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Corrosion-Resistant Handling Equipment Design for Marine Environments

Handling equipment in a shipyard, drydock, or waterfront plant works in marine atmosphere and, in places, in seawater itself, so corrosion is a design input from the first sketch rather than a paint question at the end. UTEC Industrial designs, engineers, machines, fabricates, and installs custom material handling systems for aerospace and heavy industry from its Spokane Valley, WA facility, integrating Allen-Bradley PLC and motion control with in-house CNC machining, heat treating, and stress relief. This article works through the problem from the owner's side: which parts of a machine sit in which marine exposure, how a site's corrosivity is classified, where corrosion concentrates on a machine, when it takes rigging gear out of service, how materials and coatings are chosen and documented, and what the sensors, drives, and controls need. Corrosion resistance is set along one chain, design → engineering → parts machining → fabrication → assembly → weld fatigue → stress relief → drives → controls → tuning → monitoring, and a crevice or an unprotected enclosure designed in at the first link shows up years later as a seized pin, a failed sensor, or a sling that has to be scrapped.

Which parts of a handling machine sit in which marine exposure?​

Marine exposure is not one environment. The ASM Handbook, Volume 13C, treats corrosion in seawater and corrosion in marine atmospheres in separate chapters. ISO 12944-2:2017, which classifies environments for protective paint systems on steel, also keeps the atmosphere apart from immersion: it defines atmospheric-corrosivity categories and describes separate categories for structures immersed in water or buried in soil.

A single piece of shipyard handling equipment can sit in more than one of those environments at once:

  • A marine railway cradle runs down into the water while its hauling winch and controls stay ashore.
  • A drydock or dock-edge transporter works in salt air all day and takes spray and runoff on its underside.
  • A block-turning fixture or shaft cradle works under cover but receives salt-laden parts, rigging, and air from outside.

The handbook's seawater and marine-atmosphere chapters each discuss their own set of variables, which the shipyard and marine handling overview summarizes. As engineering reasoning, the design response therefore starts by mapping which parts of the machine sit in which environment, not by choosing one coating for the whole machine (ASM Handbook Vol. 13C, 2006, chapters Corrosion in Seawater, pp. 27-41, and Corrosion in Marine Atmospheres, pp. 42-60; ISO 12944-2:2017).

How is the corrosivity of a handling equipment site classified?​

ISO 12944-2:2017, Classification of environments, is Part 2 of the ISO 12944 series on corrosion protection of steel structures by protective paint systems. It defines atmospheric-corrosivity categories based on the mass loss or thickness loss of standard specimens and describes typical natural atmospheric environments. It separately describes categories of environment for structures immersed in water or buried in soil.

The classification matters for handling equipment in three ways:

  • It is the input to the paint system. The standard states that the corrosion stresses associated with an environment or corrosivity category represent one essential parameter governing the selection of protective paint systems, so a specification that omits the category leaves the coating supplier to guess.
  • It differs across one machine. A marine railway cradle can need an immersion category for its lower frame and an atmospheric category for its upper structure.
  • It bears on the maintenance plan. As engineering reasoning, a coating system chosen for the category comes with its own inspection and repainting plan, so the handling equipment's inspection and repainting access has to be designed to suit that plan.

Table 1 of the 2017 edition includes an extreme atmospheric category, CX. A waterfront site's atmospheric category is established from that site's own exposure and stated in the specification, together with any immersion category, rather than assumed from a generic coastal label (ISO 12944-2:2017, Table 1).

Where does corrosion concentrate on a handling machine?​

On handling equipment, the corrosion design review goes feature by feature rather than surface by surface, starting with the places where a coating cannot be kept intact or an inspector cannot easily see:

  • Pinned and bolted joints. Pivot pins, clevis joints, and bolted splices are reviewed for whether each joint can be sealed or drained, and pin and bushing materials are chosen for the exposure. A pin that seizes in its bore turns a pivoting frame or a positioning axis into a rigid one and can overload its drive.
  • Press fits and bearing seats. Interference fits and bearing seats are reviewed for how they will be sealed in service. The crane-wheel library's axle-fretting and marine-corrosion articles treat these interfaces in detail for wheel assemblies.
  • Edges and weld toes. Edges that will be coated are radiused and weld profiles are detailed so the coating can cover them. On a frame that sees cyclic load, the weld toe is also where weld fatigue is assessed, which ties corrosion design directly to the weld-fatigue and stress-relief links of the chain.
  • Holding devices. On a marine railway, §1915.115(e)(1) requires the cradle or carriage to be positively blocked or secured in the hauled position so it cannot be accidentally released. A block, pawl, or latch that corrodes stiff defeats that requirement, so those parts need sealed pivots, corrosion-resistant pins, and a designed inspection point.

