Metal Surface Preparation: How to Prevent Rust and Coating Failure

Metal surface preparation is one of the most important steps in any industrial metal coating project.

Even a high-performance coating can fail when it is applied over loose rust, mill scale, grease, soluble salts, trapped moisture, preparation dust, or an unstable existing finish. The completed surface may look acceptable at first, but adhesion problems can appear after exposure to rain, humidity, chemicals, abrasion, or temperature changes.

For contractors coating structural steel, equipment, tanks, metal buildings, railings, machinery, or architectural metal, preparation should never be treated as a quick cleaning step. It is the foundation of the entire corrosion-protection system.

This contractor guide explains how to prepare metal for coating, evaluate rust and existing finishes, select an appropriate preparation method, create the required surface profile, and reduce the risk of premature metal coating failure.

Why Metal Surface Preparation Matters

A protective metal coating creates a barrier between the substrate and the conditions that cause corrosion. Depending on the project, that may include moisture, oxygen, chemicals, salts, sunlight, abrasion, or repeated cleaning.

For the coating to provide that protection, it must form a strong and continuous bond with the substrate.

That bond can be compromised by:

• Oil and grease

• Dirt and construction debris

• Loose or layered rust

• Mill scale

• Soluble salts

• Moisture and condensation

• Welding residue

• Grinding or blasting dust

• Chalked paint

• Loose existing coatings

• Chemical contamination

• Smooth or glossy surfaces

• An incorrect surface profile

The objective is not simply to make the metal look clean. Proper metal surface preparation should leave the substrate clean, sound, dry, and appropriately profiled for the specified coating.

How Improper Preparation Causes Metal Coating Failure

When contamination or unstable material remains on a metal surface, the new coating bonds to that material instead of the sound substrate.

Common examples include:

• A coating applied over loose rust bonds to corrosion that is already separating from the steel.

• Oil and grease prevent the coating from making direct contact with the metal.

• Soluble salts beneath the coating attract moisture and can contribute to blistering and renewed corrosion.

• Condensation creates a moisture layer between the metal and coating.

• A glossy existing finish may not provide enough texture for mechanical adhesion.

• A surface profile that is too shallow may reduce adhesion.

• A profile that is too deep may leave peaks insufficiently covered by the coating.

• Dust left after grinding or blasting can become a weak layer beneath the coating.

These conditions may lead to:

• Peeling

• Blistering

• Bubbling

• Rust bleed-through

• Cracking

• Flaking

• Pinholes

• Poor adhesion

• Uneven coating thickness

• Corrosion around welds and edges

• Premature coating-system failure

Many of these problems can be prevented by inspecting, preparing, and documenting the metal before coating begins.

1. Identify the Metal Substrate

Before choosing a preparation method, determine what type of metal is being coated.

Common substrates include:

• Carbon steel

• Galvanized steel

• Aluminum

• Stainless steel

• Weathered steel

• Previously coated steel

• Factory-finished metal

Different metals require different preparation procedures. A process appropriate for heavily rusted carbon steel may damage galvanized metal, remove protective zinc, or contaminate aluminum.

Contractors should also determine:

• Whether the metal is new, weathered, or previously coated

• Whether oil, passivators, or factory treatments are present

• Whether the existing coating is known

• Whether the metal has been exposed to salts or chemicals

• Whether corrosion is visible beneath an existing coating

• Whether the surface contains pits, welds, seams, bolts, or sharp edges

• Whether the substrate is structurally sound

A coating cannot restore metal that has lost its required structural capacity. Severe pitting, perforation, or section loss should be evaluated before surface preparation and coating work proceeds.

2. Evaluate the Service Environment

Preparation requirements should reflect the conditions the metal will face after installation.

Before estimating or beginning the project, ask:

• Will the metal be indoors or outdoors?

• Will it be exposed to rain, humidity, or standing water?

• Is the project located in a coastal or high-salt environment?

• Will the metal experience frequent condensation?

• Are chemicals, fuels, oils, or aggressive cleaners present?

• Will the surface receive abrasion or impact?

• Will it be washed frequently?

• Is immersion or continuous moisture involved?

• Are elevated service temperatures expected?

• What coating life does the owner expect?

• Does the project specification require a particular preparation standard?

Structural steel inside a dry warehouse may not require the same level of preparation as exterior steel near the Texas Gulf Coast. Exposure severity, accessibility, maintenance cycles, and desired service life can all affect the required preparation.

