Chemical protection rarely fails over the whole area at once. It fails at specific points: at a floor joint, next to a drain, at the edge of a sump, on a damp patch of concrete, at a single missed pore in the bottom of a vessel. That is why we handle the chemical protection of concrete and steel as an engineering task from start to finish: we establish what the coating will actually be exposed to, choose the class of system, work out the substrate and the details, prepare the specification and check the result on site. Supply of materials and application through partner contractors are added only if you need them.
We confirm chemical resistance only on the basis of a questionnaire. The choice of system depends on the specific substances and concentrations, temperature and thermal shock, mechanical loads and the washing regime, so it cannot be made from a general table. Fill in the questionnaire
Where chemical protection is needed
Chemical protection is needed wherever concrete or steel is in contact with acids, alkalis, salt solutions, oxidising agents, solvents or hot aggressive condensates — continuously, through spills or as vapour. Most often these are:
- chemical and petrochemical plants — acid and alkali storage areas and measuring tanks, reactor sections, neutralisers, pump rooms, loading and unloading areas;
- mineral fertiliser production — acid tanks and receivers, workshop floors and channels, structures in an atmosphere containing acid gases and fertiliser dust;
- mining and metallurgical plants — leaching and electrolysis areas, thickeners, slurry tanks and sumps, where chemicals are combined with abrasion;
- power generation — water preparation and chemical water treatment, reagent tanks, ducts and absorbers for flue gas cleaning;
- water treatment and sewage treatment plants — reagent tanks, channels, chambers and reservoirs; in sewerage structures, concrete is destroyed by hydrogen sulphide and the sulphuric acid formed from it;
- food production — floors, drains and channels in workshops with organic acids, fats, hot washing and disinfection.
Where we start: the medium, the facility and the questionnaire
Selection starts with the question of “what the coating will be exposed to”, and the answer is almost always broader than “acid”. We collect the data with a questionnaire and, on an operating facility, verify them on site.
- Medium: all substances, their concentrations and mixtures, impurities and solvents, oxidising agents, solid particles; products that replace one another in the same vessel, and the solutions used to wash it out.
- Temperature: operating and peak, thermal shocks — steaming out, hot washing, hot product discharged onto a cold floor.
- Contact regime: permanent immersion, fluctuating level, splashes and spills, vapours and condensate above the liquid.
- Mechanical action: abrasion by slurry, impacts, the wheels of forklifts and trolleys, equipment vibration.
- Substrate: steel or concrete, new or already damaged by the medium, soaked with acid or oil, with cracks and an old coating.
- Working conditions: for how many days the area can be shut down, temperature and humidity in the workshop, ventilation of confined spaces, work next to operating equipment.
On an operating facility, we also look at how and where the existing protection is breaking down: the depth of damage to the concrete, the condition of the reinforcement and cast-in items, pitting on the steel, residues of salts and product. The cause of the previous failure is the main argument when choosing a new system. How such a survey is carried out is described on the “Coating surveys and failure analysis” page.
Classes of systems we choose from
Each class of material has its own field of application and its own limitations, while the grade and thickness are determined by the resistance confirmed by the manufacturer for your medium and temperature.
| System class | Where we usually use it | What to bear in mind |
|---|---|---|
| Epoxy novolac coatings and linings | vessels, drip trays and floors with acids and alkalis within the confirmed resistance, solvents, fuels, elevated temperatures | dense cross-linking widens resistance compared with ordinary epoxies, but epoxy systems are, as a rule, vulnerable to strong oxidising agents |
| Vinyl ester coatings and linings, bisphenol and novolac | acids, including oxidising acids, salt solutions, hypochlorite, ducts and absorbers | short pot life, strict requirements for substrate temperature and dryness, limited overcoating interval |
| Glass-flake systems | immersion, strong vapour diffusion, hot acidic media; thick coats in one to three passes | the barrier works only if the flakes are correctly aligned in the film, so the application method and the applicator’s qualifications matter |
| Reinforced laminates on glass mat or glass cloth | concrete vessels, sumps, drip trays, channels and floors with aggressive spills; crack bridging | a multi-layer hand-applied technique that is demanding in terms of wetting out the reinforcement and removing air |
| Linings: rubber linings, sheet thermoplastics, acid-resistant tiles and bricks laid in chemical-resistant mortars | chemicals combined with abrasion, hot concentrated media, floors under impact and thermal loads | their own techniques and timescales — vulcanisation, sheet welding, masonry — and their own requirements for the structure to be lined |
| Polyurethane cement floors | workshops with hot washing and thermal shocks, food and chemical production | the permissible temperature and resistance depend on the grade and layer thickness — we take them from the manufacturer’s documents |
The classes are not interchangeable. A vinyl ester on damp concrete, an epoxy exposed to an oxidising agent or a thin polymer floor exposed to hot washing fails even if applied flawlessly. Materials of these classes are collected in the “Chemical protection” section of the catalogue.