The design responses are the same across all four: avoid crevices where they are not needed, seal or drain those that remain, radius the edges that will be coated, and choose pin and bushing materials that will not seize in the exposure category (OSHA 29 CFR Part 1915, Subpart G-2026, §1915.115 paragraph e.1).

When does corrosion take rigging gear out of service?​

Rigging gear that works in salt air is exposed to corrosion that gear in a dry shop is not, and the removal rules name corrosion directly. OSHA's shipyard eTool lists the wire rope sling removal criteria of 29 CFR 1910.184(f)(5), under which a wire rope sling is removed from service immediately if any listed condition is present. The listed conditions include:

  • Ten randomly distributed broken wires in one rope lay, or five broken wires in one strand in one rope lay.
  • Wear or scraping of one-third of the original diameter of outside individual wires.
  • Kinking, crushing, bird caging, or other damage that distorts the rope structure.
  • Hooks opened more than 15 percent of the normal throat opening at the narrowest point, or twisted more than 10 degrees from the plane of the unbent hook.
  • Corrosion of the rope or end attachments, 1910.184(f)(5)(vii).

The eTool also names environmental deterioration among the typical causes of chain and chain-sling failure, and environmental conditions and chemical deterioration among the causes of fiber-rope and web-sling failure; a fiber rope sling showing discoloration or rotting is removed from service under 1910.184(h)(5)(v).

Marking is the second corrosion trap. Under §1915.112 and §1915.113, manila rope, wire rope, and chain slings and shackles must carry permanently affixed and legible manufacturer markings of their safe working load, and none may be used without those legible markings. A tag that salt, rust, or overpainting has made unreadable takes the gear out of use as surely as a broken wire does. OSHA's rigging guidance adds that slings must not be covered with permanent padding that would prevent inspection before each use, so any protective sleeve added against corrosion still has to leave the sling inspectable (OSHA eTool: Shipyard Employment, Materials Handling, Ropes, Chains, and Slings; OSHA 29 CFR Part 1915, Subpart G-2026, §1915.112 and §1915.113; OSHA Working in the Shipyard Industry: Rigging 2011, p. C-7).

How are materials chosen and documented for exposed and wetted components?​

Material choice follows the exposure map. Carbon steel structure in atmospheric service is protected by a coating system selected for its corrosivity category, while parts that cannot be kept coated, such as pins, bushings, wear pads, and fasteners in moving joints, are candidates for materials that resist the environment on their own.

Where a design calls for cast copper-base components, such as aluminum-bronze bushings or wear parts, ASTM B148-24 is the specification that covers sand castings in the aluminum-bronze alloys UNS C95200 through C95900, with inch-pound values as the standard units. Naming the specification and alloy on the drawing does two things: it fixes the chemistry and properties the casting must meet, and it gives receiving inspection something to check. The crane-wheel library's article on material documentation sets out what that documentation should contain, including heat numbers and measured chemistry.

Two design cautions go with mixed materials in seawater service:

  • Dissimilar-metal joints. A bronze bushing in a steel housing, or a stainless fastener in a coated steel plate, puts two different metals into one joint that seawater can wet, so the joint detail is reviewed for the metal combination and the metals are isolated where that review calls for it.
  • Coating continuity. A corrosion-resistant insert does nothing for the steel around it if the coating is broken at the insert's edge.

UTEC Industrial performs NDT and CMM inspection, so incoming castings and finished bores can be checked against the drawing before assembly (ASTM B148-24).

How are coatings and metallic coatings applied to marine handling equipment?​

Carbon steel handling structure depends on its coating system, and the ASM Handbook, Volume 13C, has a chapter on each family of coatings. Corrosion of Metallic Coatings discusses thermal spray, hot-dip, and electroplated coatings on steel, including aluminum and zinc coatings, and the corrosion attributes of the resulting coatings. Performance of Organic Coatings describes organic coatings as the principal means of corrosion control for the hulls and topsides of ships and for the splash zones on permanent offshore structures. ISO 12944-2:2017 supplies the corrosivity category, and it states that the corrosion stresses of that category represent one essential parameter governing the selection of a protective paint system.

