Where corrosion is concerned, guessing may lead, not surprisingly, to the wrong solution. Even within the same production unit you are dealing with a variety of process conditions, installations and equipment and thus a wide range of potential corrosion types and sources. Most of the time, measures against corrosion are based on the wrong cause(s) or are based on a wild guess.

For instance, when corrosion occurs under a coating, the maintenance department may think that local repair of the coating is the obvious thing to do. But it is likely that the specific type of coating used was in fact wrongly chosen for the process conditions given, or that just coating was poorly prepared by the applicator. This is usually the cause when paints fail.

Changed process conditions

Another example: pit corrosion is occurring in a 25 meter chimney on a carbon steel part just below the 5 meter stainless steel top. To save energy, the process engineers had decided to decrease the process temperature from 98 deg C to 93 deg C resulting in a change of dew point causing the carbon steel to corrode and seriously damage the chimney.

Fig 1: Stress corrosion cracking

In addition to a support to prevent the chimney from leaking and breaking, the chimney was repaired by cladding. But you can bet on it that the change of process temperature will not only cause corrosion in the chimney, but in many other parts and equipment in the installation as well.

Site management should ask themselves the question whether the savings in energy outweigh the additional cost of corrosion damage. Most probably the reply is negative. So in this case, the best solution is to reconsider the temperature change or anticipate corrosive conditions requiring different materials and protective measures.

Corrosion is a multidisciplinary problem

Apart from the need to first determine the type of corrosion (there are 6 basic types and up to 15 others!), the cause of most the common corrosion problems can be found in (a combination of ): wrong material selection in relation to the process conditions; engineering faults, construction faults, modified process conditions, corrosive environment, chemical corrosion attack, microbiologic induced corrosion, maintenance faults, mistreatment of stainless steel, wrong metal surface protection, wrong pre-treatment for coating systems, corrosion under (damaged) insulation, corrosion under deposits...

There are numerous solutions against the large variety of corrosion types and possible causes. But if you do not know how to determine the type of corrosion and you have to guess when it comes to the cause, how on earth can you be sure about a remedy?

Fig 2: Microbiologic Induced Corrosion

One thing is certain, if you are in doubt and you seek help for your corrosion problem, any supplier will recommend you their own solution. But this solution (relevant or not) can never be more than just a single piece of the puzzle if you have failed to look at the total picture. It is therefore unrealistic to expect that one single party is able to take into consideration all relevant parameters and at the same time include all possible causes and appropriate solutions.

Corrosion is nearly always a multidisciplinary problem and if you want the solution to be permanent, it should be managed by a multidisciplinary team of specialists rather than just one, whatever his or her skills are. If you decide to manage the job yourself and subcontract the various specialisms, be aware that no one will take responsibility for bad results except for yourself. Such an approach is not very efficient and rarely leads to a structural solution.

For best results, it is essential that all the various specialisms involved (metallurgist, process engineer, chemical analyst, coating inspector etc.) exchange information during the survey and analysing process, agree on the final approach and closely cooperate during execution. If you do not succeed in organizing this cooperation between the specialists, or if the people involved are not prepared to actively share know how, they will surely start pointing the finger at each other when it goes wrong, with yourself and your organisation the victim caught somewhere in the middle.

Corrosion control technology alliance

You would be better off mobilizing the required expertise in your own company if possible, but nowadays it is very unlikely that these resources are available as technicians with the proper materials expertise are getting quite rare. The same counts for suppliers with all the necessary skills on board. They simply do not exist, unless they subcontract.

Fig 3: Pit corrosion in carbon steel pipe

But then again, you will not have the required result as full cooperation and exchange of know how will not happen. For this very reason the Corrosion Control Technology Alliance was founded.

This unique Dutch-Belgian coalition of independent specialists has already existed for four years now. In close cooperation with each other they analyse, exchange information, expertise and know how, develop a strategy, and work closely together during the execution phase resulting in a constructive and effective solution.

With your own process conditions as a starting point, the Corrosion Control Technology Alliance provides adequate material recommendations, process and (re)engineering, repairs and preventive technology. This is the best way to guarantee long-term corrosion-resistant durability. Referring to the above-mentioned multidisciplinary team, the following skills were added to complete the alliance:

– Investigation of behaviour of materials and coatings in corrosive environments and processes

– Inspection and non-destructive testing to determine the nature and extent of corrosion damage, potential causes and solutions

– Laboratory testing and water treatment chemicals and equipment to avoid deposits in heating and cooling water circuits

– Corrosion-resistant process (re)engineering, design and construction

– Repair, by welding or cladding of metal components and process equipment

– Constructions and components made of Glass Fibre Reinforced Plastics and other plastics

– Metal surface treatments, stainless steel treatments, chemical and technical cleaning of systems

– Phenolic heat-cured coatings for components exposed to chemicals, corrosive materials, sea water and high temperature changes such as heat exchangers, piping, pumps and valves

– Dry air services and equipment to stop corrosion and fly rust during maintenance processes

Understand corrosion

Unfortunately corrosion in most cases does not always reveal itself as a brown rusty surface. Rust is not even corrosion, but can be a result of corrosion. Without proper training most people will not be able to distinguish or define corrosion types, let alone be able to interpret its cause and choose the most effective cure.

Due to a lack of knowledge about materials and corrosion mechanisms, maintenance technicians often cause corrosion themselves unintentionally. For instance by the mistreatment of stainless steel, construction faults, causing galvanic corrosion by combining the wrong metals etc.

The best start to developing awareness on how to prevent and cure corrosion in industrial, marine and offshore environments is to attend training courses on this subject. The alliance provides an extensive training programme on materials, corrosion and coatings. Training is provided in the Dutch, French and English language all over the world.

The author is the initiator of the Corrosion Control Technology Alliance in the Netherlands.

Frans van der Kolk

Managing Director,

Technotrans,

Institute for Technology Transfer BV,

kolk@technotrans.nl