Concrete: strength, cleanliness, moisture
Most chemical protection failures on concrete are failures of the substrate, not of the coating. That is why we specify the requirements for the concrete in as much detail as those for the system itself:
- A sound surface layer. Laitance, a weak top layer and concrete damaged by the medium are removed down to a sound substrate by shot blasting, scarifying, grinding or water jetting. We check the strength of the substrate and the bond to it on a trial area by the pull-off method — to ASTM D7234 or ISO 4624 — and record the results in a report.
- Contamination. Oil, product and salts that have soaked into the concrete cannot be washed off the surface. Such concrete is cleaned using the system manufacturer’s procedure or removed, otherwise the coating will delaminate from within.
- Moisture. A damp substrate and moisture pressure from below are a common cause of blistering and delamination. We measure moisture before application, for example by the plastic sheet method to ASTM D4263 or with probes in drilled holes to ASTM F2170, and compare it with the limit given in the manufacturer’s documents. If the concrete cannot dry out in time or moisture is pushing up into a ground-bearing slab, we specify a primer that tolerates a damp substrate or a vapour barrier layer from the same system.
- Repairs and falls. Honeycombing, spalls and deteriorated areas are made good with repair compounds compatible with the coating. Falls to drains are formed before the chemical protection, so that the medium does not stand on the floor.
- Cracks. Static cracks are repaired and bridged; moving cracks are either converted into a movement joint or bridged with a reinforced system designed for that amount of opening.
Steel: preparation and design
- abrasive blast cleaning, usually to Sa 2½ or Sa 3 to ISO 8501-1, with the surface profile required by the system (ISO 8503);
- checking dust to ISO 8502-3 and water-soluble salts to ISO 8502-6 and ISO 8502-9: salts under a lining in immersion service are a common cause of blistering;
- preparation of welds, edges and surface imperfections to ISO 8501-3 — for immersion, usually to the most stringent grade, P3: continuous welds ground smooth, rounded edges, no spatter or undercut;
- small design details that decide the outcome: crevices inaccessible for painting, internal stiffeners, bolted connections inside the vessel. These are best eliminated at the vessel design stage — following the principles of ISO 12944-3.
Details where chemical protection fails
The general area is the easiest part of the job. Failures begin at the details, so for each of them we provide a solution and a sketch:
- movement and construction joints — a chemical-resistant sealant or profile, taking the coating down into the joint, reinforcing the edges;
- drains, trenches and sumps — continuity of the coating up to the drain body, junctions with stainless steel components, edge protection;
- pipe and anchor penetrations — taking the coating up onto the pipe, sealing the gaps, reinforcement around the penetration;
- upstands and junctions with walls and columns — a cove instead of a right angle, the height to which the coating is taken up the vertical, terminating the coating in a key groove rather than feathering it out “to nothing”;
- pump and equipment foundations — protection of the plinth, chemical-resistant grout under the base frame, a solution around the anchor bolts;
- transitions between systems and substrates — concrete and steel, new and old areas, floor and bund: we determine which layer goes over which and how to join them;
- nozzles, manholes and internal parts of vessels — preparation, application sequence and continuity testing where access is most difficult.
Epoxy grouts for equipment, including those for areas with aggressive spills, are covered in the “Epoxy grouts” section.
