Introduction
Swarf, also known as metal ﬁlings or rust spotting, refers to steel debris created from cutting or piercing operations when using friction saws, abrasive discs, drills etc., on steel rooﬁng and siding products. This debris in addition to other discarded steel objects such as rivet shanks, nails, screws and nuts, which may come in contact with coated products (i.e. pre-painted steel) are the subject of this bulletin.

Swarf particles, if left on the surface, will corrode and cause rust stains which will detract from the ﬁnished appearance of a project. These stains are often mistaken for early deterioration of the rooﬁng or siding itself.

Fresh swarf stains are typically small red-brown colored areas with a central dark spot (remnants of the steel particle). The surface will feel rough, and the particle may be dislodged with a ﬁngernail. An older swarf stain will have a smooth, redbrown stain, the original steel particle having corroded away. Prevention of such staining is the responsibility of the installer and it is strongly suggested that the recommendations contained in this
bulletin be followed.

Metal debris will come in contact with coated steel sheet products in three ways:

Loose particles left after cutting, drilling and riveting operations.

Hot metal ﬁlings from disc cutting or drilling operations which may adhere to the ﬁnished surface.

Loose particles which may be ground in underfoot or become embedded in the surface ﬁlm of pre-painted products under pressure from adjacent equipment or materials.

Prevention

Cutting:
Use of a cold cutting saw with an appropriate tungsten blade is the best way to cut sheets on site. This method generates larger, cooler particles than abrasive discs. Where possible, cutting should be minimized by using factory supplied cut-to-length sheets. Sheets cut on site should, where practical, be cut on the ground, with the exterior color ﬁnish of pre-painted sheet facing down. Care should be taken to ensure hot ﬁlings do not come into contact with nearby pre-paint steel sheets. Do not cut over the top of other coated products, where debris may fall onto other sheets. Where cutting must be carried out near sheets already installed, the area around the cut must be covered and the stream of hot particles directed away from completed work. Field cut edges should be concealed under ridge caps or gable flashings whenever possible. See ASC Building Products' Technical Bulletin #6 Field Cutting Metal Panels for additional details.

Drilling:
The area around the hole should be covered to shield the product from hot metal ﬁlings. Avoid pre-drilling fastener holes while panels are stacked or bundled. If pre-drilling is necessary carefully clean each panel immediately.

Installation:
Smooth soled shoes should be worn when working on a roof; avoid the ribbed type which will carry metal ﬁlings and other objects.

Clean Up:
Metal debris/ﬁlings should be swept or hosed from the job progressively and certainly at the end of each day. This action will remove loose particles. Maximum care should be taken when attempting to detach ﬁlings which have become stuck; this can be
done, but no action which is likely to remove paint or metal coatings should be attempted. Any damage to these coatings will lead to reduced life of the material.

When sweeping or hosing into a gutter, clean out the gutter before leaving the job to prevent premature corrosion. On completion of the job give a ﬁnal wash or sweep down. For critical applications, inspection of the job should be made after two weeks when rain or condensation will have caused any remaining ﬁlings or debris to rust and will highlight affected areas.

Note: Many staining problems arise not from installers, but from other contractors working in the vicinity. Architects and builders need to be aware of this possibility and warn contractors accordingly.

Effect on Performance:
The effect of staining itself on ASC Buildind Products' preﬁnished products is generally aesthetic and may not be detrimental to the performance of the product. The product life will be severely affected where attached metal particles have penetrated the pre-painted ﬁlm and are in contact with the protective metallic coating, although this only occurs in severe cases. This is because on pre-painted surfaces red oxides of iron are normally inert substances and do not attack the ﬁnish; the stain is merely absorbed by the ﬁnish. Red oxides of iron are insoluble in water and the stain will take considerable time to weather away.

On metallic coatings, concentrated corrosion can occur over a small area as the zinc in the coating sacriﬁces itself to prevent oxidation of both the debris and, if allowed to continue, exposed areas of the steel base.

Repair of ZINCALUME Steel Sheet:
Brush the surface with a stiff bristle (not metallic wire) brush to dislodge particles which must then be completely removed. Wire brushing will mar the appearance of the sheet if brushing is not followed by painting. If the coating is severely damaged by corrosion, the area should be painted. Please contact Steelscape to discuss the correct coating to repair the damaged area.

Salem, OR Spokane, WA

Phone: 800-272-7023
Phone: 800-776-8771

Fax: 800-404-7443
Fax: 800-767-1346

For most current versions of literature please visit

www.ascbp.com

Repair of ZINCALUME Steel Sheet:

Mild Staining:
A household cream cleanser, used according to directions, will remove most mild staining from metal debris (one cup of mild, common detergent which contain less than 0.5% phosphate, dissolved in warm water are usually effective). Avoid the use of aggressive cleaners such as TSP.

Severe Staining:

Clean the surface by washing with a non-ionic industrial or household detergent and water in proportions as
recommended by the detergent manufacturer. Wash well with clean water.

Remove the corrosion product by using a stiff nylon brush and washing off completely. More heavily affected areas may need a light rub with a Scotch-Brite guard pad (not steel wool).

Abrasive papers should only be used if repainting is to be carried out. Great care must be taken not to cause damage to the paint ﬁlm.

Hose down the affected area completely after treatment.

This treatment will normally leave only very mild stains.

Very Severe or Extensive Staining:
In these cases, if aesthetics is important, either replacement or ﬁeld painting may be the most appropriate option. Field applied paints will weather faster than factory applied, therefore the entire visible area should be repainted.

Note: The above repair actions will not fully restore the product to its original state. It is critical to ensure that swarf is avoided.

Heavy swarf staining on pre-painted steel.

Moderate swarf staining on ZINCALUME Plus.

Salem, OR Spokane, WA

Phone: 800-272-7023
Phone: 800-776-8771

Fax: 800-404-7443
Fax: 800-767-1346

For most current versions of literature please visit

www.ascbp.com