3. Inspect and Document the Existing Surface

Complete a detailed inspection before cleaning begins.

Look for:

• Loose, layered, or flaking rust

• Tightly adhered rust

• Mill scale

• Corrosion pits

• Oil and grease

• Dirt and dust

• White rust on galvanized metal

• Oxidation on aluminum

• Salt or chemical exposure

• Weld spatter

• Sharp edges

• Crevices and overlapping metal

• Peeling or blistered coatings

• Chalking

• Cracks in existing coatings

• Rust developing beneath a coating

• Previous repairs

• Areas where water collects

Photographing and documenting the existing conditions can help establish the required labor, equipment, containment, and preparation standard.

It can also prevent contractors from discovering extensive coating failure or hidden corrosion after the project has already been priced.

Check for hazardous existing coatings

Unknown or older coatings may require testing and a project-specific hazard assessment before sanding, grinding, or abrasive blasting begins.

Abrasive blasting can create respirable dust and expose workers to hazardous materials contained in the abrasive or the coating being removed. OSHA specifically identifies abrasive blasting and power-tool cleaning of lead-containing coatings as activities that can create significant worker exposure. Contractors should use appropriate testing, engineering controls, containment, personal protective equipment, and regulatory procedures for the project. Review OSHA’s abrasive-blasting safety guidance.

4. Remove Oil and Grease Before Mechanical Preparation

Degrease the surface before grinding, sanding, wire brushing, or abrasive blasting.

Mechanical preparation performed over a contaminated surface can spread oil across the metal or force it into pits, seams, and other irregularities. The metal may look cleaner afterward while still containing residue that can interfere with adhesion.

Cleaning methods may include:

• Approved solvent cleaning

• Water-based degreasers

• Alkaline cleaners

• Commercial detergents

• Steam cleaning

• Pressure washing

• Repeated cleaning and rinsing

SSPC-SP 1 Solvent Cleaning defines an end condition in which visible deposits of oil, grease, and similar contaminants have been removed before coating or additional preparation. Review the official AMPP SSPC-SP 1 description.

Always confirm that the cleaner is appropriate for the substrate and the planned coating system.

If rinsing is required, remove all cleaner residue and allow the metal to dry completely. Residual cleaner can become another source of contamination.

5. Evaluate Soluble Salt and Chemical Contamination

A metal surface can appear clean while still containing soluble salts.

This risk is especially important for:

• Coastal structures

• Marine environments

• Bridges and transportation equipment

• Metal exposed to road salts

• Industrial plants

• Chemical-processing areas

• Previously submerged structures

• Equipment exposed to aggressive cleaners

• Steel subjected to repeated wetting and drying

Salts can remain inside corrosion pits and surface irregularities. When moisture reaches those contaminants beneath a coating, osmotic blistering and renewed corrosion may occur.

Abrasive blasting can expose salts trapped in pits, but blasting alone may not remove them. High-risk projects may require:

• Specified salt testing

• Washing procedures

• Retesting

• Documented acceptance levels

• Defined testing frequency and locations

Visual cleanliness standards address visible contaminants; they do not automatically verify that nonvisible soluble salts have been reduced to an acceptable level. AMPP maintains separate standards and guidance for nonvisible contaminants and soluble salt testing. Explore AMPP surface-preparation standards.

6. Remove Loose Rust, Mill Scale and Failed Coatings

Loose, powdery, layered, or flaking rust must be removed.

A coating cannot permanently stabilize corrosion that is already separating from the underlying metal. If the coating bonds to loose rust instead of sound steel, the coating and corrosion can detach together.

Rust-removal methods may include:

• Hand scraping

• Wire brushing

• Sanding

• Power wire brushing

• Grinding

• Needle scaling

• Bristle blasting

• Abrasive blasting

• Waterjetting when specified

Mill scale must also be evaluated. This hard oxide layer forms during the hot-rolling process used to manufacture steel. Although some mill scale may initially appear tightly bonded, unstable mill scale can separate and contribute to localized corrosion beneath a coating.

Loose or failed existing coatings must also be removed. Applying a high-performance coating over a weak existing layer does not strengthen the old coating. The complete system will remain dependent on its weakest layer.

7. Evaluate Existing Coatings Before Recoating

An existing finish should only remain when it is sound, clean, properly prepared, and compatible with the new coating.

