdly, there is the effect of the air pressure, which also drives off dirt.

One specialist who offers the service is Tom Balfour-Smith, The Blast Smith, as his business is known. The mobile specialist offers dry ice blasting all over the UK for automotive and restoration purposes. We saw him demonstrate the process in cleaning the engine bay of a 1971 Range Rover at Twenty Ten Engineering in Redditch.

“Because it is called blasting, people think it is for rust removal,” he explains. “It is a cleaning process primarily,” he points out. “It can’t clean up a neglected car, one where corrosion has already bedded in, but it’s best on ‘survivors’, or cars in nice, original condition.”

To get the most from any process we have to understand its strengths. Because it is non-abrasive, it won’t remove rust, nor will it strip paint. Corrosion or paint removal requires an abrasive process. The only rust or paint CO² blasting will remove is already loose flakes. Dry ice blasting’s forte is removing surface contaminants, without leaving a mark on what is underneath, regardless of the surface type: paint, steel, aluminium, plastic or rubber.

There are no chemicals nor moisture left, so it is safe on wiring, too. “If you have a genuine, original vehicle, where it isn’t worth taking apart to clean everything, this process is perfect,” explains Tom.

It isn’t, then, a process to commission if you’re beginning a restoration of a Land Rover with heavy corrosion – say, the chassis of an early 90 or Range Rover Classic that has been off the road a decade or so. Instead, it is a process to consider if you have an original car you want to lift to the next level of originality, for example by cleaning areas without damaging patina, or the original finish. Such as the engine bay of the Range Rover we’re looking at here.

The cost for an engine bay is around £200 at the current ice and fuel prices, but each job and car is different. Contact Tom for a quote at [email protected].

 

How it's done

The start: This engine bay is 50-years old, complete, and typical of a Range Rover with years of built-up and ingrained dirt, most obvious on the washer bottle.

Easy win: Tom points out a few areas he expects the blasting to noticeably improve. This plastic washer bottle is typical; ingrained dirt and wax that never wants to scrub off.

Alloys, also: Tom says aluminium parts, carburettors, intake manifolds, rocker covers, also will benefit. Again, aggressive chemicals are the usual go-to, but that means lots of liquid, too.

Mix of materials: He suggests this brake servo may be trickier due to the corrosion. Surface rust, wax overspray, and a number of different materials offer a challenge, at the very least.

Raw material: Tom carries the blast media in polystyrene boxes. It isn’t a cheap media, so he carefully meters the usage to balance results against excessive media consumption.

Load up the machine: The pellets are loaded into the blast machine, which in turn is hooked up to a large compressor. Notice the familiar fog we recognise as dry ice, sometimes used in nightclubs and at parties.

Lance: This is the lance used to direct the media at the target components. Pellets come in 1mm, 3mm and 12mm sizes. Tom favours 3mm, but uses a blaster nozzle to break it right down.

Blasting begins: This is the process at work. Nothing to see but a light mist. It is very loud procedure, though, though thanks to the compressor. Hearing, eye protection and a mask are used.

What happens next: When the media fires out, it hits the surface and sublimates, turning back into a gas. It literally disappears before your eyes. No water, nor blast media is left.

Work the angles: Tom patiently works the area, aiming the lance at each detail section in turn, working carefully to access each face and area as needed. It is steady, methodical work.

On the move: He is always moving, so as to get into all the corners of each component or area. The media flow is started and stopped, so he’s only cleaning when he needs to.

Complex corners: On complex areas, such as the carb and intake, Tom comes at it from each side. The working distance is varied, with varying media pressure to suit the cleaning needed.

Tricky bit? Moving to the other side, he works the lance over the brake servo. Again, he’s always on the move, working various angles, and almost delicate in his precision.

Details matter: Small parts are rotated, such as the top on the brake fluid reservoir, so as to clean every last crease of the component. Plastic parts clean up particularly well.

Another lap: Tom doesn’t just do one side, and then the other; instead, he finds it more efficient to work diligently in one area, move on, then return, working more angles and corners.

Delicate work: Even the wiring harness is cleaned, revealing the wiring colours as if they were new. You would never manage this level of scrubbing with water or chemical cleaning.

Reload, reload: After an hour of steady work the hopper is reloaded with more dry ice. Typical consumption is around 20kg per hour of CO² pellets, but every job works out differently.

Check, work, check, work: Tom hones in on any areas he spots he has missed, or needs to work further. It is a steady process, working methodically and diligently, still continually on the move.

Life below zero: Notice the lance barrel icing up from the media passing through it. It quickly thaws, but it’s a reminder that the material we are working with here is at -78.5°C.

Blaster nozzle: This is the blaster nozzle, which breaks up the 3mm pellets further, into dust. This avoids the theoretical risk of pitting aluminium parts. Although small, the risk is possible.

Second pair of eyes: It can be hard to see the bigger picture when you’re so closely focused, so Tom asks Twenty Ten boss, Phil, to have a look. A second set of eyes is always useful.

Dark corners: The last few corners are given a tickle, such as around this fixing screw for the washer reservoir. Note how no paint is removed. It isn’t an abrasive process.

Stripping out: For better access, the air filters are removed, so Tom can get in a few extra gaps. The bulkhead isn’t cleaned, to avoid risking removing any old, flaking paint.

Big reveal: The end result. One clean engine bay. Note the extra colours revealed from where we started. Materials look as new, but it is the same 50-year old car.

Check back: Checking on the areas Tom highlighted, first the reservoir, which looks like a new part. So too, does the bulkhead behind it, looking beautifully patinated and original.

Carbs: The carbs have cleaned up, too. No amount of jet washing, heat, nor scrubbing would have given this result. Hoses, clips and gaskets are also spotless once more.

Verdict? The brake servo cleaned up very well. There is some light corrosion, but all the wax and ingrained dirt came straight off, even in the crevices of the fluid reservoir.

 

“I use it” – Phil Holland, Twenty Ten Engineering

The last time you saw such a clean P38A, it was 1999

Twenty Ten boss Phil is well respected in the Range Rover restoration world, producing enviable full restorations of Classics, but also servicing and modifying them, too. Today he booked Tom to clean the engine bay of a customer’s 1971 Range Rover.

“Dry ice blasting is great on engines, gearboxes, and especially the stuff which sticks to engine bays,” says Phil.  He usually sets Tom up outside, but theoretically, the process would be possible inside, because of the lack of contaminants during and after the process. Noise from the compressor is the main reason for the outside working.

“It saves us stripping things to clean; it just looks fantastic afterwards,” he tells LRM, as we stand next to his immaculate P38A that had the engine bay cleaned six months ago. “No amount of jet washing would get it like this, before you consider the heat needed or volume of water,” says Phil. “The difference in real life is obvious, more than in pictures,” he enthuses.

 

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