Industrial and Infrastructure Coatings

Industrial coating is a corrosion and abrasion problem before it is an appearance problem. A coated pipeline, a composite moulding or a factory floor is expected to perform for decades in conditions that are actively hostile: moisture, chlorides, chemical spillage, ultraviolet, mechanical impact and thermal cycling. Colour and gloss matter, but they are the last thing the system delivers and the first thing that is given up when the layers underneath have been specified wrongly.

Specification starts with the exposure environment and the required service life, then works back to surface preparation, film build and system design. The Arcstruct range is written in the language of ISO 12944, which sorts atmospheric exposure into corrosivity categories from C1 to C5, adds the extreme category CX in the current revision, adds immersion and buried categories, and pairs each of them with a durability range. That framework settles how many coats are needed and how thick they have to be before any product is named. Surface preparation is described to ISO 8501-1, normally Sa 2.5 blast cleaning on new steel, with the anchor pattern graded to ISO 8503-2 and soluble salts sampled to ISO 8502-6 and measured to ISO 8502-9 before the first coat goes on. A system applied over a flattened profile or a contaminated surface fails at the interface, and no topcoat recovers that.

The three-coat logic behind the range gives each layer one job. The primer secures adhesion to prepared steel and provides either cathodic protection, through metallic zinc in electrical contact with the substrate, or barrier protection through inhibitive pigmentation and low permeability. Zinc-rich primers divide into two families and the difference is practical, not academic. Organic zinc, normally a two-pack epoxy binder, tolerates less than perfect preparation, recoats easily and suits fabrication shops and site work. Inorganic zinc, an ethyl silicate, cures by reaction with atmospheric moisture, gives a harder and more heat-tolerant film and longer protection at the same thickness, but it wants a clean blast, a controlled humidity window and a mist coat at overcoating because solvent escaping through the porous film will bubble a full wet coat. The intermediate coat buys film build and lengthens the diffusion path, usually a high-build epoxy pigmented with micaceous iron oxide or another lamellar pigment. The topcoat carries weathering, colour and gloss retention, because epoxy binders chalk under ultraviolet and will not hold appearance outdoors.

Flooring and composites sit in the same category because they are the same asset-life problem on a different substrate. On concrete, the choice between a thin roller-applied seal, a self-smoothing screed and a trowelled or broadcast system is a choice about mechanical duty and slip profile, and the usual cause of failure is not the resin but moisture in the slab, which drives osmotic blistering and disbondment under an impermeable film. On composites, a pigmented gel coat cast against the mould face is a different product from a coating applied to a cured laminate, and styrene content governs both workshop exposure control and the shrinkage and cure behaviour of the film. The boundary of this category is severe service. Immersion, marine and offshore exposure, tank linings and passive fire protection are specified from the Protective and Marine range, not from Arcstruct.

First coat onto prepared steel. Provides adhesion, and either cathodic protection from metallic zinc or barrier protection from inhibitive pigmentation, setting the corrosion performance of the whole system.

Two-pack epoxy intermediates that add film build, lengthen the moisture and ion diffusion path and carry abrasion duty. Includes surface-tolerant grades for maintenance work over aged coatings and hand-prepared steel.

Weathering layer. Holds colour and gloss under ultraviolet, resists chemical splash and cleaning, and sets the visual characteristics of the finished asset.

Line-applied coatings for steel pipe and tube. Internal grades reduce flow resistance and protect the bore, external grades carry buried or exposed corrosion protection and handling damage resistance.

Resin systems for concrete floors, plant rooms and bunded containment. Covers self-smoothing, broadcast and trowelled screed build, with primers matched to slab moisture condition and slip profile set by aggregate and seal coat.

In-mould gel coats and post-applied finishes for glass and carbon reinforced mouldings, addressing surface quality, weathering and styrene management in the workshop.

The figures below are the typical operating window for this range, not a measured result for any one batch. Confirmed values are issued with the Technical Data Sheet and Certificate of Analysis by our laboratory.

Preparation decides the result

The largest single cause of early failure in this category is preparation, not product. On steel, the specification names a cleanliness grade to ISO 8501-1 and a profile range to ISO 8503-2, and both are checked before the primer is opened. Soluble salt contamination on previously exposed steel is sampled to ISO 8502-6 and measured by conductivity to ISO 8502-9, then washed down, because chlorides left under the film draw moisture through it and lift the coating from the substrate. Welds, edges, bolt heads and back-to-back angles are stripe coated by brush before the main spray pass, since a sprayed film thins at every sharp edge and that is where corrosion starts. On concrete, the slab is shot blasted or diamond ground to open the surface, laitance is removed, and internal relative humidity is measured to ASTM F2170. A slab that reads high takes a moisture-tolerant primer or waits.

Building the system

Structural steelwork follows the three-coat pattern: Arcstruct PR primer, Arcstruct EP intermediate for build, Arcstruct PU topcoat for weathering. Coat-to-coat intervals matter in both directions. Below the minimum interval the underlying coat is still soft and solvent from the next coat will lift or wrinkle it. Above the maximum interval an epoxy surface has cured too far to bond chemically and needs abrasion before overcoating. Inorganic zinc is the exception that catches most crews. The porous silicate film holds air and solvent, so the intermediate coat is applied as a thin mist pass first and allowed to flash off before the full wet coat, otherwise the film pinholes and bubbles. An organic zinc epoxy does not behave this way and takes the intermediate coat directly. Cure of an inorganic zinc film is confirmed by solvent rub to ASTM D5402 before overcoating. Wet film thickness is checked with a comb during application and dry film thickness verified to ISO 2808 afterwards, because a system specified at a total build only performs at that build.

