A tank is not a single surface but several zones that corrode in different ways: the bottom with bottom water and sediment, the shell immersed in the product, the vapour space under the roof, the external surfaces exposed to the atmosphere, the underside of the bottom resting on the base and, sometimes, steel under thermal insulation. Each zone needs its own protection system, and a mistake in any one of them shortens the service life of the whole tank. We develop zone-by-zone protection for tanks and vessels — for new and operating facilities: from choosing a lining for the product to acceptance of the work and a repair plan.
For chemical products, we confirm the resistance of a lining only on the basis of a questionnaire: substance, concentration, temperature, filling and cleaning regime. Fill in the questionnaire
Which tanks and vessels we design protection for
- vertical and horizontal steel tanks, above-ground and underground;
- reinforced concrete tanks and liquid-retaining structures for water, wastewater and reagents;
- process vessels, measuring tanks, receivers, settling tanks, reagent tanks.
By product:
- water — drinking water, process water, firefighting reserve, hot water;
- oil and petroleum products — crude oil, petrol, diesel fuel, fuel oil, aviation fuel, biofuels;
- chemical products — acids, alkalis, salt solutions, hypochlorite, solvents, liquid fertilisers.
Tank zones and what we decide for each
| Zone | What acts on it | What we decide |
|---|---|---|
| Interior of the bottom and the bottom shell course | bottom water with salts, sediment, microbiological corrosion, wear during tank cleaning | bottom lining carried up onto the shell, thickness and reinforcement according to the condition of the steel, repair of pitting before application |
| Shell in the product zone | immersion, product temperature, change of products, product purity requirements | full or partial lining — depending on the product, its purity requirements and the corrosion history |
| Vapour space and roof interior | condensate, oxygen, product vapours, temperature fluctuations | a system for the condensation zone, preparation of the roof framework, solutions for the pontoon and the floating roof |
| External shell and roof | atmosphere, sun and UV, dust, temperature fluctuations; on the roof — ponding water | an atmospheric system according to the corrosivity category and the required durability |
| Annular plate and the “shell — bottom — foundation” joint | rainwater running in under the annular plate, dirt, salts | protection of the annular plate, sealing of the gap with an elastic system, drainage of water |
| Underside of the bottom | moisture and salts from the base; after erection the surface is inaccessible | decisions before assembly: the tank base, coating of the plates and cathodic protection — if the design provides for them |
| Steel under thermal insulation | moisture under the insulation at elevated or cyclic temperatures | a system for service under insulation, insulation and cladding details |
| Supports of vessels containing flammable media | a possible hydrocarbon fire | fire protection of the supports, if required by the design, compatible with the corrosion protection system |
Internal coatings by product
Water and drinking water
For process water, what matters is resistance to permanent immersion, to abrasion and to the water temperature. For drinking water, hygiene documents for the material that are recognised in Uzbekistan are needed as well: foreign approvals, for example to NSF/ANSI/CAN 61, confirm the properties of the material but do not replace those documents on their own. We check that the documents are available before the material is chosen, and we set the curing, flushing and the procedure for putting the tank into service according to the manufacturer’s requirements. For reinforced concrete tanks, we solve two problems at once: keeping the water in — joints, penetrations, junctions — and protecting the concrete if the water is aggressive to it. The materials for this are in the “Waterproofing” section.
Oil and petroleum products
The lining is chosen according to the product and the temperature: epoxy systems for water, crude oil and many petroleum products; novolac and epoxy phenolic systems for a wider range of products and solvents and for elevated temperatures; solvent-free systems for a thick coat in a single pass and reliable coverage of pits and edges. For tanks holding flammable products, the design may require a conductive coating. For aviation fuel, the coating must have the proof of suitability that the client requires — we clarify these requirements before the material is chosen. For linings of the bottoms and internal surfaces of above-ground tanks, international specifications refer to API RP 652; its sixth edition was published in December 2025.
Chemical products
For acids, alkalis and oxidising agents, we choose from vinyl ester and novolac linings, glass-flake systems, rubber linings and sheet thermoplastics — only on the basis of a questionnaire. We deal separately with what destroys a lining more often than the chemicals themselves: steaming out and hot washing, vacuum during emptying, changes of product, abrasive sediment. The approach is described in detail on the “Chemical protection of concrete and steel” page.
External corrosion protection by corrosivity category
External surfaces are protected with atmospheric systems. We determine the corrosivity category to ISO 12944-2 for the specific site, not for the region: the dry climate of most of Uzbekistan does not guarantee a mild environment if there are industrial emissions, saline dust or constant product spills nearby. For underground tanks the standard defines a separate category, Im3 — soil, and for structures in fresh water, Im1. In the national codes, the same task is addressed by ShNK 2.03.11-24: through the degree of aggressive environmental exposure and the coating group and thickness.
- we agree the required durability with the client using the ISO 12944-1 ranges — from L to VH — and select the system to ISO 12944-5;
- for heated tanks, we select systems designed for the shell temperature;
- we choose a UV-resistant topcoat and agree the colour with the process engineer: it determines how much the product heats up in the sun;
- we take into account where the painting will be done — at the factory, during erection or on the finished tank — and in which season: heat, dust and wind change the procedure.
More on environment categories and systems is in the “Corrosion protection” section, and a preliminary assessment is available in the online corrosion protection system selector.
Bottom, annular plate and roof
- Bottom interior. Bottom water, salts and sediment collect here, so the bottom and the bottom shell course are protected first. Before lining, we assess the pitting and the remaining plate thickness together with the tank inspector: deep pits and thinned areas are repaired by welding or patch plates before application, while shallow ones are filled with compounds from the lining system. On worn bottoms, we consider reinforced systems.