Inspect existing coatings for:

• Peeling

• Blistering

• Cracking

• Chalking

• Softening

• Rust undercutting

• Chemical damage

• Poor adhesion

• Glossy or nonporous areas

• Multiple unknown coating layers

• Trapped moisture

Adhesion testing can help determine whether the existing coating is stable enough to receive another layer. A compatibility test area may also be necessary.

Sound existing coatings generally still need to be:

1. Thoroughly cleaned

2. Allowed to dry

3. Abraded to remove gloss

4. Cleared of sanding dust

5. Tested for adhesion and compatibility

If the existing finish lifts, wrinkles, softens, or loses adhesion during the test application, additional removal or a different system may be necessary.

8. Select the Required Preparation Method

The metal condition, coating requirements, jobsite limitations, and specified cleanliness level determine which preparation method should be used.

Hand-tool cleaning

Hand-tool cleaning may involve:

• Scrapers

• Hand wire brushes

• Sandpaper

• Chipping tools

• Non-powered abrasive pads

This method may be practical for:

• Small maintenance repairs

• Touch-ups

• Tight spaces

• Edges and corners

• Limited-access areas

• Projects where powered equipment is restricted

SSPC-SP 2 establishes requirements for removing loosely adhered detrimental material with non-powered hand tools. It does not necessarily produce bare metal or remove tightly adhered rust and mill scale. Review AMPP SSPC-SP 2.

Power-tool cleaning

Power-tool preparation may use:

• Angle grinders

• Power wire brushes

• Sanders

• Needle scalers

• Rotary impact tools

• Bristle-blasting tools

• Specialty surface-preparation equipment

SSPC-SP 3 addresses power-tool cleaning used to remove loose detrimental material. SP 3 does not require exposure of bare metal or establishment of a minimum surface profile. Review AMPP SSPC-SP 3.

When a roughened, clean, bare carbon-steel surface is required but abrasive blasting is not feasible, a specification may instead reference SSPC-SP 11 Power Tool Cleaning to

Bare Metal. Review AMPP SSPC-SP 11.

Contractors must avoid burnishing the steel. A shiny surface is not necessarily a properly prepared surface. If the tool polishes the metal too smoothly, the coating may not receive the profile required for adhesion.

Abrasive blast cleaning

Abrasive blasting is frequently specified for demanding industrial projects because it can:

• Remove rust and mill scale

• Remove existing coatings

• Clean corrosion pits

• Expose hidden defects

• Create a measurable anchor profile

• Produce a more consistent surface

Blast media and equipment should be selected according to:

• Metal type and thickness

• Required cleanliness level

• Required profile depth

• Existing coating thickness

• Planned coating thickness

• Containment requirements

• Environmental restrictions

• Abrasive recovery and disposal requirements

After blasting, inspect for remaining rust, mill scale, embedded abrasive, dust, oil, moisture, flash rust, and newly exposed pitting.

Common AMPP/SSPC Surface-Preparation Standards

Industrial coating specifications frequently reference AMPP/SSPC standards to define the required condition of prepared steel.

These standards describe an acceptance condition—not simply which tool should be used.

Standard	General purpose
SSPC-SP 1	Removal of visible oil, grease, dirt, and similar contaminants
SSPC-SP 2	Hand-tool cleaning of loose detrimental material
SSPC-SP 3	Power-tool cleaning of loose detrimental material
SSPC-SP 11	Power-tool cleaning to a roughened, bare-metal condition
SSPC-SP 7/NACE No. 4	Brush-off blast cleaning
SSPC-SP 6/NACE No. 3	Commercial blast cleaning
SSPC-SP 10/NACE No. 2	Near-white metal blast cleaning
SSPC-SP 5/NACE No. 1	White-metal blast cleaning

The required standard depends on:

• Project specifications

• Coating-manufacturer requirements

• Expected exposure

• Existing surface condition

• Desired service life

• Available preparation equipment

• Containment and environmental restrictions

Preparation standards should be established before the project is estimated. Near-white or white-metal blast-cleaning requirements can significantly affect labor, production rates, equipment, containment, and total project cost.

AMPP maintains the active standards for hand-tool, power-tool, abrasive-blast, waterjet, surface-profile, and nonvisible-contaminant preparation. View AMPP’s Surface Preparation Committee resources.