Line application on pipe and tube

Pipe coating is a controlled process rather than a site operation. The pipe is blast cleaned, heated, and coated on a moving line with the lance or spinning head set to deliver the specified thickness while the pipe rotates. Internal linings are applied thin and smooth because the benefit is hydraulic, and external coatings are applied heavy because the duty is mechanical and electrochemical. Every coated length is holiday detected to ASTM G62 or ASTM D5162 at a voltage matched to the film thickness, and the cutback at each end is masked so the girth weld and its field joint coating are not compromised. Coated pipe is not stacked or slung until the stated cure is reached.

Flooring, containment and composites

Floor systems are chosen by mechanical duty. A self-smoothing pour gives a seamless, cleanable surface for pedestrian and rubber-tyred traffic, and because it finds its own level it cannot form a fall. Where drainage falls are required they are cut into the slab or laid in a trowelled screed. A broadcast system, where aggregate is scattered into the wet resin and locked in with a seal coat, adds slip resistance and impact tolerance at moderate build. A trowelled screed at heavy build carries steel-wheeled traffic, thermal shock and point loading, and a polyurethane cement grade is used where hot washdown or steam would crack a filled epoxy. All three need anchor cuts at perimeters, drains and door thresholds, and coved upstands where the floor forms part of a bund. Slip performance is set by the aggregate grade and the seal coat, and is assessed by pendulum to BS 7976-2 or by ramp rating to DIN 51130. On composites, the decision is between a gel coat cast against the mould face, which gives the finest surface but ties the finish to the moulding cycle and brings styrene into the lay-up area, and an applied finish sprayed onto the cured part, which decouples colour from production, allows repair and fairing, and keeps styrene out of the finishing bay. Low styrene emission gel coat grades are available where the workshop is managing operator exposure and extraction load.

Conditions and cure

Two-pack systems are mixed complete, given the stated induction time and used inside the pot life, which shortens sharply as shop temperature rises. Substrate temperature is held at least 3 degrees above the dew point throughout application and initial cure, otherwise condensation forms in the film and amine blush or adhesion loss follows. Inorganic zinc needs humidity rather than dryness to cure, and polysiloxane cure is also moisture assisted, so a dry winter shop slows both. Full chemical resistance develops over several days and a floor put into chemical service too early will be marked permanently.

Arctic specifies from the exposure and the process, not from a product list. The following questions decide the answer, and a technical centre and laboratory in Greater Noida supports the work.

Exposure and service life

• Which ISO 12944 corrosivity category applies, from C1 to C5 or CX, and is the asset atmospheric, buried, splash zone or immersed? Immersion, marine and fire protection duty moves the enquiry to the Protective and Marine range.
• What durability range is required before first maintenance, and how accessible is the asset for repainting once it is in service?
• What is the operating temperature, continuous and peak, and is there thermal cycling or hot or cold insulated surface duty?
• Which chemicals, fuels or cleaning agents contact the surface, at what concentration, and as splash or standing spillage?
• Is there steam cleaning or hot washdown on the floor area, which decides between a filled epoxy and a polyurethane cement grade?
• Is the asset under cathodic protection, which makes adhesion retention under disbondment testing a governing property?

Substrate and preparation

• Carbon steel, galvanised steel, stainless, aluminium, concrete or composite, and new build or maintenance over an existing coating?
• What preparation is achievable on site or in the shop: abrasive blast to Sa 2.5, hand and power tool cleaning, or grinding only? This decides whether a surface-tolerant grade is required.
• Has the steel been in service, and will soluble salts be measured and washed down before the first coat?
• For existing coatings, what is the generic type, condition and adhesion, and has compatibility been checked with a test patch?
• For concrete, what is the slab age, internal relative humidity, presence of a damp proof membrane, the condition of existing joints and drains, and are drainage falls already formed in the slab?

Application and process

• Shop application, site application or a coating line, and what spray equipment is available: conventional, airless, plural component or heated?
• What are the ambient and substrate temperature and humidity ranges during application, and what is the shortest acceptable overcoating interval given the shop schedule? A dry shop slows inorganic zinc and polysiloxane cure, a damp one risks condensation in the film.
• What handling, stacking, transport and backfill loads does the coating see before it reaches full cure?
• Are there volatile organic compound limits, styrene exposure limits or extraction constraints at the site of application?

Performance, appearance and documentation

• What total dry film thickness and coat structure does the specification call for, and is there a maximum build constraint on moving parts or fits?
• What colour reference, gloss level and slip resistance class are required, and is colour matching to existing work needed?
• What inspection regime applies: holiday detection and at what voltage, adhesion pull-off, dry film thickness frequency and sign-off records?
• What batch size, packaging and shelf life suit the project, and is a compliance dossier or declaration required? These are issued on request.

The Technical Data Sheet, Safety Data Sheet and regulatory declaration for any grade in this range are issued by our laboratory against the substrate and process you are running. Tell us the job and we will specify against it.