B08_Attachment_6_-_SAFR_Process_and_Material_Specificaitons_0001.pdf

ATTACHMENT 6

SAFR MATERIAL AND PROCESS

SPECIFICATIONS

Appendix A – Process Specifications

The Contractor must provide proposed changes to the standard to the COR for the process intended prior to beginning any work item. The COR shall approve or deny any proposed change in standard.

SEA TRIALS

ISO 19019:2005

WOOD PRESERVATION TREATMENT

American Wood Protection Association Book of Standards (AWPA) 2016 U1-16 Standard, SBX P25-8 (Replaces former P5 and C31-95) – Pressure Treatment with inorganic boron

The Contractor must strictly adhere to the following preservation treatment procedures on all wooden components, (Laminated masts shall have a separate and different preservation procedure). All wood surfaces that have been cut, sanded, penetrated or perforated by the Contractor must have the interior surfaces of any hole, perforation or the area sanded or area cut swabbed twice (2x) with a fifteen percent, (15%), solution of Tim-bor wood preservative or COR approved chemical equivalent and allowed to dry prior to other coatings and installation.

Timbers, Beams, Sheathing, Trim and Decking:

All Douglas Fir to be used shall be Hi-Bor pressure borate treated per Hawaii construction standards with clear borate treatment, then sealed inside a waterproof barrier material for shipment per AWPA SBX P25 standards.

As soon as possible after the tree is cut the log should be treated at both ends and at all bark scars with a 5-10% solution of Tim-bor .

Prior to milling:

After the bark is removed, apply a 15% aqueous solution of Tim-bor to all wood surfaces by brush or spray until wood surface is thoroughly wet, at a rate of approximately 5 gallons per 1000 square feet of surface area. If shaping will not begin within one week, the entire log should be wrapped and sealed until milling begins.

Following milling:

Immediately following all shaping procedures apply 15% aqueous solution of Tim-bor to all wood surfaces by brush or spray until surface is thoroughly wet, at a rate of approximately 5 gallons per 1000 square feet of wood surface area. Before surfaces are allowed to dry, wood is to be thoroughly sealed inside a waterproof barrier material such as plastic wrap, and delivered to Hi-Bor clear borate pressure treatment facility as soon as possible.

Inorganic Boron (Borax–Boric Acid) Borate preservatives are readily soluble in water and highly leachable and should be used only above ground where the wood is protected from wetting. When used above ground and protected from wetting, this preservative is very effective against decay, termites, beetles, and carpenter ants. Inorganic boron (SBX) is listed in AWPA standards for protected applications such as framing lumber. The solid or treating solution for borate preservatives (borates) should be greater than 98% pure, on an anhydrous basis (AWPA P5). Acceptable borate compounds are sodium octaborate, sodium tetraborate, sodium pentaborate, and boric acid. These compounds are derived from the mineral sodium borate, which is the same material used in laundry additives.

Preservative source:

Tim-bor source and application information can be obtained from U.S. Borax Inc, or online.

Precautions:

Disodium octaborate tetrahydrate (Tim-bor) presents little or no hazard to humans and has low acute oral and dermal toxicities. However, read and follow instructions and precautionary statements on label and MSDS.

Preservation solution preparation:

To prepare solution, hot water should be added to the mixing tank to about 80% of the final volume of solution required. While agitating, add 1.5 pounds of Tim-bor for each gallon of treating solution. Use of warm or hot water (120-150 degrees F) will aid in dissolving the product.

PAINT

ASTM D6386-10 Standard Practice for Preparation of Zinc (Hot-Dip Galvanized) Coated Iron and Steel Product and Hardware Surfaces for Painting

ASTM D3274-09(2021) Standard Test Method for Evaluating Degree of Surface Disfigurement of Paint Films by Fungal or Algal Growth, or Soil and Dirt Accumulation

All requirements and recommendations of the Paint Manufacturers Representative or Product Literature for the paint utilized. Paint to be applied to meet the mils dry film thickness (MDFT) identified by the paint manufacturer or the paint manufacturer’s representative.

Wooden Components

Surfaces to be painted shall be clean and free of grease, dirt, dust and other foreign matter before application of paint or surface treatments. After cleaning, surfaces shall exhibit a surface disfigurement rating of 7 or greater when evaluated in accordance with ASTM D3274. Dirt and surface contaminants shall be cleaned by brush with solutions of water and detergent or trisodium phosphate, then rinsed clean with water and let dry. Surfaces on which mildew or other microbiological growth is present shall be cleaned with a detergent solution containing household bleach. Oil and grease shall be removed with clean cloths and cleaning solvents prior to mechanical cleaning. Cleaning solvents shall be of low toxicity with a flashpoint in excess of 38 degrees C (100 degrees F). Cleaning shall be programmed so that dust and other contaminants will not fall on newly prepared or newly painted surfaces.

Surface Preparation:

Previously painted surfaces shall have all loose coatings removed to either bare wood or to a point where the paint is thoroughly bonded to the wood. Paint edges shall not be able to be lifted with a knife or finger nail.