- Annular plate and the junction with the foundation. Water running in between the annular plate and the foundation eats away at the bottom from below around the perimeter, unnoticed, for years. The joint is cleaned, the annular plate is protected and the gap is closed with an elastic system that withstands shell movement during filling and emptying — with water drained away from the tank.
- Underside of the bottom. Once the tank has been erected, it can no longer be repainted, so protection is built in before assembly: decisions on the tank base, as well as coating of the underside of the plates and cathodic protection, if the design provides for them. In international practice, API RP 651 is used for cathodic protection of tank bottoms; in that case the coating must be compatible with cathodic protection.
- Roof exterior. Ponding water, dirt, sun and temperature fluctuations: the system must withstand constant wetting and UV, and ponding areas must be eliminated or reinforced.
- Roof interior and vapour space. Condensate, oxygen and product vapours, difficult access and poor ventilation during painting. The decisive factors here are the preparation of the beams and joints of the roof framework, stripe coating and the application conditions inside the tank.
Corrosion under insulation and fire protection of supports
On heated tanks — fuel oil, bitumen, viscous products — steel under thermal insulation corrodes out of sight. For such surfaces, we select systems tested for service under insulation at operating and cyclic temperatures: international specifications qualify them to ISO 19277, and measures against corrosion under insulation are described in API RP 583. For more details, see the “Heat-resistant coatings” section.
If a vessel or apparatus containing a flammable liquid or gas stands on steel supports — legs, a skirt, saddle supports — the design may require fire protection of these structures against a hydrocarbon fire. We coordinate such fire protection with the corrosion protection system — primer, fire protection layer, topcoat, protection against corrosion under the fire protection — and calculate the thickness for the section and the required fire resistance rating. See “Hydrocarbon fire protection” and “Calculations and justification”.
Survey and repair of operating tanks
Repairing a tank coating means a shutdown, cleaning, gas-freeing and work in a confined space, so the solution has to be right first time. On an operating facility, we:
- study the history: product, temperatures, previous coatings, results of earlier inspections;
- assess the coating during a scheduled shutdown — rusting, blistering, cracking and flaking to ISO 4628, thickness, adhesion, continuity, condition of welds and details;
- coordinate the coating repair with the repair of the steel: the tank itself — shell and bottom thicknesses, welds, base — is inspected by a tank inspector, in international practice to API 653;
- choose the strategy: local repair, replacement of the coating on the bottom and the bottom shell course, or complete relining — taking into account the permissible downtime and the remaining service life;
- specify the working conditions inside: ventilation, dehumidification and heating of the air where necessary, lighting and access, so that the material cures properly.
How a survey and the search for the causes of failure are carried out is described on the “Coating surveys and failure analysis” page.
Codes and standards we apply
The references depend on the codes to which the project is designed and on what the client requires:
- Uzbekistan: ShNK 2.03.11-24 — design of corrosion protection of structures; Construction Regulation QR 04.01-23 — execution and acceptance of work, including coatings on process equipment;
- ISO: the ISO 12944 series — environment categories, durability, coating systems and their laboratory assessment; ISO 8501–8503 — surface preparation; ISO 19840 and ISO 29601 — coating thickness and continuity;
- API: API RP 652 — tank linings, API RP 651 — cathodic protection of tank bottoms, API 653 — tank inspection and repair, API RP 583 and ISO 19277 — corrosion under insulation;
- NORSOK M-501 — on facilities where the client works to it; since the 2022 edition, it has included pre-qualification of tank linings.
An overview of the documents is given in the “Corrosion protection standards” section and on the “Corrosion protection in oil and gas and offshore” page.
How we work
- Enquiry. The type and dimensions of the tank, the product and temperature, whether it is new or in operation, what the design and the client require.
- Survey. For operating tanks — during a shutdown, or beforehand on the basis of documents and photographs.
- Zone-by-zone scheme. A protection system for each zone, two or three equivalent material options from different manufacturers, calculation of quantities.
- Documents. Specification, detail solutions, inspection plan with hold points, coating repair procedure.
- Execution. If you wish — supply of materials, application by partner contractors, inspection and acceptance with a quality dossier. We do not carry out the work ourselves, but we are responsible for making sure the scheme is implemented without substitutions.
Input data
- drawings or the tank data sheet: type, dimensions, material, whether there is a pontoon, heating, thermal insulation;
- the product or products, temperature, filling and cleaning regime, presence of bottom water;
- location: open site, neighbouring plants, soil and base;
- project and client requirements: codes, durability, colour, hygiene and fire safety requirements;
- for operating tanks — the coating history, reports of previous inspections, photographs, permissible downtime.
What you receive
- a zone-by-zone protection scheme with thicknesses and surface preparation requirements;
- a comparison of material options and a schedule of materials;
- a specification, detail solutions and an inspection plan;
- for operating tanks — a coating survey report and a programme for its repair;
- recommendations for inspection and maintenance of the coating between repairs.
We work throughout Uzbekistan and, on request, in neighbouring Central Asian countries. Materials for internal protection are in the “Coatings for tanks and pipelines” section of the catalogue, and all services are in the “Engineering” section.
Send us the tank and product data, and we will propose a zone-by-zone protection scheme or a survey programme. Phone, WhatsApp, Telegram: +998 94 094 52 27. Drawings, reports and photographs: info@ognezashita.uz.