Factory Direct Sale 2 Stage Small Hydraulic Cylinder

2 Stage Small
Telescopic Cylinder
Surface Treatments — Plunger Chrome + Barrel Finish

A telescopic hydraulic cylinder has two distinct surface treatment zones: the plunger (functional — affects seal life and performance) and the barrel exterior (protective — affects corrosion resistance and appearance). Understanding both zones helps you specify the right finish for your operating environment and your customer's expectations.

Hard chrome plating typically achieves 65–72 HRC surface hardness — significantly harder than the base steel of the plunger (typically 25–35 HRC). This hardness resists micro-scratching from dust particles that enter past the wiper seal. A scratched plunger progressively cuts the rod seal lip, leading to external leakage. The harder the plunger surface, the longer it resists this degradation.

Korea Ever-Power applies 20–30 µm (0.020–0.030 mm) of hard chrome to each plunger surface as standard. This thickness provides adequate wear life for typical dump truck service (3–5 years at normal duty cycles). For extreme-abrasion environments (quarries, mining) or extended service intervals, thicker chrome (40–50 µm) is available on request — adding 2–5 days to the production schedule for the additional plating time.

After chrome plating, the plunger surface is ground and polished to the target surface finish — the same cross-hatch specification required by the seal manufacturer. The chrome plating creates a slightly rougher surface than the base steel, so post-chrome grinding is essential to restore the finish to the correct range. Skipping this step (shipping with as-plated chrome) results in accelerated seal wear from the rough chrome surface — a common shortcut on low-quality cylinders.

Two-coat system: primer + topcoat. Standard colour is typically black or dark grey unless a custom colour is specified. Adequate corrosion protection for most applications where the cylinder is mounted under the vehicle and not directly exposed to saltwater or continuous chemical splash. This is the included finish — no additional cost.

Electrostatically applied dry powder, oven-cured to a hard, even finish. Thicker than paint (60–80 µm vs 25–40 µm), more resistant to chipping and scratching, and available in any RAL colour for brand matching. Powder coat is the preferred finish for OEM vehicle builders who want the cylinder to match the vehicle colour scheme and present a professional appearance to end customers. The higher impact resistance also makes powder coat practical for cylinders exposed to stone chips and debris from dump truck operations.

Can I skip the chrome plating to reduce cost?

No. A telescopic cylinder without chrome-plated plungers will fail within weeks — the bare steel plunger will corrode, scratch the seals, and develop surface pitting that causes permanent leakage. Chrome plating is included in every Korea Ever-Power cylinder as a non-negotiable standard. It is not a cost-reduction lever — it is a functional requirement. The only legitimate choice is the chrome thickness (standard vs heavy duty).

My previous cylinder's barrel paint peeled off within 6 months — why?

Paint adhesion failure is caused by inadequate surface preparation before painting — insufficient cleaning, degreasing, or blast profiling of the steel surface. The paint sits on top of a contaminated surface and peels away in sheets. Korea Ever-Power's paint process includes shot-blasting to SA 2.5 cleanliness before primer application — creating a mechanical key between the steel and the paint. If you have experienced paint adhesion issues with a previous supplier, specify "shot-blast + primer + topcoat" or upgrade to powder coat, which has inherently better adhesion due to the electrostatic application and thermal cure process.

Is zinc plating or powder coat better for coastal/marine environments?

Duplex (zinc + paint) is the best option for saltwater environments — the zinc provides sacrificial corrosion protection (protects even if the paint is damaged), and the paint provides the barrier layer. Powder coat alone is excellent for impact and appearance but does not provide sacrificial protection — once the powder coat is chipped, corrosion begins at the exposed steel. For marine-adjacent dump trucks and coastal construction, duplex zinc + paint or zinc + powder coat delivers the longest corrosion-free service life.

Does surface treatment affect the retracted length?

Negligibly. Chrome plating adds 20–50 µm to the plunger diameter (0.02–0.05 mm) — well within the bore clearance tolerance. Paint and powder coat add 25–80 µm to the barrel exterior diameter — which does not affect the internal dimensions or the retracted length. Surface treatment has no practical impact on cylinder dimensions or fit. The forklift cylinder range and aerial work vehicle cylinder range use the same surface treatment options.

We specified RAL 5010 (gentian blue) powder coat on the barrel to match our tipper brand colour. Ever-Power matched it perfectly — the cylinder looks like it was made by our company. The powder coat finish is noticeably harder than paint — after 8 months of construction site duty, no chips or scratches. The chrome plunger surface is smooth and mirror-bright even after 8 months of daily cycling. Appearance matters to our customers and the surface treatment quality delivers. 2-stage, 3-inch bore, 15 units.

Our dump trucks work on coastal construction sites — saltwater spray, sand, and high humidity year-round. We specified duplex treatment: zinc plating + paint on the barrel exterior, and heavy chrome (40 µm) on the plungers. After 10 months of coastal duty, no corrosion on any of the 8 cylinders. Our previous supplier's paint-only cylinders showed visible rust bubbles within 4 months in the same environment. The duplex zinc + paint is the right treatment for salt environments — well worth the 15% premium.

Ordered 2-stage cylinders for quarry dump trucks with standard chrome thickness (25 µm) and standard paint. Four stars because the standard chrome showed visible wear marks at 10 months in our extreme abrasion environment — the quarry dust is highly abrasive. I've now reordered with heavy chrome (45 µm) on the replacement batch. The standard chrome is fine for normal construction and road hauling, but quarry-grade abrasion needs the thicker option. The surface treatment guide on this page would have saved me the first order if I'd read it carefully — the 40–50 µm recommendation for extreme abrasion was correct.