Edges where old paint meets exposed wood or lower coatings of paint shall be sanded and faired presenting a smooth transition from bare wood/previously coated surfaces to topmost prepared coating.

Loose, cracked, or missing bungs shall be replaced prior to application of coatings.

Carefully remove damaged or loose bungs without damage to surrounding wood.

Prepare and coat metal fastener per below (Metal Surfaces).

Bungs shall be same material as the parent material with the grain of the bung oriented same as parent material and glued in place with two (2) part epoxy glue.

Between applications of any coatings, sand material smooth.

If wood material was previously oiled, prepare surface and apply Owatrol or Textrol according to the manufacturer’s recommendations.

New bare wood shall receive two (2) coats clear wood sealer (Z-Spar S-120 Wood

Sealer or COR approved equal).

All wooden surfaces shall receive one (1) marine alkyd primer coat at (Z-Spar 105

Undercoat or COR approved equal). Prime coat may be tinted with topcoat paint.

Thinned topcoat paint is not approved as a primer.

Metal Components

All metal components that are to be used (new or old) shall be sand blasted to an SSPC-SP6 specification and then inspected for cracks, signs of fatigue or level of deterioration. The inspection will inform the next steps, whether they are galvanizing and paint or repair or replacement.

Surface Preparation:

SSPC-SP6 Blast Cleaning Hot dipped galvanized as specified above.

All surfaces shall be coated with one (1) coat anti-corrosive paint at 5mils dry per coat.

(Intershield 300V or COR approved equal)

Metal Surfaces

Metal surfaces specified to be cleaned to SSPC-SP3 shall have a 2.5% mixture of tannic acid1 applied following mechanical preparation and solvent wipe. Following application and cure of tannic acid, apply one (1) clear coat epoxy encapsulant (Interbond 600 @ 1 MDFT or COR approved equal), followed by two (2) coats anti-corrosive epoxy paint at 5 MDFT each (Intershield 300V or COR approved equal) and top coated as specified.

Metal Component Vinyl-Ester Coatings

PREPARATIONS AND COATING OF HULL

REQUIREMENTS: The Contractor shall provide the labor, material and equipment to sandblast, clean, and coat areas designated below with a three-part vinyl-ester resin coating system. The coating system must protect the hull from cavitation, abrasion and corrosion. To ensure the coating system is adequate for this application, the coating system must meet the following mechanical requirements:

Test Description Minimum Value Scale Test Method

Adhesive Strength on steel 4000 psi Direct pull

1 Tannic Acid Coating for Rusted Iron Artifacts, formerly published under the title Tannic Acid Treatment – Canadian Conservation Institute (CCI) Notes 9_5 - Canada

Tensile Strength 5000 psi ASTM D638-08 Compressive Strength 20000 psi AMTM D695-8 Flexural Strength 12000 psi ASTM D790-07 Hardness 85 Shore D D2240-05 Izod Impact Resistance 3.5 ft-lb /in D256-06a Dielectric Strength 15000 volts/ mm D149-09 Dielectric Constant 3 k D150-98 Taber Abrasion test CS-10 wheel

(maximum) 0.05 mg loss/ cycle 1000 cycles 1000 g load

The coating System shall also meet or exceed the following certifications or approvals:

Class “A” flame spread index and smoke Developed index. Per ASTM E-84-11a Flash point of at least 27 C per ASTM D3278 Have A VOC content below 280 g/L per ASTM D-2369 Tested and passed IMO Performance Standard for Protective Coatings per IMO

Resolution MSC 215 (82) :2006 The coating system shall be certified by an independent testing laboratory to be NSF – 61 compliant for potable water and must not contain any of the following heavy metals or substances that could harm humans or marine life: Antimony, Arsenic, Beryllium, Cadmium, Chromium, Cobalt, Copper, Fluoride, Lead, Mercury, Molybdenum, Selenium, Silver, Tantalum, Thallium, Tungsten or Vaadium.

All of these material properties shall be verified by providing test result, completed by an independent testing laboratory, to the COR.

The coating system must have previous history of protecting hulls from cavitation, abrasion and corrosion for a minimum period of 10 years, or as long as the proposed warrantee. The previous history will be verified by references to be provided to the COR.

A. All coatings shall be applied under the guidance of the coating system manufacturer’s technical representative.

1) The Contractor shall arrange an inspection by the coating system manufacturer’s technical representative and the COR prior to the base coat application, reinforcement coat application and top coat application.

2) No application of coatings is to be made until the prepared surfaces are approved by the COR under the guidance of the coating system manufacturer’s technical representative.

3) Areas found to contain runs, overspray, inadequate film thickness, roughness, impregnated dust or grit, or any other film or surface preparation irregularities are to be repaired or re-coated as directed.

B. Sand Blast the test area of the hull surfaces to white metal (SP-10). The surface profile of all sand blasted metal shall have a minimum surface profile of three (3) mils. Before the application of coating system, the substrate must be clean (have a minimum dust removal rating of 1) and be free of salts (less than 50 mg per square meter of total soluble salts) and other chemical impurities and be completely dry. The guidelines referenced shall be followed including the Contractor’s process for lead abatement procedures.

