Pressure vessel protection

When the existing protective coatings on a pressure vessel in Yorkshire, UK had reached the end of their service life, resulting in visible pitting, laminate corrosion and reduced long-term corrosion protection, Corroless Eastern was brought in to solve the problem.

Because the pressure vessel is in an area with active chemical processes, the steelwork had become contaminated with chemical salts, increasing environmental corrosivity and accelerating deterioration.

To maintain safe operation and prevent further structural degradation, the client required a complete replacement industrial protective coating system engineered for harsh, high-corrosivity environments.

The solution

Given the aggressive on-site conditions, Corroless Eastern specified a high-build, solvent-free polyurethane protective coating system applied to a nominal thickness of 1,000 microns.
In accordance with ISO 12944, this coating specification provides very high durability (25+ years), even in a C5 corrosivity environment, making it ideal for long-term corrosion protection of industrial pressure vessels.

Contamination removal

The pressure vessel’s surface was heavily contaminated with salts and chemical residue, so the first step was thorough high-pressure washing to remove contaminants, debris and badly-adhered remnants of previous coatings. As the original coatings had been applied poorly, large areas detached during the cleaning process.

To control environmental conditions before blast cleaning, dehumidifiers were installed to reduce humidity and prevent flash rusting on exposed steel.

Grit blasting of the pressure vessel

All remaining coatings were removed from the pressure vessel, and the steel substrate was prepared to SA 2.5 in line with ISO 8501-1, ensuring an optimal surface profile for long-life industrial coating systems.

A surface profile needle gauge was used to verify the required anchor profile. Following removal of existing coatings, soluble salt testing was carried out to ensure the surface was free from contaminants that could compromise the new coating system.

If salts had been detected, the steel would have required further washing and re-blasting  ̶  a critical step in preventing osmotic blistering and premature failure of high-performance protective coatings.

Climate condition monitoring

Throughout all stages of surface preparation and coating application, climatic conditions (temperature, humidity, dew point) were continuously monitored and recorded to ensure compliance with manufacturer requirements and coating performance standards.

Coating application

A solvent-free, high-build polyurethane coating was applied in two full coats to achieve the specified 1000-micron dry film thickness. A separate stripe coat was used on welds, edges and sharp geometries where coatings typically draw thin due to surface tension.

Dry film thickness readings were taken and documented throughout the process to ensure full coating integrity and compliance with specification.

Topcoat finish

To complete the coating system on the pressure vessel, an aliphatic polyurethane topcoat was applied in the required colour to match the client’s pipework colour scheme. This topcoat provides enhanced UV stability and a high-quality, durable finish suitable for demanding industrial environments.

Long-term corrosion protection

The pressure vessel now benefits from a robust, fully compliant industrial protective coating system engineered for long-term performance in a C5 corrosivity environment. Through correct surface preparation, salt testing, climate control and the use of a high-build polyurethane system, Corroless Eastern has restored the asset to a high-durability condition with an extended service life.

More articles like this can be found in the latest issue of Protective Coatings Expert