Corrosion is often treated as a single problem — metal rusts, you deal with it. In practice, the word covers six distinct electrochemical and chemical attack mechanisms, each of which progresses differently, causes different damage patterns, and demands a different remediation approach. Misidentifying the type of corrosion on an asset leads to the wrong treatment, premature coating failure, and the same problem two years later.
This guide breaks down the six most common types of industrial corrosion, how to recognize each one, and what the remediation process actually looks like.
1. Uniform (General) Corrosion
Uniform corrosion is the most recognizable form — a consistent layer of oxidation spreading evenly across an exposed metal surface. It’s what most people picture when they think of rust: a reddish-brown coating that gradually thickens and eats into the base metal.
Why it develops: Uniform corrosion occurs when a metal surface is exposed to oxygen and moisture without adequate protective coating. Rate of progression depends on the environment — dry indoor conditions produce slow, shallow oxidation, while humid industrial environments, coastal proximity, or chemical exposure dramatically accelerate the process.
What it looks like in Michigan: Carbon steel structural members, tanks, and equipment left unpainted or with aged, failed coatings develop uniform corrosion across broad surface areas. Michigan’s seasonal humidity and condensation cycles — particularly in facilities with poor ventilation or temperature swings — accelerate progression significantly.
Remediation: Uniform corrosion responds well to abrasive blasting. Even heavily oxidized surfaces can be returned to clean, sound metal with the right blast media and sufficient abrasive energy. The critical variable is depth — surface oxidation cleans up quickly, while deep-pitted uniform corrosion requires more aggressive SSPC-SP 10 or SP 5 preparation to ensure no compromised steel remains beneath the coating.
2. Pitting Corrosion
Pitting corrosion is localized attack that bores narrow, deep holes into metal rather than spreading uniformly across the surface. It’s often more dangerous than uniform corrosion because the damage is concentrated — and because a surface with extensive pitting can look less corroded than it actually is.
Why it develops: Pitting occurs when the passive oxide layer on a metal surface breaks down at specific points, usually due to chloride ions, mechanical damage, or surface contamination. The exposed bare metal at the pit bottom becomes anodic and corrodes preferentially, while the surrounding passive surface acts as the cathode. The electrochemical imbalance drives rapid, localized attack.
What makes it serious: A pit’s depth-to-diameter ratio means significant section loss can occur beneath what looks like minor surface damage. On load-bearing structural steel, tank bottoms, or pressure-containing equipment, pitting that compromises wall thickness is a structural and safety issue — not just a cosmetic one.
Remediation: Blasting cleans corrosion from pit interiors, but cannot restore lost metal. After blasting, a coating inspection should assess whether pitting depth has caused meaningful section loss. High-build coatings can fill minor surface pitting and restore a more uniform surface profile, but pits indicating significant section loss on structural or pressure components warrant engineering review before coating proceeds.
3. Crevice Corrosion
Crevice corrosion occurs in confined spaces — gasket interfaces, lap joints, bolted connections, under washers, inside overlapping sections of structural steel — where oxygen is limited and moisture becomes trapped. It is one of the most common and least visible corrosion types in industrial steel construction.
Why it develops: In a crevice, oxygen is consumed but cannot be replenished from the surrounding environment. As oxygen depletion continues, the chemistry inside the crevice shifts — becoming acidic and chloride-enriched — which aggressively attacks the metal. The surrounding open surface, where oxygen is available, becomes cathodic and accelerates attack at the crevice.
Why it’s frequently missed: Crevice corrosion is entirely concealed by the joint or overlap that creates it. It’s often not discovered until a fastener shears, a lap joint separates, or a maintenance inspection probes areas standard visual inspection would miss. By the time it’s visible, significant section loss may have occurred.
Remediation: Mechanical cleaning cannot reach crevice interiors. Abrasive blasting with fine media — garnet or glass bead at appropriate pressure — can penetrate into accessible crevices, but deep or complex joint geometry may require disassembly for proper cleaning. Where disassembly is impractical, sealing accessible crevice edges with an appropriate sealant or coating system compatible with the joint design is the standard approach.