C. The Contractor shall apply coatings to hull test area as follows:

1) One (1) coat of base coat. Base coat is used as a primer over bare substrate. The base coat shall be applied by brush or spray. On porous surfaces, base coat shall be rubbed into the freshly prepared surface to insure there are no voids in the coating and that the substrate is 100% coated. Base coat shall be applied at a minimum of 15 MDFT.

2) One (1) coat of reinforcement coat. Reinforcement coat is used to structurally fill pits or blemishes, as a structural fairing compound to cover over welds or other blemishes to make them more hydrodynamic or it can be brushed or trawled over entire areas as extremely durable high build coat. The reinforcement coat SHALL NOT be sprayed, it must be applied with a brush or trawl. Contractor shall brush or trawl on one layer of reinforcement coat directly onto areas that have previously been coated with base coat. For filling pits, screed pits level with surrounding areas using a plastic spatula. Deep pits may require multiple coats to fill completely. Sand smooth any imperfections, runs or drips prior to applying top coat. There is no required MDFT for the reinforcement coat.

3) One (1) coat of topcoat. Topcoat is used as a finish coat over areas that have been previously coated with either base coat or reinforcement coat. The topcoat shall be applied by brush or spray. Topcoat shall be applied at a minimum of 15 MDFT.

D. Application instructions of the coating system manufacturer and its represen-tatives shall be strictly adhered to.

E. Coatings must be completely mixed per coating system manufacturer instructions.

F. Coatings shall only be applied when all surfaces are at least 3-degrees Celsius above dew point.

G. The coating system manufacturer's recommendations for applying, drying and re-coating times are to be strictly adhered to.

H. Remove all protective coverings installed in this section.

TESTING/INSPECTION/REPORT:

A. Mil Dry Film Thickness (MDFT) measured after each coat has been applied.

B. Inspect dryness prior to next coat.

C. Inspect all protective coverings after installation and removal.

Topcoats – Wood and Metal

All wood surfaces shall be sanded to receive two (2) semi-gloss marine alkyd coatings at

MDFT recommended by the Paint Manufacturer’s Representative or product literature.

All metal surfaces shall have two (2) part semi-gloss epoxy paint applied within the time frame specified by the paint manufacturer’s representative to allow proper chemical bonding to the prime coats.

First topcoat shall dry sufficiently to reach minimum hardness specified by the manufacturer before sanding or overcoating.

Mil Film Dry Thickness (MDFT) shall be measured after each coating.

First topcoat shall be sanded, cleaned and wiped with denatured alcohol (or COR approved equal) to accept second topcoat.

Areas found to contain runs, overspray, inadequate film thickness, roughness, impregnated dust or grit, or any other film or surface preparation irregularities are to be repaired or re-coated as directed by the COR at no additional cost to the government.

Colors shall be consistent throughout the project and approved by the COR.

CAULKING

Reference: NAVSEA_009-037_FY26_Woodwork

All seams are considered properly caulked when they contain a minimum of two strands of cotton followed by at least one strand of marine oakum. Additional stands of oakum shall be used where necessary to bring the caulking to a consistent depth of ½” to the top of the seam (or a depth equal to the caulking seam width).

Install new spun cotton and marine oakum in the reefed out caulking seams. Seams shall be clean and dry before caulking is installed. Caulked seams require at least two strands of treated caulking cotton.

Drive the strands of caulking cotton into the bottom of the seams, prior to installing marine oakum.

Install strands of marine oakum in the caulking seam to bring the caulking to a consistent proper depth.

Butt seams shall be caulked ahead of adjoining longitudinal. The ends of sound caulking and new caulking shall be drawn out and tapered so as to marry in a continuous bulk.

Horse the caulking soundly into the caulking seam using beetles, horsing irons, caulking irons and caulking mallets. Great care shall be exercised to prevent blow-out through the bottom of the caulking seam and to ensure a consistent depth of caulking 3/8” depth from the top of the seam.

Deck Seams shall be filled with Jeffries No2 Marine Glue. The heat of the glue must be monitored to assure that is not so hot as to bubble and aerate the glue as it hardens.

Excess glue shall be removed with scrapers to provide a smooth surface and clean deck area after the pitch has been allowed to set up. Bubbles or voids found after the pitch has set shall be remelted and smoothed with an iron.

Hull Plank Seams (above the waterline) shall be payed with Interlux white above water seam comound (or COR approved equal).

Hull Plank Seams (below the waterline) shall be payed with pure Portland cement, troweled smooth with the adjacent plank surfaces.

Testing Water test seam caulking to ensure all seams are watertight.

Bungs which, due to slope of grain, split off below the plank surface are to be replaced.

Material Caulking Cotton o FED SPEC: A-69515, T-C-30 Jefferies No.2 Marine Glue Hemp Oakum, Norwegian (spun SPUNNET VIKING or equivalent) o FED SPEC: T-O-56A Oakum Pure Portland Cement Interlux above water seam compound (white)

RIVETING

Reference:

Video Library - Historic Bridge Restoration Chapter V Rivets RF Evolution of historical riveted connections: joining typologies, installation techniques and calculation methods. Structural Repairs and Maintenance of Heritage Architecture XII

WELDING

ASTM 488/A488M-99 Practice for Steel Castings, Welding, Qualifications of Procedures and Personnel All welds shall be full penetration butt welds.

