Coating Inspection and Assessment

Surface coatings are an essential tool for fighting the billion-dollar problem of component degradation due to corrosion and other damage mechanisms. When designed, specified and manufactured correctly, coatings significantly extend component life for a relatively low cost. Unfortunately, perfect coatings are rarely guaranteed.

The ALS Approach 

When ALS steps in as your independent coatings advice partner, the below concerns can be confidently answered:

• Has my coating been correctly specified and applied?
• Why is my coating failing to stop corrosion?
• Why is my coating delaminating or blistering?
• Does the coating meet the manufacturing standard, including properties such as correct hardness and cure, adhesion and thickness?
• What surface preparation and atmospheric conditions must I achieve to successfully apply my coating?
• Does my coating have any defects in it, and if so how will these affect performance?
• Why did my coating fail?
• How can I successfully repair my coating so that it does not fail again?

Our staff are armed with specific coating expertise and utilise tailored inspection techniques to determine the important properties of a coating that can affect performance. Our NACE certified coating inspectors, scientists and engineers perform where competitors fail, providing visual inspection to relevant AS, AS/NZS, ASTM and ISO standard such as:

• AS/NZS 1580 set - paints and related materials – methods of test.
• AS 1627 set - including AS 1627.9 Pictorial surface preparation for painting steel surfaces.
• AS/NZS 2312.1 and AS/NZS 2312.2 - guide to the protection of structural steel against atmospheric corrosion by the use of protective coatings and hot dip galvanizing.
• AS 2331 set - methods of test for metallic and related coatings.
• AS 3894 – site testing of protective coatings.
• AS/NZS 4680:2006 - hot dip galvanized (zinc) coatings on fabricated ferrous articles.

ALS also provides:

• Comprehensive on-site and laboratory coatings testing including inhouse Scanning Electron Microscopy with Energy Dispersive Analysis (SEM/EDA) and Attenuated Total Reflectance/Fourier Transform Infra-Red, all provided under our ISO 9001 accredited quality systems.
• Technical consulting by our scientists and engineers who assist with understanding the root causes of coating failure, recommendations for corrective action and repair procedures where required.
• Coating selection advice with specific focus on the suitability of coatings for particular environments and specification of suitable application, inspection and maintenance programs.

Specific coating tests conducted by ALS are detailed below.

Epoxy Mix Ratio Testing

Epoxy based coatings fail on occasion due to incorrect ratios of the two parts that form the epoxy coatings. ALS provides testing to confirm the mix ratios of the in-service product, providing both a valuable quality control step to ensure that coating meet specifications and a valuable investigative technique to understand why the coating is not performing as expected.

Dry Film (Coating) Thickness Testing

Dry film thickness testing assesses the thickness of any surface coating present on a metallic component. This testing is to Australian and international standards.

Holiday (Continuity Testing)

Coated surfaces can have minor breaches not visible to the naked eye. Holiday testing applies a small current to the coated surface to detect such breaches. Testing is provided to standards such as:

• AS 3894.1- site testing of protective coatings - non-conductive coatings - continuity testing - high voltage ('brush') method.
• AS 3894.2- site testing of protective coatings - non-conductive coatings - continuity testing - wet sponge method.

Holiday testing can be performed on all coated surfaces with conductive substrates and provides a rapid scanning of coatings for defects frequently not visible to the naked eye.

Coating Adhesion and Peel Testing

The adherence of a coating to the material to which it is applied, known as the substrate, is critical to a coating’s performance. Separation or delamination at the interface between substrate and the coating can make the coating liable to cracking and also can expose a void that can preferentially fill up with corrosive materials such as moisture.

ALS performs testing, including peel tests, that confirm that correct adhesion has been achieved.

Surface Roughness Testing

Many coatings require not only a clean surface upon which the coating is applied but also a particular surface roughness to ensure that coating can bond to the surface effectively. ALS provides surface profile assessment to:

• AS 3894.5-2002 (R2013) - site testing of protective coatings.

Testing to this standard gives surface roughness values for Ra, Ry, Rz and Rq. Where needed, actual surface profiles can be assessed using metallographic examination by replication of specimen examination.