9. Create the Correct Surface Profile

Surface profile, also called an anchor pattern, is the microscopic texture created during blasting or mechanical preparation.

This texture increases the available surface area and helps the coating develop a mechanical bond with the substrate.

The required profile depends on:

• Coating type

• Primer requirements

• Coating solids

• Specified dry-film thickness

• Number of coats

• Service environment

• Manufacturer requirements

A profile that is too shallow may reduce adhesion.

A profile that is too deep can also cause failure. If the coating does not sufficiently cover the profile peaks, those points may receive inadequate protection and become early corrosion sites.

Profile depth can be evaluated using approved methods such as:

• Replica tape

• Profile comparators

• Depth micrometers

• Digital surface-profile gauges

Abrasive type, particle size, pressure, equipment settings, application angle, and operator technique can all affect the finished profile.

10. Detail Edges, Welds, Bolts and Crevices

Metal coating failure frequently begins in difficult areas rather than across the center of a flat panel.

Pay close attention to:

• Sharp edges

• Corners

• Weld seams

• Weld spatter

• Bolts and fasteners

• Corrosion pits

• Overlapping metal

• Connections

• Crevices

• Drainage points

• Areas where water collects

Liquid coatings can pull away from sharp edges during application and cure, leaving less protective film than on flat surfaces.

Preparation may require:

• Removing weld spatter

• Smoothing rough welds

• Rounding sharp edges when specified

• Cleaning corrosion from pits

• Addressing fabrication defects

• Removing sharp projections

• Cleaning seams and crevices

• Keeping drainage paths open

The project specification may also require a stripe coat around welds, edges, bolts, and other difficult areas. That requirement should be identified before coating application begins.

11. Prepare Galvanized Metal and Aluminum Correctly

Galvanized steel

Galvanized steel has a zinc layer that protects the underlying metal. Preparation should improve coating adhesion without unnecessarily removing that protective layer.

New galvanized surfaces may contain:

• Oil

• Fabrication residue

• Passivators

• Chemical treatments

• Smooth areas that reduce adhesion

Weathered galvanized metal may also develop white rust or zinc corrosion products.

Preparation may include cleaning, degreasing, removing white rust, light abrasion, or specified brush-off blasting. SSPC-SP 16 addresses brush-off blast cleaning of coated and uncoated galvanized steel, stainless steel, and other nonferrous metals. Review AMPP SSPC-SP 16.

Avoid aggressive grinding that unnecessarily removes the zinc layer.

Aluminum

Aluminum does not develop red rust like carbon steel, but it can oxidize and corrode.

Before coating aluminum:

• Remove oil and grease

• Remove loose oxidation

• Clean the surface thoroughly

• Abrade it using an approved method

• Avoid polishing it too smoothly

• Remove all preparation dust

• Use tools suitable for nonferrous metal

• Prevent carbon-steel contamination

Whenever practical, use clean abrasives and tools dedicated to aluminum. Steel wire brushes or contaminated media can embed carbon-steel particles that later rust and stain the surface.

12. Remove Dust and Abrasive Residue

Grinding, sanding, and blasting leave fine dust on the prepared surface.

If that dust is not removed, the coating may bond to the dust instead of the metal.

After preparation:

• Vacuum the surface using appropriate industrial equipment

• Remove accumulated abrasive

• Inspect horizontal ledges

• Check pits, seams, welds, corners, and bolt heads

• Remove fibers and cleaning residue

• Use clean, dry compressed air only when permitted

Compressed air should be checked for oil and moisture. Contaminated air can reintroduce residue onto an otherwise clean surface.

Do not use an unapproved solvent as a final wipe. The solvent, wiping method, and cloth can leave residue or move contamination around the surface.

13. Monitor Temperature, Humidity and Dew Point

Freshly prepared steel can begin rusting quickly when exposed to humidity or condensation.

Before coating, verify:

• Ambient air temperature

• Metal surface temperature

• Relative humidity

• Dew point

• Weather forecast

• Ventilation conditions

• Presence of condensation

• Product application limits

Metal temperature can differ from ambient air temperature. A steel surface may remain cool enough for condensation to form even when the surrounding air feels warm.

Environmental readings may need to be taken:

• Before preparation

• After preparation

• Before coating

• During application

• During the early cure period

Many specifications require the surface temperature to remain a stated amount above the dew point. Follow the coating technical data sheet and project specification instead of relying on one universal requirement.