All welds shall be sufficient for the intended use of the component and shall be identified in the component drawings from CLIN 1.2.1

FORGING

ASTM A388/A388M-95 Practice for Ultrasonic Examination of Heavy Steel Forgings ASTM A668/A668M-13e1 Standard specification for steel forgings, Carbon and Alloy – General Industrial ASTM A711/A711M-07 Standard Specification for Steel Forging Stock ASTM A788/A788M-13 Standard specification for steel forgings ASTM A769-A769M-05(2010) Standard Specification for Carbon and High-Strength Electric Resistance Forge-Welded Steel Structural Shapes ASTM A952/A952M-98 Specification for Forged Grade 80 and Grade 100 Steel Lifting Components and Welded Attachment Links ASME Y14.8 Castings, Forgings and Molded Parts ASME B18.15-1985 Forged Eyebolts

CASTING

ASTM A27/A27M-95 Specification for Steel Castings, Carbon, for General Application ASTM A47/A47M-99 Specification for Ferritic Malleable Iron Castings ASTM A148/A148M-93b Specification for Steel Castings, High Strength, for Structural Purposes ASTM A247-67 Test Method for Evaluating Microstructure of Graphite in Iron Castings ASTM A327-91 Test Methods for Impact Testing Cast Irons ASTM A532/A532M-93a Specification for Abrasion-Resistant Cast Irons ASTM A644-98 Terminology Relating to Iron Castings ASTM A802/A802M-95 Practice for Steel Castings, Surface Acceptance Standards, Visual Examination ASTM A834-95 Specification for Common Requirements for Iron Castings for General Industrial Use ASME Y14.8 Castings, Forgings and Molded Parts

METAL PREPARATION AND SAND BLASTING

NACE No. 3/SSPC-SP 6 Commercial Blasts Cleaning SSPC-SP3 Power Tool Cleaning https://historicbridgerestoration.com/video-library/

GALVANIZING

ASTM A123/A123M-13 Standard Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products ASTM A153 / A153M Standard Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware ASTM A385/A385M-11 Standard for high quality zinc coatings (hot dip)

Canada.ca

Culture, history and sport

History and heritage

Museology and conservation

Preservation and conservation

Conservation tools and resources

Conservation and preservation publications

Canadian Conservation Institute (CCI) Notes

Tannic Acid Coating for Rusted Iron Artifacts, formerly published under the title Tannic Acid Treatment – Canadian Conservation Institute (CCI) Notes 9/5

CCI (Canadian Conservation Institute) Note 9/5 is part of CCI (Canadian Conservation Institute) Notes Series 9 (Metals) Caution:

This Note discusses actions that will physically affect the object, and/or procedures that involve the use of chemicals. Exercise caution, and seek qualified assistance if in doubt.

Introduction

Iron objects are often covered with a layer of corrosion, which can vary from a light rust film to heavy, disfiguring scale. Corrosion is undesirable when it detracts from an object's appearance and usefulness for display. Also, because iron rarely corrodes in an even, regular manner, the corrosion layers are not as protective as those formed on other metals and they allow https://www.canada.ca/en.html https://www.canada.ca/en/services/culture.html https://www.canada.ca/en/services/culture/history-heritage.html https://www.canada.ca/en/services/culture/history-heritage/museology-conservation.html https://www.canada.ca/en/services/culture/history-heritage/museology-conservation/preservation-conservation.html https://www.canada.ca/en/services/culture/history-heritage/museology-conservation/preservation-conservation/tools-resources.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes.html https://www.canada.ca/en.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes.html water vapour and oxygen to penetrate to the iron surface and react with the underlying metal (consult CCI (Canadian Conservation Institute) Notes 9/1 Recognizing Active Corrosion).

Tannic acid is a complex organic acid found in plants. Different types of tannic acid are usually identified by the species of plant from which they come. When applied to iron, tannic acid reacts with the iron ions to form ferric tannate, a somewhat porous blue-black film whose degree of protection can be controlled to some extent by the method of application. It produces a uniform finish that enhances the appearance of an object (for more information on the effects of tannic treatment on iron, consult Selwyn 2004 ).

Tannic acid should not be used on objects originally intended to be brightly finished or painted. As tannic acid produces a blue-black surface, it is suitable for wrought and cast iron, on which such a finish is appropriate.

It is important to remember that the application of tannic acid will not eliminate the need for a museum environment, nor will it remove damaging soluble salts from actively corroding objects (consult CCI (Canadian Conservation Institute) Notes 9/6 Care and Cleaning of Iron).

Preparing the Iron

Before applying tannic acid to rusty iron, the surfaces should be free of dirt, accretions, oils and grease (consult CCI (Canadian Conservation Institute) Notes 9/6 Care and Cleaning of Iron). Composite objects, i.e. objects composed of different materials, should ideally be dismantled. If this cannot be done, ensure that the tannic acid does not touch any material other than the iron. Tannic acid can permanently stain materials such as wood, paper, wool, silk, leather, bone, horn and ivory.

