Coatings and Galvanizing

Paint Coatings

We specialize in testing and evaluation of paints/protective coatings, accelerated weathering (QUV, salt spray, Cabinet Testing), and failure analysis of failed paints and coatings. We also offer expert witness testing, verification, and litigation support to settle liability disputes.We test  barrier and corrosion resistance properties of paint and coatings. Performance testing of paints and coatings to determine physical and mechanical properties prior to application is one of the most important procedures that can be performed to ensure the proper paint or coating has been selected for an intended service environment.A major consideration for most coating processes is that the coating is to be applied at a controlled thickness. 

Our experienced and certified  specialists perform the laboratory testing, on-site investigation and failure analysis. Special techniques are required to be able to analyze a paint failure. These range from  cross section microscopy, determination of plane of delamination and analysis of individual paint layers to determine if the paint system and surface preparation meets the specification requirements and if deviation has contributed to paint failure and accelerated corrosion. the following micrographs exhibit some of our capabilities. 

 

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Magnified image of a coating system consisting of three layer paint.

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Paint and coating failure due to improper surface preparation

912-90656-3 STR A4 Area with No Zinc Corroding   912-90656-3 STR B12 Area with No Zinc Corroding 

The above micrographs show uniform(left) and non-uniform(right) zinc rich paint that failed in service

A coating is a covering that is applied to the surface of an object, referred to as the substrate. The purpose of applying the coating may be decorative, barrier, or both. The coating itself may be an all-over coating, completely covering the substrate, or it may only cover parts of the substrate. An example of all of these types of coating is a product label on many drinks bottles- one side has an all-over functional coating (the adhesive) and the other side has one or more decorative coatings in an appropriate pattern (the printing) to form the words and images.
Functional coatings may be applied to change the surface properties of the substrate, such as adhesion, compatibility, or wear resistance. In other cases, such as semiconductor device fabrication (where the substrate is a wafer), the coating adds a completely new property such as a magnetic response or electrical conductivity and forms an essential part of the finished product.

 

 

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 Image13 - cross section SEM images-3

On top, photomicrograph showing the cross sectional characteristics,  paint layers and  improper surface preparation that resulted in accelerated corrosion of substrate. The Bottom picture shows the elemental composition in corroded area.

Following section summarizes our capabilities in paint/coating selection and failure analysis.

  •  Field Assessment of Coated Structures: Pipelines, T&D Structures and Construction Application
  •  Coating Selection and Coating Specifications Requirements for Industry and Construction Application

Exposure Tests and Adhesion Testing

  • Wet and Dry Adhesion Testing per ASTM and SSPC standards
  • Cabinet Testing : ASTM G 85, B117…etc. and EIS
  • Cathodic Dis-bondment Testing
  • Long Term Testing: Immersion and Cyclic Tests Per ASTM/NACE Standards
  • Electro-chemical Impedance Spectroscopy after and prior to exposure
  • UV and Humidity/Moisture Testing
  • Soil/Water/Concrete Exposure Tests and Corrosion Monitoring

Failure Analysis and Root Cause Determination of Coatings

  • Mechanical Damage and External Forces
  • Application Related
  • Surface Preparation Related
  • Substrate-Related
  • Coating Selection Related
  • Formulation Related

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We can perform various testing to determine the root cause for coating failure in your specific application. The investigation includes onsite assessment and laboratory failure analysis. Our coating experts have many years of experience in field evaluation and analysis of protective coatings including painted galvanized steel.

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Galvanized Steel and Failure Analysis

Hot dip galvanizing has been an attractive and economical means of corrosion protection for construction, utility tubular and lattice structures. Galvanized steel components are protected from corrosion attack due to both barrier effect and also due to galvanic (sacrificial) action of zinc. Zinc does a fine job of protecting a steel components  in moderately corrosive and extremely  corrosive environments. It provides long term protection both above ground and underground portion of structures . We have inspected galvanized roofs, galvanized pipes, galvanized lattices in service which date back to early 20th century. Upon inspection we found out that galvanized layer is present even after 100 years of service. The key point in long service life is that the soil in that location provided the protective layer on galvanized surface. However, both  white rust and paint failures have been observed  on galvanized steel components in service after few years in service.

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Not all galvanizing facilities are the same, however, and some times the quality of the galvanized layer is compromised due to lack of QC in the process. The production of high quality galvanized steel strctures depends on the metallurgical reaction between steel and molten zinc. The micro-structural characteristics, grain structure (spangle formation), surface segregation and corrosion of galvanized coatings depend on both steel and bath compositions, coating processes and post-coating processing. Factors often associated with corrosion failure of galvanized steel components are improper thickness, excessive brittle inter-metallic alloy layer, galvanizing, substrate surface preparation if coated, storage conditions, water/air/soil service conditions, or unsuitable coating selection  for corrosive applications.

Upon your request we can inspect and assess your galvanized steel components both in field and laboratory and determine the primary cause for accelerated corrosion or cracking.

Protective Coating Failure  Analysis Root Cause Investigation-Our Approach

Once it has been determined that a failure has indeed occurred, the plane of delamination and point corrosion initiation  must be found, and a determination must be made as to whether the failure occurred as a result of improper paint selection, surface preparation, paint application, service conditions, mechanical damage, corrosive environment, or from a deficiency in the specification requirments. When the point of origin is located, the investigation may proceed to a study of how the paint failure occurred, possible causes or factors in the paint  failure, and possible preventative measures.

Why a failure occurs is an important question in the method of evaluation. Cause of failure is that which can be fixed or changed to prevent future failures. Each question provides important clues to the investigation, and although priorities may be quite different, each question must be addressed and resolved to determine why a paintt failure may have occurred.

Our failure analysis procedure, or methodology for evaluation, will be  provided in a step by step approach. This includes justification for conducting a paint failure analysis investigation, developing a logical plan for the investigation to follow, collection of background information, specification requirements, sample removal techniques, on-site inspection, laboratory testing and analysis, and the formulation of a final report based on relevant factual data, analysis, and recommendations.

Your input is vital for our failure analysis root cause determination. By giving us a detailed description of the paint failure if available, you can be sure that all aspects of your paint problems will be considered promptly. We’ll send you a proposal for your work/project, including methods, testing, specific recommendation  and costs. 

Please call Dr. Mirshams at (469)-964-4040 to discuss the investigation.