Metal Cleaning.

Surface Preparation – Nationwide

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Sand Jet Cleaning of Metal

We specialise in using a low pressure sand jetting system but obviously sometimes traditional sand/bead blasting is more appropriate for metal cleaning.

However The ‘damp’ system also captures dirt and abrasive, preventing the health and safety risks associated with dry blasting. So for instance we can safely deal with lead based paints – as in the case with the building on the right.

It also acts as a coolant, and therefore can clean thin metals, such as steel motor vehicle shells, without heating the surface causing distortion. In particular though this capturing of dirt means that the system can safely clean lead based paints from structural steelwork ad Cast Iron . It is also ‘soft’ enough to clean Aluminium or Alloy surfaces without heavy scratching – but enough profile to allow paint coats to fully bind to the cleaned surface.

A further advantage of the system we use is that it also uses far less abrasive than traditional sandblasting, making expensive abrasives, such as garnet, cost effective, and more significantly reducing waste. Abrasive does not need to be recycled, preventing cross contamination between jobs, and apart from in specialist cases, is not a major part of the running costs.

Grit or Sand Basting Metal

While we specialise in using the damp sand jetting system sometimes traditional sand/bead blasting is more appropriate for metal cleaning.

Traditional grit blasting tends to be more aggressive – and therefore is probably a little quicker – but considerably more dusty.   The surface, if exposed to any moisture, will also flash rust rapidly. But- on the whole a surface that has been dry grit blasted is likely to be easier to paint than one which has been damp blasted – unless the paints are moisture and / or flash rust tolerant. One regular option that we can offer is to clean the existing paint off with the sand jet – gaining the advantages of low mess, contaminated paint control etc, then quickly re-blast the flash rusting with a dry grit blast – achieving the best of both worlds. 

 

High Pressure Water Jetting 

Another option is to use high pressure water (at around 500 to 1000bar) to remove all loose paint and rust from a surface.   Water at these pressures is very effective at removing rust (the sand jet or grit blast tends to have to wear it away – water seems to be able to get into the rust layers and lever the stuff off!) It also removes paint back to ‘well adhered’ primers, the advantages of this are that little flash rusting occurs – so a surface can remain unpainted for a few weeks without significant deterioration; the process is rapid – typically twice the speed of using abrasives. Also there is no abrasives to clean up or blow around a site (although the paint does tend to come off in ‘flakes’ which can cause a nuisance. The disadvantage is that not all the paint will be removed – and that the water jet doesn’t ‘scratch’ the surface, and some paint specifications will require a surface roughness so that the paint get an appropriate grip. 

Ultra High Pressure Water

Ultra High pressure water – to 2500bar will remove almost all paint from a surface – leaving it ready for repainting.   The advantages are the rapid removal of paint and preparation of a surface – the disadvantages are the high load on the operator (fighting against the lance!) and the relative length of the lance – which makes working underneath boats (for example) difficult.   Floors can be tackled with the same ‘scater’ tool we use for thermoplastic line removal – which imparts little load on the operator, and for large vertical surfaces, robotic attachments to cherry picker baskets can allow rapid surface cleaning with little operator fatigue.   Note again though that no surface roughness is imparted because water is the only ‘abrasive’; but a previously grit blasted surface should have the original surface profile restored. 

    Priming and Painting

    Primers and Topcoats can be applied to protect the steel from corrosion.  We now do favour moisture curing urethane products from Trident coatings for example, and topcoats from Firwood. The Moisture Curing Urethanes work down to -15 degrees C and at high humidities. This allows on site painting to take place, outside in Winter!

    A complex web of metal in an ex Aircraft Hangar in Warwickshire- cleaned and primed with MCU Aluprime Spring 2009.

    On Site Galvanising

    Zinga is a one-component cold applied galvanic zinc coating. Its unique formula provides environmentally safe cathodic protection to steel comparable with hot dip galvanising, with the added advantage that it can be applied, on site, like a paint. These columns were blast cleaned, and on site galvanised because they had been supplied in Zinc primer rather than galvanised finish. 

    Key Benefits

    • Zinga® means on site galvanising is possible. This therefore removes the dismantling and transport costs associated with hot dip galvanising.
    • Due to organic binder, Zinga can exceed lifespan of hot dip Zinc.
    • Zinga does not present any potential hydrogen inducement to load bearing welds therefore there is no danger of cracking. Steel coated with up to 60 um of Zinga does not require the grinding of edges before being welded to x-ray quality.
    • Zinga can be “recharged” at any point in the future, on site, and without re-blasting.
    • Worn or Rusty Galvanising can be also be repaired and re-charged
    • It can be used as a primer in a duplex system and can easily be painted over with a variety of top coats including powder coatings
    • Certified by the UK Ministry of Defence and US Military

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    Motor Vehicles

    One of the significant  advantages of the sand jet system is that thin metal surfaces don’t distort under blasting – which can happen with traditional blasting – because the damp nature of the blast cools the surface as it cleans. If flash rusting can be coped with (or light traditional gritblasting follows the sand jet removals) then this is an effective tool