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Resolving erosion to hydroelectric power scroll case and stay vanes with Chesterton® ARC Industrial Coatings


Issue: Severe erosion had washed out previous lining after <6 months. Erosive flow damage was evident on exposed metal surfaces.

Goals: Install a protective coating with erosion resistance and high tensile adhesion capable of withstanding erosive flow and continuous immersion.

Root Cause: As water transitions from laminar to radial flow mechanical/erosion damage occurs at leading edges of stay vanes and outer race of scroll case.

Products featured in this case study:

  • ARC 858 – abrasion resistant rebuilding and faring composite
  • ARC SD4i – sprayable, ceramic reinforced coating

Chesterton ARC 858.

Chesterton ARC SD4i.


Grit blast to remove previous coating and create 75 μm (3+ mil) angular profile with a near white surface cleanliness.

ARC 858 used as a faring compound to fill in pitted and eroded sections prior to top coating with ARC SD4i. The ARC SD4i coating was applied to prepared metal and metal repaired with ARC 858 while ARC 858 was within overcoat window. A total 1.1 mm – 1.5 mm (45 – 60 mils) total DFT were applied in alternating colours for visual wear indications.

Scroll case and stay vanes after grit blasting.

Scroll case and stay vanes coated with ARC SD4i.

Final coat of ARC SD4i on stay vanes.

ARC 858 – 100% solids, thick film, ceramic reinforced abrasion control epoxy compound formulated to protect metal surfaces subjected to erosion, corrosion, and chemical attack.

ARC 858 industrial coating is designed to:

  • Upgrade new and old equipment exposed to abrasion, corrosion, or chemical attack
  • Rebuild surfaces with erosion resistant protection outperforming weld overlays
  • Fill grooves, pits, etc. in metal prior to overcoating with another ARC product
  • Easily apply by trowel​​​​

ARC SD4i – ​​​​​​​​100% solids, advanced reinforced thin film coating to protect structures and equipment in extreme immersion services.

ARC SD4i industrial coating is designed to:

  • ​Protect against corrosion and erosion
  • Provide extended protection in aggressive chemical immersion services
  • Apply by brush, roller, airless or plural component spraying


Client Reported: After 12 months in service, inspection revealed <.05% of coated surface area had seen coating damage, primarily tied to galvanic coupling at scroll case (CS) to wicket gate transition (SS).

This was compared to nearly 100% coating loss from previously applied system. Our client elected to coat second unit in a similar fashion in spring of 2022.

About Us

Chesterton® ARC coatings are specifically formulated and engineered to be used in a wide range of harsh environments and conditions.

With outstanding adhesion, superior mechanical strength, excellent permeation, chemical and wear resistance, 100% solids and solvent-free, the available range of Chesterton ARC coating will help you protect your investment.

® Registered trademark owned by A.W. Chesterton Company

Case study 162.  Issued 06/2022.  EN600850

Technical data reflects results of laboratory tests and is intended to indicate general characteristics only. A.W. Chesterton Company disclaims all warranties expressed or implied, including warranties of merchantability and fitness for a particular purpose. Liability, if any, is limited to product replacement only. Any images contained herein are for general illustrative or aesthetic purposes only and are not intended to convey any instructional, safety, handling, or usage information or advice respecting any product or equipment. Please refer to relevant Safety Data Sheets, Product Data Sheets, and/or Product Labels for safe use, storage, handling, and disposal of products, or consult with your local Chesterton sales representative.


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