CURSO 7

Corrosion blistering can be classified in two main groups: osmotic and non-osmotic.

Osmotic blistering can be caused mainly by:

• Surface soluble contaminants.
• Solvent retention in the coating.
• Contamination.
• Adverse environmental conditions.

Non-osmotic blistering ccan be caused by:

• Electro endosmosis.
• Cathodic reactions.
• Desprendimiento catódico.
• Temperature gradient.
• Stress by compression.

The impact of blisters in the coating of a structure depends on many factors such as volume and density per area, the type, the cause and the environment to which this structure is exposed.

Analysing the causes and the impact of blisters in the coating of a structure requires knowledge, analytical resources and experience.

For more information please contact our technical department in Optimiza or gain knowledge about coating failures here:

Excess thickness in coatings can lead to coating failures and have consequences such as:

• Solvent retention
• Bubbles.
• Dryness and curing problems.
• Stress and brittleness.
• Cracking.
• Wrinkling
• Extra cost.
• Delays in project planning.
• Visual defects.

Sometimes in industrial projects, excess thickness is not considered and the risk that involves is ignored. Depending on the type of coating, the environment to which the structure will be exposed, and the durability expected, excess of thickness can have serious consequences on a coating protection project.

Analyzing the causes and impact of blisters on the coating of a structure requires knowledge, analytical resources and experience.

For more information please contact our technical department in Optimiza or gain knowledge about coating failures here:

Coating specifications identify the property requirements of a coating project related to corrosion and/or visual protection of a structure or element.

Sometimes specifications are ambiguous, confusing and unclear which can lead to premature failure of the coating, meaning the painted structure or element can fail before the durability expectations of the client. Some of the failures related to coating specifications in a project can be due to, among others:

• Failure to analyse and understand the environment of the structure.
• Failure to clearly specify the durability expectations of the system until the first maintenance.
• Failure to select the appropriate coating systems for each specific element and environment.
• Selecting coatings without demanding qualification tests and/or quality assurance.
• Unclear surface preparation requirements and acceptance criteria.
• Unclear coating application requirements and acceptance criteria
• Awarding contracts without guaranteeing the qualification and the capacity of the contractor.
• Failure to establish minimum requirements for the area and work zone. Workshop and work site.
• Failure to establish qualification requirements for the personnel according to the work required.
• Failure to establish adequate requirements for quality control and inspection personnel.
• Not considering the inconvenient that the design of a structure can caused.
• Lack of an inspection and test plan that guarantees compliance with specifications.
• Failure to establish appropriate communication channels.

In the coating industry, a duplex system is one formed by a hot-dip galvanized coating and an organic coating system, in order to combine both systems to offer a durability better than the one they offer separately. The lack of understanding in the operation of these systems when combined can lead to premature failures in the coating, meaning the painted structure or element can fail before the durability expectations of the client.

Some of these failures can be related to:

• Failure to analyse and understand the environment of the structure.
• Failure to clearly specify the durability expectations of the system until the first maintenance.
• Failure to select the adequate coating system for the duplex system.
• Selecting coatings without demanding qualification tests and/or quality assurance.
• Failure to specify the adequate cleaning level of the surface.
• Imperfecciones y defectos en el galvanizado.
• Permeabilidad en el recubrimiento orgánico.
• Removal of galvanized protection due to an inadequate surface preparation.
• Imperfections and defects in galvanized.
• Permeability in the organic coating.
• Incompatibility of the coating with alkaline surfaces.
• Lack of cleaning between the galvanized surface and the organic coating.
• Qualification of personnel and contractor. Lack of experience in the application of duplex systems.
• Lack of an inspection and test plan that guarantees compliance with specifications.
• Inadequate specification for the duplex system project.

Coating failures can be natural, the coating fails when its durability expectancy has been exceeded; or premature, when the coating fails in service without achieving the durability expected for different causes and reasons. This could lead to:

• Accelerate the corrosion or degradation process of a structure.
• Increase the risk of failure in a structure or element.
• Less protection of the coating system, loss in the investment of the system.
• Higher maintenance cost.
• Premature replacement of the system. Increase non-quality costs.
• Delays in project planification and delivery.
• Loss of confidence, image and credibility with the client.
• Loss of contracts due to premature failure.
• Extra costs and loss of competitiveness.
• Claims of thousands of euros and sometimes millionaire losses.

Analysing coating failures to be precise on the causes that have caused them and to prevent them in the future, requires the investigation team to be qualified and with experience, and having adequate analytical resources for a correct interpretation of the case.

For more information please contact our technical department in Optimiza or gain knowledge about coating failures related with specification here.