On almost every industrial site we are likely to find hazardous chemicals – many of which are also corrosive.
Without proper mitigation of the effects of chemically-induced corrosion, assets such as pipelines, storage tanks and process vessels can degrade – eventually leading to leakage. This can introduce environmental issues and endanger personnel.
It is therefore paramount that asset owners take preventative steps to reduce the chances of leaking, and implement backup systems to contain any spillages that do happen.
Yet, each instance can vary depending on a combination of different factors.
Evaluating the Condition
Before deciding on the best strategy, it is important to understand the potential severity of the chemical attack.
The following factors are crucial when evaluating the conditions:
- Chemical and Concentration
- Temperature
- Exposure Time
- Combination of Threats
Overall, the most aggressive scenarios will be where there are highly-concentrated, corrosive chemicals in constant contact with an asset – especially if the temperature is elevated. Fluid flow, such as in pipelines, can also introduce additional wear mechanisms and when combined with the chemical attack, this can significantly increase the potential for rapid failure.
Protection Options
There are many options available to protect from chemical attack, all with their own merits and drawbacks.
- Good corrosion and chemical resistance
- Unable to repair like-for-like
- Prone to damage, linked to loss of adhesion
Rubber Linings
- Tough and durable
- Low adhesion
- Not practical to install on-site
- Difficult to repair
Metallic Cladding
- High performance
- Very high capital cost
- Time consuming and difficult to install
Coatings
- Simple to install and maintain
- Wide range of coatings available
- Performance varies
Polymer coatings are a popular choice across industry due to their ease of installation and maintenance, both at the new fabrication stage or on-site for existing equipment.
There is a wide range of coatings available on the market, which allows asset owners to select a solution that is optimised for their specific requirements. While this can be an advantage, the wide variety of coatings also introduces a risk for asset owners, due to the potential for improper product selection.
The challenge for coating manufacturers is to ensure asset owners receive the technical support both in material selection and installation – so that the performance expectations will be met.
Read more: Making It Stick: Optimising Adhesion
Three categories of coatings
Matching the solution to the unique conditions of each environment is hugely important. Based on their capabilities, chemical resistant coatings can be separated into three categories.
- Continuous Immersion at Ambient Temperatures - continuous immersion in hydrocarbons, methanol, sour gas, wet H2S & CO2 at ambient temperatures up to 60°C/140°F. As with the majority of these coatings, they are capable of withstanding the harsh effects of erosion and corrosion for the long term.
- Continuous Immersion at Elevated Temperatures - continuous immersion in hydrocarbons, methanol, sour gas, wet H2S & CO2 at elevated temperatures - specifically, over (203°F) and in some cases up to 160°C (320°F). These are ideally suited for processing environments, contitions you would expect to see e.g. in flare drums or desalters within the oil and gas industry. As the pictures point out, these have been successfully used for this type of equipment for a number of years and have been included in specifications for a number of major companies.
- Resistance to Aggressive Acids and Alkalis - resistance to a broad range of chemicals, including organic and inorganic acids. The coatings can accomodate for highly concentrated solutions, including sulphuric acid.
One example is the chemical resistant coating Belzona 4311, which has been used throughout industries for over 30 years. During that time, hundreds of applications have taken place, and here are a few examples of those from the most troublesome environments:
Coatings in Action
Chemical Plant
Problem:
The loading bay in question was required to handle contact with 98% sulphuric acid and the maintenance team for the site had installed a chemical resistant coating to protect the area. However, this coating could not handle exposure to the aggressive chemical concentration. The coating failed and the concrete underneath was being eaten away more and more during each spillage.
Solution:
Belzona´s distributor approached the plant with a solution to rebuild the area and coat for further protection. Application over the entire area was completed quickly, allowing the loading bay to get back into action with fit-for-purpose protection after several years of issues.
Prior to repair, after rebuild, and repaired and coated.
Pulp and Paper Plant
Problem:
Combinations of chemical attack and other damage mechanisms can have brutal effects on asset lifespans. This next example takes us to a pulp and paper plant whereby the additional force of abrasion was leaving this screw auger in dire need of repair. The option of replacing the equipment was considered but taking the cost and downtime into consideration made it unsuitable.
Solution:
Belzona 4311 was used in conjunction with a ceramic coating, to repair the screw auger on-site without disassembling. The speed of the cure and ease of application from both products meant that the auger could be returned to service quickly. After 8 years, the original coated auger was still in operation.
Copper Mine
Problem:
Leaking copper sulfate/electrolyte with 20% sulphuric acid had led to damage of the pump bases and containment area. This spalling had beed exacerbated further by the equipment vibration, jeopardising the copper production process.
Solution:
The pump bases were rebuilt, prior to being coated alongside the entire bund area. This was designed to prevent future damage via chemical attack and overall, reinstaded structural stability, ensuring rapid restoration of the copper production.
Refinery
Problem:
Vertical pumps handling 93% sulphuric acid had led to chemical attack inside the volute and on the impeller.
Solution:
The solution for acid pumps was originally tested and implemented on one pump in 1998. Following very satisfying results during inspection in 2005, this led to 5 identical pumps being protected with Belzona 4311, once more proving a very cost-effective maintenance solution.
Original pump after 5 years, rebuilt pump, fully rebuilt and coated impeller.
These different cases show that repair and prevention using polymeric coatings is a long-lasting and cost-effective solution compared to other forms of repair or replacement of the equipment in question, along with the associated costs of downtime.
Want more information about the Belzona 4311? Read more here.