It is not necessary or desirable to remove light rust films or heavy corrosion before applying tannic acid.

https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/recognizing-active-corrosion.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/recognizing-active-corrosion.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/recognizing-active-corrosion.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/recognizing-active-corrosion.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/care-iron.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/care-iron.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/care-iron.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/care-iron.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/care-iron.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/care-iron.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/care-iron.html

Preparing the Acid Solution

Tannic acid is a light, fluffy powder. Its colour varies from brown to golden brown, depending on the grade and the manufacturer. Like many natural plant products, tannic acid is a mixture of polymers, which means that a uniform formula for tannic acid does not exist and that the composition can vary among available brands.

As with any concentrated chemical, tannic acid poses a potential health hazard. Be careful not to inhale the powder or bring the acid in contact with skin. A dust mask should be worn when weighing and mixing the dry powder. For convenience, it is recommended that a 10% (w/v (weight per volume)) solution of tannic acid be prepared and portions used or diluted as needed. Keep the 10% (w/v (weight per volume)) solution refrigerated to reduce the chance of it going mouldy.

Recipe for one litre of 10% solution of tannic acid:

100 g (grams) tannic acid 900 mL (millilitres) deionized or distilled water 50 mL (millilitres) ethanol approximately 2 mL (millilitres) dilute phosphoric acid (H PO )

Notes on the ingredients:

Tannic acid is very light, so a 100 g (grams) measure is bulky. A mixing vessel holding at least 1.5–2.0 L (litres) is therefore required.

Use deionized or distilled water; tap water may contain chloride ions and other dissolved salts that encourage iron corrosion.

Ethanol acts as a wetting agent that enhances the flow of the solution into porous corrosion layers and into all fissures on a corroded iron surface.

Phosphoric acid lowers the pH (potential of Hydrogen) of the acid solution, and increases the amount of dissolved iron ions available for reaction with tannic acid. It is not necessary to be concerned about acid residues remaining on the iron, since phosphoric acid will react with iron ions to form ferric phosphate, which protects iron. Very little acid is

3 4 introduced from this method, and there is no danger of excess amounts crystallizing on the surface.

Equipment:

a balance a mixing container (glass), at least 1.5 L (litre) capacity, that can be heated a scoop and stirring spoon or rod an eye dropper pH (potential of Hydrogen) papers a measuring device marked in millilitres (mL) (e.g. a graduated cylinder) a stirrer/hot plate personal protective equipment including gloves, a dust mask, eye protection and a lab coat or full apron

Mixing the solution

Tannic acid stains, so protective clothing (gloves and a lab coat or full apron) are advised. Safety glasses or goggles must be worn. If eyeglasses make it difficult or impossible to wear normal safety glasses, a full face shield should be used. Tannic acid is a fine powder and, during preparation, a dust mask should be worn to avoid inhaling it.

Measure and mix 800 mL (millilitres) deionized or distilled water and 50 mL (millilitres) ethanol in a glass container. Plastic containers should not be used because they cannot be heated.

Weigh out the 100 g (grams) of tannic acid. If you do not have a balance, you may be able to borrow one from a school science lab.

Gradually add the tannic acid to the water/ethanol solution, stirring constantly. To accelerate the process, gently heat the solution on the hot plate. When the tannic acid has dissolved, add enough deionized or distilled water (approximately another 100 mL (millilitres)) to make a total volume of 1 L (litre).

Test the pH (potential of Hydrogen) of the solution using pH (potential of Hydrogen) papers. If it is greater than 2.4, it will be necessary to lower the pH (potential of Hydrogen) with dilute phosphoric acid.

Prepare a dilute phosphoric acid solution by pouring 9 mL (millilitres) distilled or deionized water into a glass container and adding 1 mL (millilitre) concentrated phosphoric acid, usually sold in an 85% (w/w (mass by mass)) concentration. Always add acid to water, rather than vice versa, to avoid a violent reaction.

With the aid of a dropper, add a few drops of the dilute phosphoric acid to the tannic acid solution, stirring continuously. After adding about 10 drops, test the pH (potential of Hydrogen) again. Continue the drop-wise addition of the acid until the pH (potential of Hydrogen) decreases to between 2.2 and 2.4. This may require about 50 drops (2 mL (millilitres)) of the dilute phosphoric acid, depending on the initial pH (potential of Hydrogen) of the tannic acid solution (consult Figure 1 for pH (potential of Hydrogen) range).

Unused dilute phosphoric acid can be washed down the drain with running water.

Figure 1. Schematic diagram showing pH (potential of Hydrogen) 1 (acidic) through pH (potential of Hydrogen) 7 (neutral) to pH (potential of

Hydrogen) 14 (alkaline). Indicated is the pH (potential of Hydrogen) range for tannic acid solution, 2.2–2.4, which is acidic.

