Protecting Components Against Corrosion and Environmental Degradation
Most mining and industrial components spend their service life in environments that are actively hostile to bare metal surfaces — humid underground workings, outdoor stockpile and conveyor installations, marine port environments, and industrial facilities where process chemicals are present. A component that has been correctly cast, heat-treated, and machined will fail prematurely if its surface is not protected against the corrosion mechanisms present in its operating environment.
Surface treatment is the final stage of the production process before packaging and shipment. It is also the stage most visible to the client on receipt of the components — a poorly applied coating or inadequate surface preparation is immediately apparent and reflects directly on the quality of everything that preceded it. We apply surface treatment as a functional engineering step, not a cosmetic one.
Surface Preparation
Coating adhesion and long-term corrosion protection performance depend more on surface preparation than on the coating system itself. A primer applied over mill scale, rust, or contamination will delaminate — typically at the worst possible time, after the component is in service and inaccessible.
Standard surface preparation for painted components is abrasive blast cleaning to Sa 2.5 (near-white metal) per ISO 8501-1. This removes mill scale, rust, and existing coatings and creates a controlled surface profile (anchor pattern) that promotes mechanical adhesion of the primer coat. Surface profile depth is verified by replica tape measurement where coating system performance requirements specify it.
For components with complex geometry — internal surfaces, recesses, blind holes — cleaning method and coverage are specified at the engineering review stage. Internal surfaces that cannot be blast cleaned are treated by alternative methods appropriate to the geometry and corrosion exposure.
Coating Systems
Coating system selection depends on the operating environment, the expected service life before first maintenance, and client specification requirements. Standard systems applied include:
Primer + topcoat (epoxy or alkyd systems) — the standard system for most mining and industrial components for outdoor and moderate-humidity indoor service. Dry film thickness is specified per coat and verified by magnetic dry film gauge measurement after application. Total system DFT is typically 80–160 μm depending on the corrosivity category of the service environment (C3–C5 per ISO 12944).
Zinc-rich primer systems — for components in high-corrosivity environments (coastal, marine, or highly humid underground conditions) where galvanic protection of the steel substrate at coating damage sites is required. Zinc-rich primers provide cathodic protection at scratches and holidays in the coating; standard organic primers do not.
Phosphating — iron or zinc phosphate conversion coating applied before painting to improve coating adhesion and provide an additional corrosion barrier. Used as a standard pre-treatment for machined steel components where blast cleaning is not appropriate due to dimensional tolerance requirements.
Black oxide — for precision machined components where dimensional tolerance precludes coating thickness, and moderate corrosion protection in dry or lightly oiled storage and service conditions is acceptable.
For components where the client specifies a particular coating system — by product name, specification number, or DFT requirement — we apply the specified system. Where no coating specification is provided, we apply a system appropriate to the component type and service environment as described above, and confirm the selection with the client at order review.
Masking of Precision Surfaces
Machined bearing seats, seal faces, threaded interfaces, and other precision surfaces are masked before surface treatment to prevent coating contamination of dimensional features. Masking extent is defined at the engineering review stage based on the component drawing. Where coating is required on some but not all machined surfaces — for example, external painted faces with uncoated bearing bore interiors — masking specification is confirmed with the client before production.
Inspection and Documentation
Surface treatment inspection covers: blast profile (where specified), primer DFT after each coat, total system DFT after final coat, visual examination for runs, sags, holidays, and uncoated areas. Results are recorded per batch and retained as part of the production documentation. For components where coating inspection records are a delivery requirement, they are supplied with the shipment documentation.
For surface treatment specifications, coating system selection, or to discuss requirements for a specific operating environment, contact our engineering team.