This is especially important in humid Texas and Gulf Coast conditions, where weather and surface temperatures can change quickly.

14. Prevent Flash Rust and New Contamination

Once bare steel has been prepared, it becomes vulnerable to new corrosion and jobsite contamination.

Delays between preparation and coating can allow:

• Flash rust

• Condensation

• Dust accumulation

• Salt deposition

• Overspray

• Handprints

• Oil transfer

• Debris from nearby trades

Coordinate the preparation and coating crews so completed areas can be inspected and coated within the specified time.

If rust, moisture, or contamination returns before coating, the affected surface should be re-evaluated and prepared again as required.

Final Pre-Coating Inspection

Before mixing the coating, confirm that the prepared surface meets the project requirements.

Check the following:

1. Cleanliness

   Has the specified preparation standard been achieved across the entire surface?

2. Surface profile

   Does the anchor profile fall within the required range for the coating?

3. Dust and abrasive

   Have preparation dust and blast media been removed from ledges, pits, corners, welds, and fasteners?

4. Oil and grease

   Is the surface free of visible contamination and cleaner residue?

5. Soluble salts

   Were required tests completed, documented, and accepted?

6. Existing coatings

   Is every remaining coating area sound, clean, abraded, and compatible?

7. Detail areas

   Have sharp edges, welds, bolts, seams, pits, and crevices been properly addressed?

8. Environmental conditions

   Are the air temperature, surface temperature, relative humidity, and dew point within the specified limits?

9. Moisture

   Is the metal completely dry and free of condensation?

10. Timing

Can coating application be completed before flash rust or new contamination develops?

Documenting the final conditions provides a record that the surface was inspected and accepted before coating began.

Common Metal Surface Preparation Mistakes

• Grinding before degreasing

  Grinding can spread oil and grease or force it into pits. Remove contamination before beginning mechanical preparation.

• Coating over loose rust

  Loose rust is already separating from the metal. A new coating applied over it may detach with the corrosion beneath it.

• Assuming DTM means no preparation

  Direct-to-metal coatings still require an approved surface condition. DTM does not mean a product can be applied over grease, loose rust, salts, dirt, moisture, mill scale, or failed paint.

• Leaving preparation dust behind

  Fine dust creates a weak layer between the coating and substrate. Clean the surface thoroughly after grinding, sanding, or blasting.

• Polishing the steel too smoothly

  Certain wire wheels and grinding methods can burnish the metal. A shiny surface may not provide the required anchor profile.

• Ignoring soluble salts

  Salt contamination is not always visible. Coastal, marine, transportation, and industrial projects may require testing, washing, and documentation.

• Recoating an unstable finish

  A new coating cannot correct poor adhesion underneath an existing layer. Loose, peeling, or incompatible material must be removed.

• Overlooking edges and welds

  Rust frequently returns around bolts, pits, welds, and sharp edges because these areas were not completely cleaned or did not receive sufficient coating thickness.

• Preparing too far ahead

  Bare steel left exposed can develop flash rust or collect new contamination before coating begins.

• Guessing environmental conditions

  A surface can appear dry while condensation is present. Surface temperature, humidity, and dew point should be measured.

• Treating every metal the same

  Carbon steel, galvanized steel, aluminum, stainless steel, and previously coated metal have different preparation requirements. Using the wrong process can damage the substrate or reduce adhesion.

Contractor’s Metal Surface Preparation Checklist

Before coating, confirm that:

• The metal substrate has been identified

• The service environment has been evaluated

• Structural deterioration has been addressed

• Hazardous existing coatings have been evaluated

• Oil and grease have been removed

• Cleaner residue has been removed

• Soluble salt risks have been assessed

• Required salt testing has been completed

• Loose rust and mill scale have been removed

• Failed existing coatings have been removed

• Remaining coatings are sound and compatible

• The specified cleanliness standard has been achieved

• The required surface profile has been created

• Profile measurements have been documented when required

• Grinding and blasting dust have been removed

• Abrasive residue has been removed

• Welds and weld spatter have been addressed

• Sharp edges and corners have been inspected

• Bolts, pits, seams, and crevices have been cleaned

• Air and surface temperatures are acceptable

• Relative humidity and dew point have been checked

• The surface is dry and free of condensation

• The metal can be coated before flash rust develops

• A compatibility test area has been completed when necessary

• The final surface has been inspected and accepted

Surface Preparation Is the Foundation of Corrosion Protection

Rust prevention begins before the coating container is opened.