For handling equipment, what the coating can achieve depends on decisions made at design and fabrication, before any paint is applied:

  • Coatable geometry. Edges are radiused and seams are continuously seal-welded so the coating has a surface it can cover; sharp edges, skip welds, and back-to-back angles are avoided on coated structure.
  • Drainage. Box sections, upward-facing channel flanges, and closed ends get drain holes or are detailed out, so they cannot hold seawater and salt against the steel.
  • Machined surfaces. Bearing seats, pin bores, and locating surfaces cannot carry a thick coating, so they need a temporary protectant during storage, sealing in service, or a corrosion-resistant insert.
  • Maintenance access. Every coated surface has to be reachable for inspection and repainting at the interval the maintenance plan for its corrosivity category sets.

As engineering reasoning, much of what a coating can do for a handling machine is therefore decided at the design and fabrication links, before the paint booth. The organic-coatings chapter adds that surface preparation is the most important consideration in determining the performance of organic coating systems (ASM Handbook Vol. 13C, 2006, chapters Corrosion of Metallic Coatings and Performance of Organic Coatings, pp. 69-72; ISO 12944-2:2017).

How does corrosion change inspection, maintenance, and energy isolation?​

Corrosion shortens the time between a sound component and a defective one, so equipment in marine service has to be easy to inspect and safe to service. The shipyard rules already set a demanding inspection rhythm: under §1915.111(a), all gear and equipment the employer provides for rigging and materials handling is inspected before each shift and, when necessary, at intervals during use, and defective gear is removed and repaired or replaced before further use. Under §1915.112(c)(2), chains in use receive a thorough inspection every 3 months, and each chain bears an indication of the month it was inspected. Equipment designed for marine service puts its pins, sheaves, hooks, and holding devices where an inspector can see them without disassembly.

Servicing corroded equipment also raises stored-energy hazards: a seized pivot that suddenly frees, or a holding brake with corroded linings. Energy control depends on who is doing the work:

  • Shipyard employment. 29 CFR 1915.89 requires a written lockout/tags-plus program for servicing machinery, equipment, and systems in landside facilities performing shipyard employment work and on vessels and vessel sections, where energization, startup, or the release of hazardous energy could endanger an employee. After October 31, 2011, energy-isolating devices must be designed to accept a lock whenever equipment is extensively repaired, renovated, modified, or replaced, or new equipment is installed, under paragraph (c)(5), with exceptions where the shipyard employer does not own the equipment or builds or services a vessel to customer specifications.
  • General-industry marine plants. A marine manufacturing plant outside shipyard employment follows 29 CFR 1910.147, which excludes employment covered by Part 1915 and which defines push buttons, selector switches, and other control-circuit-type devices as not being energy-isolating devices.

A lockable disconnect that corrodes shut or cannot be operated is no longer a usable isolation point, so isolators on marine equipment need enclosures and hardware chosen for the exposure (OSHA 29 CFR Part 1915, Subpart G-2026, §1915.111 and §1915.112; OSHA 29 CFR 1915.89-2011; OSHA 29 CFR 1910.147-1989).

What sensing and controls hold up in a marine environment, and how do they detect corrosion damage?​

In a salt environment, the sensors and controls are both at risk from corrosion and one of the tools for finding it early. The first job is survival: connectors, cable glands, limit switches, and encoders are exposed to spray and condensation, and enclosures for marine service are chosen for salt spray and washdown rather than for a dry plant. IEC 60204-1:2016+AMD1:2021 applies to the application of electrical, electronic, and programmable electronic equipment and systems to machines not portable by hand while working, starting at the point where the supply connects to the machine's electrical equipment.

The second job is detection. Corrosion shows up in a machine's behavior before it shows up as a failure:

  • Motor current. A servo drive such as Allen-Bradley Kinetix 5700 runs a current regulator loop on its motor, so the drive already measures the current each move takes. As engineering reasoning, a rising current trend for the same move can point to a stiffening pivot, a corroding bearing, or a seizing pin.
  • Following error and move time. A positioning axis that takes longer to reach position, or lags its command more, is meeting more friction than it did at commissioning.
  • Proven holding devices. On a marine railway, a switch that proves the cradle block or pawl is engaged before the winch brake can release turns the positive-blocking requirement of §1915.115(e)(1) into a permissive, and a switch that stops proving is itself a sign that the device needs attention.
  • Periodic logging. Logix 5000 tasks can be configured as continuous, periodic, or event, and a periodic task executes automatically at a preconfigured interval, so trending and diagnostic logic can run at a fixed period alongside the machine logic.
  • Safety functions kept separate. Emergency stop and guarded-zone functions run in a safety controller.

