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.

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.

 Easy to prepare the swatches.
 Keeps a constant light pressure.
 Gives a clear distinction between light, moderate, and heavy.
 The color transfers to only the cloth that is in contact with the surface. It can be difficult to interpret the various spots of color.

Comparison of two types of clothes. Cloth can make a difference. Be consistent in your selection of cloth.

Swatch Test with Two different cloths in another field case of “Heavy” Flash Rust.
In this comparison, we got two different results.

 Advantage of holding cloth in hand and wiping. It is easy.
 Disadvantage – it is difficult to maintain an even pressure and keep the cloth on the surface.

This side took forty minutes to dry.

THis side took only six minutes to dry.

 

Note the formation of the dark, black rust under the light brown rust. There is a lot loose rust obscuring the surface, but no rust scale has formed.

These colors are easily transferred to the hand wipes.

 Make a bundle of cloth in your hand.
 Swipe the dry cloth across the surface.
 Make one swipe, up or down or sideways with the cloth touching the surface.
 Try to avoid pressing the fingers against the surface.

The following four pictures are examples of hand held wips and light flash rust.

Close up of two Light Flash Rust cloths.

In the two pictures above, the top one shows transference where the fingertips met the surface. There might be some color, but not much.