4. Galvanic Corrosion
Galvanic corrosion occurs when two dissimilar metals are in electrical contact in the presence of an electrolyte — typically water. The less noble metal (the anode) corrodes preferentially to protect the more noble metal (the cathode).
Why it matters in industrial settings: Dissimilar metal contacts are everywhere in industrial construction — steel structures fastened with stainless hardware, aluminum components attached to carbon steel frames, copper plumbing connected to steel pipe. In a dry environment, galvanic corrosion is negligible. In a wet or humid environment, it can destroy the less noble metal rapidly.
Common examples:
- Carbon steel fasteners through aluminum panels — the steel corrodes at the contact interface
- Stainless steel anchor bolts in carbon steel structure — the carbon steel corrodes around the bolt
- Copper pipe in contact with steel structure — steel corrodes at contact points
Remediation and prevention: Blasting removes existing corrosion at the galvanic contact zone and prepares both surfaces for protective coating. Critically, coating alone may not be sufficient if the galvanic couple remains intact and moisture is present — isolating the dissimilar metals with a dielectric gasket, tape, or coating barrier eliminates the electrical contact that drives the reaction. On new construction, design-level separation is the right answer; on existing assets, isolation plus protective coating is the remediation.
5. Microbiologically Influenced Corrosion (MIC)
Microbiologically influenced corrosion — MIC — is corrosion accelerated or caused by the metabolic activity of microorganisms. It’s most common in immersion environments, buried structures, wastewater systems, and processing facilities with regular water or organic product contact.
Why it develops: Sulfate-reducing bacteria (SRB), iron-oxidizing bacteria, and other microorganisms colonize metal surfaces and create localized electrochemical environments far more aggressive than the bulk fluid would produce. SRB, in particular, produce hydrogen sulfide as a metabolic byproduct — a compound that aggressively attacks steel even at trace concentrations.
Where it appears in Michigan industry:
- Wastewater treatment infrastructure — basins, clarifiers, pipe interiors
- Food and beverage processing equipment
- Tank bottoms with water accumulation
- Underground storage tank exteriors in contact with biologically active soil
Remediation: Removing MIC-damaged steel requires thorough blasting to bare metal, followed by application of a coating system specifically selected for microbial environments — typically a high-build epoxy or epoxy novolac lining. Coating selection for MIC-affected surfaces is more critical than for standard atmospheric applications; standard architectural or maintenance coatings are not appropriate.
6. Erosion Corrosion
Erosion corrosion occurs when the combined action of mechanical wear and corrosive attack removes metal faster than either mechanism would alone. The physical abrasion of the surface continuously strips away protective oxide layers and coating films, exposing fresh metal to the corrosive environment.
Where it occurs: Pipe elbows and bends carrying abrasive slurries or particulate-laden fluids, impeller housings, pump components, mixing equipment, and any surface subject to high-velocity fluid or abrasive particle impingement.
What it looks like: Erosion corrosion produces distinctive directional damage — grooves, channels, and horseshoe-shaped attack patterns that follow flow direction. It is often most severe at changes in flow geometry: inside bends, downstream of valves, and at injection points.
Remediation: Blasting prepares the surface, but coating selection is the critical variable here — standard protective coatings will not survive in an erosive environment. Ceramic-filled epoxies, elastomeric linings, and wear-resistant composites are specified for surfaces subject to erosion. For extreme environments, hard-facing or metallic overlays may be required. We work with coating manufacturers to identify appropriate systems for the specific abrasive and velocity conditions involved.
The Common Thread: Proper Surface Preparation
Regardless of corrosion type, the fundamental requirement before applying any protective coating is the same: the metal must be cleaned to the substrate, to a documented SSPC surface cleanliness standard, with the correct anchor profile for the specified coating system. No coating system — regardless of price or manufacturer specifications — performs to its design life over a contaminated or insufficiently prepared surface.
Identifying the type of corrosion you’re dealing with determines what preparation standard is required, what coating system is appropriate, and whether any structural or engineering assessment should precede the coating work. Getting that diagnosis right at the start saves money and prevents repeat failures.
Contact Blasting Jack to discuss the corrosion conditions at your facility and get a straightforward assessment of what proper remediation looks like.