Dilution of Tannic Acid Stock

To achieve an even coating of ferric tannate, it is best to apply several coats of a dilute solution of tannic acid rather than one concentrated coat. Ten percent tannic acid, as prepared above, is too concentrated to produce a good result. For most purposes, it should be diluted to between 2% (w/v (weight per volume)) and 3% (w/v (weight per volume)).

A simple method of dilution is to mix the 10% (w/v (weight per volume)) solution 50/50 with deionized water, thereby yielding a 5% (w/v (weight per volume)) solution. If desired, this 5% (w/v (weight per volume)) solution can then be diluted 50/50 again with deionized water, yielding a 2.5% (w/v (weight per volume)) solution.

Remember to test the pH (potential of Hydrogen) of the diluted solution and, if necessary, add a few drops of dilute phosphoric acid until it is between 2.2 and 2.4.

Applying the Tannic Acid

Prepare a working space, preferably a table. Empty the table and cover it with polyethylene sheeting taped down at the edges. Two stiff bristle brushes, such as toothbrushes, are required: one to apply the acid and one to brush the object after the acid has dried. Because this procedure can be messy, ensure that the acid will not splatter surfaces that it could stain (e.g.

wood, clothing). In good weather, the procedure can be performed outdoors. Protective clothing and safety glasses are advised.

Transfer a small amount of 2.5% (w/v (weight per volume)) solution into a suitable container, such as a small Pyrex beaker. Heat the solution to about 50°C and brush it onto the object's surface. When this solution becomes black, discard it and start again with fresh solution.

Continue brushing as the solution dries in order to distribute the acid evenly and to introduce oxygen. This will produce an even colour.

Colour change will occur quickly, usually beginning in pitted areas. These areas resist further reaction as they become coated with an even, coherent film of ferric tannate. The tannic acid will then begin to react with less corroded areas. The presence of phosphoric acid helps establish an even reaction over the surface. Once the first coat has dried, the surface of the iron should be brushed with a stiff, dry brush to remove flaky areas of ferric tannate. Another coat of warm tannic acid should then be applied. Continue brushing as the acid dries.

Repeat these steps until a coating of the desired thickness and colour is achieved.

When dealing with case-hardened objects and steels, such as cutting tools, the tannic acid/iron reaction may be different around the working edges.

Also, a different appearance in the ferric tannate should be expected at welds or joins. Heavy corrosion layers on objects will take longer to react and require more coats than will light rust or bare metal.

Some practice may be necessary to become familiar with the ferric tannate film and how to control its formation. By increasing the concentration of tannic acid from 2.5% (w/v (weight per volume)) to 5% (w/v (weight per volume)), a much darker, thicker film can be achieved. Excess ferric tannate will merely flake off the surface.

Care of Objects Treated with Tannic Acid

Ferric tannate films are not vapour barriers. They will delay or retard corrosion by forming a film over iron, but this effect will not last indefinitely.

The life of the film can be extended by:

storing the object in stable relative humidity (RH), preferably around 50% (consult CCI (Canadian Conservation Institute) Notes 9/6 Care and Cleaning of Iron) wearing gloves when handling the object protecting the surface from dust and abrasion https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/care-iron.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/care-iron.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/care-iron.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/care-iron.html

Ferric tannate sometimes rubs off onto other materials. Surfaces treated with tannic acid should not be allowed to contact absorbent objects that stain easily, such as paper, textiles, leather, bone and wood.

If spots of rust begin to appear through the ferric tannate film, check the RH (Relative humidity) and carefully examine the object to ensure that the spots are not a result of chloride contamination (consult CCI (Canadian Conservation Institute) Notes 9/6 Care and Cleaning of Iron). If recurrence of rust appears to be due to failure of the ferric tannate film, the object should be re-treated with tannic acid. It is not necessary to remove the original ferric tannate layer.

It is not necessary or advisable to put a protective finish, such as a wax, oil or lacquer, over a surface treated with tannic acid when the object is kept indoors under museum environmental conditions. Protective coatings like waxes and lacquers do not stop the transmission of water vapour and oxygen, only reduce them. When applied to porous corrosion layers, the coatings may be very difficult to remove if the object begins to actively corrode. A tannic acid coating will not protect against corrosion in an outdoor environment and will quickly degrade (Binnie et al. (and others) 1995 ).

For further information on storage of metal objects, consult CCI (Canadian Conservation Institute) Notes 9/2 Storage of Metals.

Suppliers

Tannic acid:

chemical suppliers

Phosphoric acid:

drugstores, some school chemistry departments or chemical suppliers

Ethanol:

school chemistry departments or chemical suppliers

Brushes:

art supply or hardware stores https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/care-iron.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/care-iron.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/care-iron.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/care-iron.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/storage-metals.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/storage-metals.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/storage-metals.html https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/storage-metals.html

Distilled water:

drugstores or hardware stores pH (potential of Hydrogen) paper:

chemical suppliers

Bibliography

Binnie, N.E., L. Selwyn, C. Schlichting and D.A. Rennie-Bisaillion. "Corrosion Protection of Outdoor Iron Artifacts Using Commercial Rust Converters."