ISO 13849-1:2023 specifies a methodology and provides related requirements, recommendations and guidance for the design and integration of safety-related parts of control systems that perform safety functions, for high demand and continuous modes of operation. UTEC Industrial, a Rockwell Automation Recognized System Integrator, builds UL 508A control panels for the handling systems it fabricates (IEC 60204-1:2016+AMD1:2021; Rockwell Automation 2198-UM002E-EN-P, 2018, Kinetix 5700; Rockwell Automation 1756-RM094N-EN-P-2025; ISO 13849-1:2023; OSHA 29 CFR Part 1915, Subpart G-2026, §1915.115 paragraph e.1).

What should a buyer specify for handling equipment in marine service?​

A specification for marine service that says only "corrosion-resistant" gives the builder nothing to design to. A complete specification states:

  • Exposure map: the ISO 12944-2:2017 atmospheric category for each part of the site, the immersion category for any part that goes into water, and where spray, runoff, or wet-dry cycling reaches the machine.
  • Coating system: the system and durability required for each category, the surface preparation, and the repair procedure for field damage.
  • Materials: pin, bushing, fastener, and wear-part materials by specification and alloy, such as ASTM B148-24 aluminum-bronze castings where bronze parts are called for, with the documentation required at receipt.
  • Joint details: sealed or drained crevices, isolated dissimilar-metal joints, and protection for machined bearing and locating surfaces.
  • Rigging interface: legible, durable safe-working-load markings on every sling, shackle, and hook supplied, and an inspection plan for salt-exposed gear against the removal criteria.
  • Controls: enclosure ratings for salt spray and washdown, sealed connectors, proven holding devices, and drive-data trending for current and following error.
  • Energy control: lockable energy-isolating devices, consistent with §1915.89(c)(5) in a shipyard or 29 CFR 1910.147 in a general-industry plant.
  • Acceptance: coating thickness and inspection records, material documentation, and factory and site tests of every interlock.

UTEC Industrial performs factory acceptance testing and on-site commissioning, so these items can be written into the purchase order and demonstrated before the equipment ships to the waterfront (ISO 12944-2:2017; ASTM B148-24; OSHA 29 CFR 1915.89-2011; OSHA 29 CFR 1910.147-1989; OSHA eTool: Shipyard Employment, Materials Handling, Ropes, Chains, and Slings).

Related Articles

References​

  • Cramer, S.D., Covino, B.S., Jr. (eds.). ASM Handbook, Volume 13C: Corrosion: Environments and Industries. ASM International, 2006. ISBN 978-0-87170-709-3.
  • ISO 12944-2:2017: Paints and varnishes — Corrosion protection of steel structures by protective paint systems — Part 2: Classification of environments. International Organization for Standardization, 2017.
  • ASTM B148-24: Standard Specification for Aluminum-Bronze Sand Castings. ASTM International, 2024.
  • OSHA 29 CFR Part 1915, Subpart G-2026: Gear and Equipment for Rigging and Materials Handling. U.S. Department of Labor, 2026.
  • OSHA. eTool: Shipyard Employment — General Requirements — Materials Handling (including Gear and Equipment for Rigging). U.S. Department of Labor, 2026 (undated web documentation, accessed September 2026).
  • OSHA. Working in the Shipyard Industry: Rigging (Safety and Health Injury Prevention Sheets). U.S. Department of Labor, 2011.
  • OSHA 29 CFR 1915.89-2011: Control of hazardous energy (lockout/tags-plus). Occupational Safety and Health Administration, 2011.
  • OSHA 29 CFR 1910.147-1989: The Control of Hazardous Energy (Lockout/Tagout). Occupational Safety and Health Administration, 1989.
  • IEC 60204-1:2016+AMD1:2021 CSV (Ed. 6.1): Safety of Machinery -- Electrical Equipment of Machines -- Part 1: General Requirements. International Electrotechnical Commission, 2021.
  • ISO 13849-1:2023: Safety of machinery — Safety-related parts of control systems — Part 1: General principles for design. International Organization for Standardization, 2023.
  • Rockwell Automation 1756-RM094N-EN-P-2025: Logix 5000 Controllers Design Considerations. Rockwell Automation, 2025.
  • Rockwell Automation 2198-UM002E-EN-P (2018): Kinetix 5700 Servo Drives User Manual. Rockwell Automation, 2018.

Ready to Discuss a Material Handling System?​

UTEC Industrial designs, engineers, machines, fabricates, and installs custom material handling systems for heavy industry, from the stress-relieved structure and drives to the Allen-Bradley PLC controls, tuning, and monitoring that run them, at its Spokane Valley, WA facility. Send UTEC the application, loads, and duty cycle to start a system review.

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