What the chemical protection specification includes
- a map of the facility’s zones by medium, temperature and load, with a protection system for each zone;
- the make-up of each system: primer, coats, reinforcement, topcoat, nominal and minimum thickness;
- substrate requirements: strength, cleanliness, moisture, profile, repairs and falls;
- application conditions: substrate and air temperature, dew point, humidity, ventilation, protection from sun and dust;
- overcoating intervals and the curing time before entry into service, taking the temperature into account;
- detail solutions with sketches;
- an inspection plan with points at which work stops until accepted, and with measurable acceptance criteria;
- two or three equivalent material options from different manufacturers and a schedule of materials for your quantities.
How we prepare such documents is described on the “Painting specifications and documentation” page.
Quality control
| Stage | What we check | Methods and standards |
|---|---|---|
| Before application | climatic conditions and dew point; cleanliness and profile of the steel; dust and salts; pull-off strength of the concrete on a trial area and its moisture content | ISO 8502-4; ISO 8501-1, ISO 8503; ISO 8502-3, ISO 8502-6, ISO 8502-9; ASTM D7234 or ISO 4624; ASTM D4263, ASTM F2170 |
| During the work | wet film thickness, number of coats and intervals, wetting-out of the reinforcement, absence of air in the laminate | ISO 2808 and the rules of the inspection plan |
| After application | dry film thickness; continuity; adhesion; cure | on steel — ISO 19840; on concrete — ultrasonically to ASTM D6132 or on test panels; continuity — ISO 29601, on steel ASTM D5162, on concrete ASTM D4787; adhesion — by pull-off on test areas; cure — by the method specified by the manufacturer, for example hardness or a solvent rub test to ASTM D5402 |
For vessel linings and coatings in immersion service, spark testing for continuity is a mandatory hold point: the vessel is not filled until all holidays have been found, repaired and retested. The voltage is set by the manufacturer according to the coating type and thickness. On concrete, we agree the method in advance: sometimes a conductive underlayer is built into the system to allow reliable spark testing. More on the methods is given on the “Testing and quality control” page.
Supply, application and supervision
We do not carry out the work ourselves. We are responsible for the solution and for making sure it is implemented without substitutions:
- we supply the materials of the selected system as a complete set, with the manufacturer’s documents for each batch — see “Supply of materials and organisation of application”;
- we select a partner contractor with experience specifically in chemical-resistant systems: laminates, vinyl esters, rubber lining, polymer floors;
- before work starts, we go through the specification and the details with the applicators, start with a trial area and accept it as the reference standard;
- we inspect the work at the points of the inspection plan or hand inspection over to an independent inspector — see “Technical supervision of coatings”;
- we hand over a quality dossier: reports, certificates, recommendations for inspections and repairs.
In Uzbekistan, the execution and acceptance of corrosion protection work are governed by Construction Regulation QR 04.01-23: the work log, records for intermediate stages, and checks of continuity, bond to the substrate and thickness on acceptance. The requirements for designing the protection of structures against corrosion are set by ShNK 2.03.11-24: the degrees of aggressive environmental exposure for concrete and metal and, for concrete, also exposure classes, including chemical and biological attack (XA1–XA3). For more details, see the “Corrosion protection standards” section.
Input data
- a completed questionnaire or a description of the media, temperatures and operating regime;
- drawings or plans of the areas, vessels, floors and channels; photographs if the facility is in operation;
- the type and condition of the substrate, information on previous coatings and their failures;
- timescales and permissible downtime, working conditions;
- project and client requirements: codes, hygiene and fire safety requirements, documentation requirements.
If chemical protection is already included in the design, you can send the section to us for a free express review — details are on the “For designers” page.
What you receive
- a conclusion on the medium and the service conditions of the coating by zone;
- a chemical protection scheme for each zone, with thicknesses and substrate requirements;
- a specification, detail solutions and an inspection plan;
- a comparison of two or three material options and a schedule of materials;
- if you wish — supply, application by partners and inspection through to acceptance.
We work throughout Uzbekistan and, on request, in neighbouring Central Asian countries. See also: tank and vessel protection, development of protection schemes, all engineering services.
Describe the medium and the area, and we will suggest where to start: with a survey, with a scheme or straight away with a specification. Phone, WhatsApp, Telegram: +998 94 094 52 27. Questionnaire, drawings and photographs: info@ognezashita.uz.