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Preventing Stress Corrosion Pitting

OVERVIEW:    The 304 stainless steel ammonia absorber and circulation tank experience temperatures of up to 100°C and an aggressive Chemical environment. 

The prevention of stress corrosion pitting was achieved in the heat affected areas by applying corrosion protection on the entire internal surface.

ENVIRONMENT

Normal operating temperature is 60-70°C. Excursions up to 100°C are common.

• Wet ammonia gas

• Diluted sulphuric acid (up to about 20%)

• Ammonium sulphate

• Naphthalene

• Benzene

• Aromatic and aliphatic hydrocarbons

• Hydrogen sulphide

• Hydrogen cyanide

SUBSTRATE

304 Stainless Steel – Ammonia absorber and circulation tank

CHALLENGE

Prevent Stress Corrosion Pitting in the heat effected areas, these are generally found either side at the toe of the weld. Apply corrosion protection on the entire internal surfaces within a 72 hours outage

SOLUTION

Abrasive blast to Chemcote’s Specifications and 3 coats of Chem-tect™ RF 300 Series

SCOPE

Recommend the entire internal surfaces are treated

Mobilise on site

Set up of dust containment only

Set up of De-humidification equipment

Abrasive blast to Chemcote Standards

Application of a Chem-tect™ RF 300 in 3 coats including strip coat all difficult to reach areas

De-mobilise from site

PRODUCTS

Chem-tect™ RF 364 – vinyl ester / acrylic co-polymer enhanced with flaked glass; very suitable for immersed environments where superior resistance to chemical attack is required

OUTCOME

The best outcome the asset owner has obtained after years of trials using various epoxies and fibreglass linings. The combined large anchor profile achieved while abrasive blasting and excellent permeation resistance of the glass flake filler has proven itself again.

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