Journal of the International Institute for Conservation – Canadian Group 20 ( 1995 ), pp. (printed pages) 26-40.

Selwyn, L. Metals and Corrosion: A Handbook for the Conservation Professional. Ottawa, ON: Canadian Conservation Institute, 2004 .

by Judy Logan revised by Lyndsie Selwyn, Clifford Cook and Tara Grant

Originally published 1989 Revised 1997 , 2007 , 2013

Copies are also available in French.

Texte également publié en version française.

© Government of Canada, Canadian Conservation Institute, 2014 ISSN (International Standard Serial Number) 0714-6221

Date modified: 2019-02-22

Evolution of historical riveted connections:

joining typologies, installation techniques and calculation methods

Q. Collette, I. Wouters & L. Lauriks Department of Architectural Engineering (ARCH), Vrije Universiteit Brussel, Belgium

Abstract

Riveting was one of the major joining techniques used for the assembly of iron and steel structures. Being widely used since 1860, today most of the existing riveted structures need maintenance and possibly strengthening.

This research aims to improve the existing knowledge on this type of fasteners in order to stimulate less intrusive interventions during renovation, respecting the historical character of these structures. To reach this goal, a multidisciplinary literature study is carried out, dealing with three related topics:

historical analysis (historical context, fields of use, types of riveted connections, comparison with other contemporary joining techniques), technical subjects (definition, material, joining typologies, forms of the rivet head, installation processes and techniques) and structural understanding (bearing principle, strength of riveted connections, calculation methods).

Keywords: riveted connections, iron and steel, historical analysis, technical know-how, structural understanding, joining typologies, installation techniques, calculation methods.

1 Introduction

Although considered as an emblematic type of fastener characterizing 19th and 20th century iron and steel constructions, riveted connections were first introduced by two other branches of industry, namely boilermaking and the shipbuilding industry. Thanks to the advent of the industrial revolution and the major technological innovations of the iron and steel industry, rivets became massively and widely used for various constructions (civil engineering, Structural Repairs and Maintenance of Heritage Architecture XII 295 www.witpress.com, ISSN 1743-3509 (on-line) WIT Transactions on The Built Environment, Vol 118, © 2011 WIT Press doi:10.2495/ 10251STR1 private/public buildings) and applications (trussed beams, built-up shapes,…).

Though less visible, the riveting technology experienced an important dimensional, conceptual (design) and technical evolution over time. As a consequence, today’s engineers and architects have to manage this complexity on a regular base, given the large number of historical structures that need renovation or maintenance. The literature study presented in this paper aims to provide – by combining historical, technical and structural aspects – the necessary know-how to understand the original design and to assess the historical character of the structure, at the micro-level of its joints. To reach this goal, international (Belgium, France, the United Kingdom, the Netherlands) historical handbooks, patents and norms were consulted, in combination with more recent reference works [1, 2].

2 Historical context

As early as 3000 BC, the rivet made its first appearance in Egypt as a joining element for the manufacturing of several tools and objets d’art (e.g. fixing a handle on jars). Later, it became a fastener commonly used during the Gallo- Roman era. Already, they designed a kind of rivet mould – the ancestor of the cup tool commonly called these days “bouterolle” – to joint metallic plates (boilerwork). In a more recent past, the Vikings resorted to rivets for installing the planking of their boats in the 7th and the 8th century [1, 2].

2.1 1840-1930, the heyday of rivets

The development of the riveting technique and its applicability in practice is closely correlated with improvement and evolution of the materials to be joined.

For instance, as long as wooden constructions were approved by a large majority and widely used, riveted connections, given the large thickness of the to assemble parts and other structural disadvantages (e.g. buckling of the rivet shank, splitting risk, ...), were not a fitted and convenient alternative. On the other hand, important developments in the field of iron and steel industry since the beginning of the 19th century allowed to overcome the main barrier to entry, namely the overall thickness of the joint. Shapes made of wrought iron and (mild) steel, with their slender cross sections and their more ductile behaviour in comparison with cast iron (impossible to rivet), stimulated and symbolized the dawn of a new “joining era” [3].

From 1840 onwards, riveted connections became the most important joining technique within different fields that followed and overlapped each other. The use of rivets had experienced several – formal, constructional and theoretical – renewals and evolutions, being in phase with industrial and technical “brainwaves” of that time (e.g. new materials, manufacturing process, installation techniques,...). The heyday of rivets started to decline around 1930, supplanted step-by-step by another joining technique: electric arc welding [1, 2].

296 Structural Repairs and Maintenance of Heritage Architecture XII

2.2 Fields of use

In contrast with the welding technique that characterizes one major field of use (metallic constructions), rivets benefitted from a larger applicability within the industrial landscape. From 1810 onwards, the boilermaking was the first to introduce hot riveting, namely heating the rivet before riveting. Steam engines and later locomotive’s boilers were manufactured thanks to this technique until the beginning of the 20th century. The shipbuilding industry is the second field of use (1830-1940). This can be explained by the exponential growth of the maritime traffic and commercial exchanges. Around 1840, riveted connections made their appearance in the last major industrial sector: iron and steel constructions. Riveting, as a new way to assemble elements together, influenced and contributed to rationalize the manufacturing processes of this industry already at the design stage. Moreover, riveted connections gave an answer vis-à-vis the expectations and wishes of engineers and architects (e.g. Art Nouveau architect Victor Horta) who wanted to explore new formal and conceptual languages (apparent lightweight structures, transparency in combination with glass, ...), according to the social, economical and cultural mutations of that time [4].