Contractors must identify the substrate, understand the exposure, remove contamination, eliminate unstable corrosion, create the required surface profile, and confirm acceptable environmental conditions.

The appropriate preparation method may range from hand-tool cleaning for a small maintenance repair to near-white or white-metal abrasive blasting for demanding industrial service.

Regardless of the method, the objective remains the same: create a clean, sound, dry, and properly profiled surface that allows the coating system to perform as designed.

Reducing preparation may lower the initial installation cost, but it can increase the risk of callbacks, premature rust, coating removal, replacement labor, and disruption to the customer’s facility.

Successful industrial metal coating projects start with preparation that is planned, measured, inspected, and documented.

Industrial Metal Coating Support for Texas and Louisiana Contractors

Platinum Concrete Coatings of Texas supports contractors, facility managers, architects, engineers, and project teams throughout Texas and Louisiana.

Our team can assist with:

• Surface-preparation requirements

• Technical data sheets

• Product specifications and submittals

• Primer and finish-coat compatibility

• Rust and corrosion-control projects

• Material planning and estimating

• Contractor product support

• Architect and engineer specification assistance

Every metal coating project should be reviewed individually. Preparation requirements depend on the substrate, existing condition, service environment, specified coating, application conditions, and expected service life.

Planning a structural steel, equipment, tank, metal building, railing, or industrial maintenance project?

Contact Platinum Concrete Coatings of Texas to review the project requirements before ordering or applying your coating system.

📍 18703 W Little York Road, Suite 103, Katy, TX 77449📞 (832) 593-6096🌐 www.platinumcoatingsoftexas.com

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Frequently Asked Questions About Metal Surface Preparation

• Does all rust need to be removed before coating metal?

Not every coating requires completely bare metal. However, loose, flaking, layered, and powdery rust must be removed. Any remaining tightly adhered rust must be permitted by the coating manufacturer and project specification.

• Should metal be cleaned before grinding?

Yes. Oil, grease, and similar contaminants should be removed before grinding, sanding, power-tool cleaning, or abrasive blasting. Mechanical preparation can spread contamination or force it into surface irregularities.

• Is grinding enough to prepare steel for coating?

Grinding may be suitable for certain maintenance projects, but it must achieve the cleanliness and surface profile required by the coating and specification. Salt, mill scale, dust, pits, welds, edges, and difficult areas must also be addressed.

• What is the best way to prepare heavily rusted steel?

The appropriate method depends on the severity of corrosion, substrate condition, project environment, and coating requirements. Abrasive blasting is frequently specified for heavily corroded steel and demanding industrial environments. Power-tool cleaning or waterjetting may be appropriate for other projects.

• What is an anchor profile?

An anchor profile is the microscopic texture created by abrasive blasting or mechanical preparation. It increases the surface area available for bonding and helps the coating adhere mechanically to the metal.

• Can the surface profile be too deep?

Yes. If the profile is too deep for the specified coating thickness, the profile peaks may not receive adequate coverage. Profile depth must be matched to the coating system and required dry-film thickness.

• Why does rust return around welds and edges?

Welds, pits, bolts, and sharp edges can be difficult to clean and coat. Liquid coatings may also pull away from sharp edges, leaving less film thickness. Detailed preparation and any required stripe coat help protect these areas.

• Can new paint be applied over an existing metal coating?

Only when the existing coating is sound, clean, properly abraded, and compatible with the new coating system. Loose or deteriorated coatings must be removed. An adhesion or compatibility test may be required.

• How soon should blast-cleaned steel be coated?

Blast-cleaned steel should be coated within the time required by the project specification and before flash rust, condensation, dust, salts, or other contamination develops. The acceptable time can vary with environmental conditions.

• Is preparation different for galvanized steel?

Yes. Galvanized metal may contain oils, passivators, white rust, or a smooth zinc surface. Preparation must create the required adhesion without unnecessarily removing the protective zinc layer.

• How can contractors prevent flash rust after preparation?

Monitor humidity, surface temperature, and dew point; protect prepared steel from moisture and contamination; coordinate preparation with coating application; and coat the steel within the time permitted by the specification.