Surface Preparation

Surface preparation is the essential treatment of the substrate or surface that is required to allow other works to be carried out. Certain standards of cleanliness or preparation are required depending on what it is being prepared for, for example NDT inspection, mechanical repairs, lining or coating application etc. The purpose of the surface preparation works usually dictates the standard of cleanliness required, which in turn determines the method of surface preparation.

Over 90% of premature protective coating or tank lining failures are a result of improper or inadequate surface preparation. Ensuring proper surface preparation to the correct standards of cleanliness is critical to ensuring the longevity and intended performance of any protective coating or tank lining. Before applying any protective coating or tank lining, the surface or substrate must be suitably cleaned to remove any grease, dirt, grime, algae/growths, soluble salts, failed existing coatings, rust etc. down to within acceptable parameters. Having a competent surface preparation contractor such as Ferrous Protection Ltd who understands these parameters and how to properly test for them is paramount to achieving a successful surface preparation and protective coating project.

There is a wide range of surface preparation techniques on the market, each with its advantages and disadvantages. Having a competent surface preparation partner such as Ferrous Protection is critical in ensuring the most appropriate surface preparation technique is chosen to ensure the project is delivered safely, sustainably and to the required standards.

. Such methods of surface preparation include:

• Abrasive Blast-Cleaning (Shot Blasting, Grit Blasting): Using pressurised air to propel abrasive material against a substrate to remove contaminants and create a textured surface.
• Wet Abrasive Blast-Cleaning (Wet Blasting): Using pressurised air to propel abrasive material against a substrate to remove contaminants and create a textured surface, including a water stream at the nozzle to suppress dust.
• Power Tool Cleaning: Using rotary wire brushes, bristle blasters, grinding disks etc. to clean the localised areas of corrosion or coating failure.
• Water Jetting: Utilising a range of low, high and ultra-high pressure water jets to achieve varying levels of surface cleanliness from removal of contaminants through to complete removal of an existing coating back to bare steel.
• Chemical Cleaning: Applying specialised chemicals to dissolve or remove contaminants like oil and grease.
• Robotic Crawlers: Magnetic remotely controlled units with vacuum recovery heads that can grit blast and water jet surfaces without the need for personnel to work at heights.
• Electro-magnetic Thermal Induction: This specialised approach reduces the adhesion of existing coatings for easier removal.

Ferrous Protection recently abrasive blast-cleaned from fixed scaffold the internal of a bulk liquid storage tank at a major UK airport. To avoid introducing trace copper into the tank which can present safety hazardous in Jet-A1 tanks, garnet (an inert, naturally occurring semi-expendable mineral abrasive) was used. The experienced and competent grit blasting operatives blasted off the existing lining from the floor, shell, roof and roof structure to ISO8501-1 Sa2½ standard of cleanliness and the garnet impacted the steel at high speed to create an angular surface profile of 50-75 microns. This provided the tank internal with optimum surface preparation conditions for re-application of a highly effective chemical and corrosion resistant tank lining. This level of surface preparation gives the tank lining the best possible chance of protecting both the asset and jet fuel for many years to come and provide the asset owner with complete peace of mind.

The most suitable method of industrial surface preparation is typically decided by the level of surface cleanliness required. This is usually determined by the type of coating to be applied and the nature of the site/asset to be treated. For example, there are various surface tolerant coatings available on the market that are designed to offer optimal adhesion over lower standards of cleanliness such as substrates prepared by water jetting or power-tool cleaning. Other coatings such as metal spray, zinc based coatings require higher levels of surface preparation such as ISO8501-1 Sa3 which can only be achieved by abrasive blast-cleaning.

The site and asset can also affect the type of surface preparation used on a project, for example if the existing coating is lead based or over a water course, abrasive blast-cleaning is often considered not the most suitable means of surface preparation due to the risk of environmental pollution, in which case using systems with vacuum recovery hoods or mechanical cleaning may be considered.

If the existing coating is largely intact and sound with only localised areas of corrosion or mechanical breakdown, they asset owner may decide to perform localised “touch ups” rather than fully removing and re-coating, in which case low pressure water jetting and mechanical cleaning can be utilised to remove contaminants and bring any corroded areas back to bare steel reading for patch coating repairs.

Surface preparation typically involves the use of electric or pneumatic equipment operating at high voltage or pressures. They can also involve hazardous materials and processes and require to be carried out in high risk areas such as at height or in confined spaces. Ensuring surface preparation works are performed safely and to the relevant health and safety standards is critical in achieving project success. Ferrous Protection prioritises safety by:

• Utilising advanced technology and techniques to carry out surface preparation works.
• Using only highly competent, trained and experienced surface preparation prfoessionals to perform works.
• Undertake high level surface preparation training at our premises by qualified and time served trainers.
• Lead abatement provisions in line with CLAW regulations for removing lead based coatings such as medical surveillance (lead in blood tests), lead in air monitoring, decontamination facilities etc.
• Having robust safety procedures and systems including robust sets of task- and site-specific RAMS for each project.
• Utilising appropriate personal protective equipment (PPE) and respiratory protective equipment (RPE) for workers.
• Where required, implementing forced ventilation and forced extraction through utilising engineering controls to maintain high levels of visibility.

Oftentimes, surface preparation requires the use of hazardous materials and also the removal of hazardous materials. These can include oil contaminated washings from pressure washing, to lead dust from blasting lead contaminated paint. Each project will present its own environmental hazards which will be thoroughly risk assessed by Ferrous Protection Ltd’s HS&E team to ensure suitable and sufficient control measures are in place. We work with a properly vetted and reputable supply chain for our waste management services and can carry out various waste characterisation tests to ensure the correct disposal routes and waste streams are used. Where possible, all environmental and pollution hazards will be minimised by taking the sustainable alternative, for example using inert and naturally occurring abrasives or captive blasting over expendable abrasives. Scaffold and shrink wrap encapsulated habitats can also be utilised to create our own work area to ensure no hazardous materials escape to the local atmosphere. Other projects allow for vacuum recovery systems which remove the spent grit / washings immediately from the workface.

Yes. Ferrous Protection employ several ICorr Protective Coating Inspectors who are specially trained in all methods of surface preparation and protective coating techniques. If you are not sure on the most appropriate surface preparation technique for your project, don’t hesitate to get in touch for some advice or to arrange a site survey to discuss your requirement in more detail.