Pickling and Passivation Services for Industrial Systems
Chemical cleaning removes contaminants such as mill scale, rust, weld oxides, grease, and construction debris from the internal surfaces of piping, vessels, and boilers using engineered chemical solutions. It is a critical pre-commissioning step that protects new systems from corrosion and prevents debris from damaging valves and rotating machinery at start-up.
As a provider of chemical cleaning services in the UAE, Tensor delivers degreasing, acid pickling, passivation, and neutralization for oil and gas, marine, and industrial clients. This guide explains the process, where it is used, and what to confirm before handover.
What Is Chemical Cleaning, Pickling, and Passivation?
Chemical cleaning uses circulating or soaking chemical solutions to strip organic and inorganic contamination from metal surfaces. Pickling then removes a thin layer of metal, including mill scale, rust, and weld discoloration, using acid solutions. Passivation finally treats the cleaned surface (particularly stainless steel) so it forms a uniform, protective chromium-oxide layer that resists corrosion. Together they leave piping and equipment clean, stable, and ready for service.
Why Is Chemical Cleaning Needed Before Commissioning?
During construction, internal surfaces accumulate scale, rust, welding residue, grease, protective coatings, and debris. If these are not removed before start-up, they can accelerate corrosion, foul heat-transfer surfaces, reduce flow, and damage valves and machinery. Chemical cleaning eliminates these hazards, extends asset life, and protects product purity, which is why it is best practice on new-build piping and equipment before client handover.
What Are the Stages of the Chemical Cleaning Process?
A typical pickling and passivation sequence for steel follows these stages:
| Stage | Purpose |
|---|---|
| Degreasing | Remove oils, grease, and protective coatings. |
| Water rinse | Flush away loosened contaminants. |
| Acid pickling | Remove mill scale, rust, and weld oxides. |
| Neutralization | Neutralise residual acid to a safe pH. |
| Passivation | Form a protective chromium-oxide layer. |
| Drying | Remove moisture to prevent flash corrosion. |
For hydraulic and lube-oil lines, specialist equipment forms temporary circuits so chemicals can circulate through complex assemblies. Where systems are best cleaned by circulating oil rather than acids, oil flushing is used instead. See our guide to oil flushing.
Where Is Chemical Cleaning Used?
- Boilers, HRSG systems, and steam lines.
- Process piping, spools, and pipelines.
- Heat exchangers, coolers, and condensers.
- Vessels, tanks, and cooling-water systems.
- Stainless steel tanks and process equipment requiring passivation.
How Is the Right Chemistry Selected?
Product selection depends on the metal type and whether heat can be applied. Carbon steel is often treated with organic-acid products (sometimes with heat) that remove rust while being gentle on the metal; higher-grade steels tolerate mineral acids and can be treated at ambient temperature for faster cleaning. After pickling, an alkaline-based passivation product restores surface pH and prevents flash corrosion, something flushing alone cannot reliably achieve.
Which Standards Apply to Passivation?
Passivation of stainless steel is commonly carried out and verified to ASTM A967 / A380. Confirm the cleaning and passivation procedure, the acceptance criteria, and the test method (for example surface testing for free iron) as part of the documentation package.
Chemical Cleaning Services in the UAE
Tensor provides chemical cleaning, pickling, and passivation, on-site or at our yard, across the UAE, with ISO-compliant procedures and experienced technicians. As part of a full pre-commissioning package, we combine chemical cleaning with flushing, drying, and testing through a single provider.
Request a quote for chemical cleaning, or explore our full Pre-Commissioning Services.
FAQs
Pickling uses acid to remove a thin contaminated layer from the metal, including mill scale, rust, and weld oxides. Passivation then treats the cleaned surface so it forms a uniform protective oxide layer that resists corrosion. Pickling cleans; passivation protects.
New piping and equipment hold scale, rust, welding residue, grease, and debris that can cause corrosion, foul heat-transfer surfaces, and damage valves and machinery at start-up. Chemical cleaning removes these contaminants so the system is safe to commission.
No. Chemical cleaning uses acids and other chemistry to treat metal surfaces, while flushing circulates oil or fluid to remove particulate to a target cleanliness class. They are different methods used for different systems and are often complementary.
Carbon steel, stainless steel, and alloy steels can all be treated, with the chemistry and temperature selected to suit the metal. Stainless steel in particular benefits from passivation to restore its protective chromium-oxide layer.
Passivation of stainless steel is commonly performed and verified to ASTM A967 / A380, which define the treatment and the acceptance testing such as checking for free iron on the surface.
Tensor provides chemical cleaning, pickling, and passivation across the UAE, on-site or at our yard, as part of a complete pre-commissioning package that also covers flushing, drying, and testing.
