Below: the substrate is dry- but it is  darker (overall) than the original substrate.
This surface is dry within 5 minutes. The standard pictures in VIS-4 do not provide these types of illustrations of pressure-washed surfaces. The upper half is not washed; the lower half has been pressure washed.

Brush test on the Pressure Washed Surface.

Brush Test before Pressure Wash.

After Pressure Wash- there is very little faint color on cloth
After pressure washing the substrate, there is a faint marking at the upper edge of the cloth where the brush bristles contacted the surface.
The area has been mitigated from moderate to light flash rust.

 Prior to the application of paint, the substrate must meet the procurement specifications.
 Typical field remediation includes:
 Pressure washing
 Broom brushing
 Blowing off with pressurized air
 Solvent cloth or dry cloth wiping
 Vacuum

Upon polling contractors, it appears that pressure washing is the preferred practice. The appearance after pressure washing when the surface dries will be DIFFERENT; rust dust is washed away.  Typically the surface has a darker appearance.  The metallic sheen might disappear.  The standard pictures in VIS-4 do not provide illustrations of pressure-washed surfaces.
In the first two pictures, the substrate was pressure washed (ca 1000 psi) to remove the loose dust so that the substrate would meet a “light” flash rust requirement..
The substrate dried in a few minutes.  Flat surface can take longer to dry.

INSPECT the AREA AFTER PRESSURE WASHING.
Note that the loose dust is removed.
However, the stains on the right have remained.
The inspector, contractor, paint manufacturers, and owners (all the responsible parties in a coatings project) should note streaked areas and obvious runs. 

In this example, the source of the water that created the original flash rust came from a hole in the ship that most likely had salts or oil and greases.  Special attention should be given to those areas. Look to the project specifications as to what other inspections might be required.

At the right, notice that some areas are not washed, some have dried, and some are still drying.

Here are more pictures showing the same type of situation, where some areas are not yet washed, some are dry, and some are still drying.

Close up of area on right in picture above.

To Repeat: the inspector, contractor, paint manufacturers, and owners (all the responsible parties in a coatings project) should note streaked areas and obvious runs. 

In this example, the source of the water that created the original flash rust came from a hole in the ship that most likely had salts or oil and greases.  Special attention should be given to those areas. Look to the project specifications as to what other inspections might be required.
All the defects can be seen.  There are stains, but NO loose rust dust.

All the defects can be seen.  There are stains, but NO loose rust dust.

This is the result of the Brush Wipe Test on Heavily Stained & Heavy Flash Rust Area

Before Pressure Washing

Before Pressure Washing.

After Pressure Washing. Hand wiping test.

After Pressure washing. Brust test.

A direct comparison between hand wipe and brush test on pressure washed moderate flash rust indicates no differences.

 None
 Light
 Moderate
 Heavy
Adopt the method with which you feel most comfortable and that is portable to different projects and sites.

Examples of LFR on Swatch, wipe, and Brush

Example of MFR on swatch and brush wipe.

HFR on Swatch

HFR on Brush Wipe

HFR with Swatch, Brush, and Wipe

 Brushing flash rust is quick, simple, and very reproducible.
 Adopt a standard brush and standard cloth.
 Be consistent with one swipe and in the same direction and duration.
 Practice brush strokes with even pressure
 Keep the contact area consistent.
 Cloth can be cut at the area of color transfer and placed in permanent file or scanned for color.

Heavy Flash Rust formed from water coming from holes.
Different section where Light, moderate, and heavy flash rust had formed in close proximity.

Left to right, Light, Moderate, Heavy. Brush tests taken at the same time from three different areas.

Some color is transferred from light flash rust.

This view has the sun Illuminating the surface.  Substrate appears darker as it is in shadow. Inspection is biased by lighting angle.

This method was developed by Todd Pacific Shipyard. These photos are courtesy of Todd Pacific.
 Sweep the surface with a Cloth wrapped around a brush
 Standard cloth and standard brush.
 Wrap cloth around a paint brush. Swipe the cloth across the surface.
 Define the amount of pressure
• Brush as if painting a door
 Define the amount of contact- single stroke (for example 4 inches (10 cm))
 Define direction- pull down, pull up, or single stroke sideways
 BE CONSISTENT with length of path and type of cloth!
Be consistent with the amount of surface you are wiping
Cheese cloth is in some of the photos. Dr. Frenzel found it was difficult to see color transfer; she preferred woven cotton for consistency.
Be consistent with the type of brush and the pressure.

Get a standard brush.

Get a standard cloth and wrap around the brush.

Brush once as if painting a door.

Light flash rust, little color.