The typical applications of riveted connections for metallic constructions can be merged into two main groups: civil engineering and public/private buildings.

Although the built structures of the first group, mainly motorway and railway bridges, are better-known, several smaller scaled constructions met in buildings were joined with rivets, for example winter gardens, industrial and exhibition halls, private houses, department stores and schools.

From a more local point of view, this fastener has two principal functions:

connecting structural elements and manufacturing built-up shapes. Portal frames and trussed beams are representative examples of typologies where rivets, often in combination with bolts, connect, with or without additional connecting element (angle shape, gusset,...), iron and steel plates together. The second main function is related to the manufacturing of composed beam types made of shapes or twin beams (built-up girders and columns) [4].

The advent of both a new joining technique and a new material, respectively welding and (reinforced) concrete, led from 1920-30 riveted connections on a slippery slope regarding their use in the building sector [1].

2.3 Rivets versus bolts and welding

Rivets are fixed, in opposition with mobile connections, and permanent which means they cannot be dismantled. In comparison with bolts, their main advantages are their cheapness and the better stiffness provided to the joints. On the other hand, bolts will be privileged in case of large diameters and/or length of the shank, required dismantling, joining of cast iron shapes, etc. Regarding welding, its first technical diseases and the generated distrusted climate explain why riveted connections were still in use until 1970. Nevertheless, structural (self weight, weakening of the structure [rivet holes]), financial (labour costs)

Structural Repairs and Maintenance of Heritage Architecture XII 297 and practical (noisy/difficult job) issues sounded the death knell for riveting connections that were, from 1940 onwards, gradually replaced by welding [1, 5].

3 Rivets, definition and technique

3.1 What’s a rivet?

According to Francken [6], a rivet consists of a cylindrical shank and a rivet head, usually rounded: “Le rivet est une sorte de clou à section cylindrique et à tête ordinairement ronde qui sert à assembler les tôles et dont l’extrémité a été aplatie et élargie après coup de façon à former une seconde tête.”. The rivet is put through the rivet hole and a second rivet head is formed – the forged head – to pull the connecting elements towards each other, fig. 1.

Figure 1: (Left) Example of a rivet and its original round head [7]. (Right) The three main components of a rivet (single lap joint): (A) the rivet shank, (B) the forged head and (C) the original head [8].

Study of historical sources shows that engineers, theorists and builders of the time were aware of the importance of rivets as a critical part within the whole structure. The choice of material for manufacturing a rivet, which is an initial crucial aspect, was the subject of many discussions and debates [9]. In most cases, it was preferable to opt for a material with approximately the same or slightly lower mechanical properties than these of the elements to be joined.

Even if the quality and the price of steel rivet were satisfactory, iron and puddle iron were still considered as the best alternative at the end of the 19th century.

Indeed, before the development and the widespread use of mechanical riveting (1895-1910), the difficult installation processes discredited rivets made of steel, which was even forbidden by some countries, such as Russia, for the connection of steel plates and/or shapes [5]. Then, results of experimental tests were published by several authors such as Frémont [10] on the strength of materials.

Combined with the growing awareness on the importance of the quality of the rivet, these experiments reconciled engineers and builders with the use of steel rivets (e.g. “extra mild steel”) [3, 11].

298 Structural Repairs and Maintenance of Heritage Architecture XII

3.2 Rivet head: the reflection of structural, constructional and financial aspects

At first, a large formal and dimensional variety of rivets heads was available.

The broad dimensional diversity had been channelled and rationalized via norms from the 1920s onwards. At the same time, given their expensiveness and complex manufacturing, particular forms of rivet heads fitted for a specific use were “naturally” ousted [2]. The choice of a rivet head depends on the joining type (load and/or fluid tight riveting), practical matters (installation) and aesthetic considerations. Different forms were utilized for both the original and the forged rivet head, which were not necessarily the same per rivet. The main types of rivet heads, irrespective of the field of use, are: round, countersunk, coned and flat heads. For iron and steel constructions, the round head was the most common one.

Moreover, these forms were a research subject during approximately 100 years. The main parameters that characterized this evolution are the improvement of installation methods, results of experiments, and financial aspects. From 1820 onwards, the development of manufacturing machines and later riveting machines generated the progressive dominance of the round head, to the detriment of the coned head. Also, research on the weight and the price of riveted connections, especially on the head depth (h), was carried out. As a result, the “round head” made room for two derived improved forms: the round snap head (perfectly hemispheric, higher head depth) and a more flattened version, the button head also called “en goutte de suif” (with two radiuses of curvature) [2, 5].

Table 1: (Left) List of authors/organisation and the date of their publication.

(Right) Evolution of the design proportion of round head: ratio “D/d” (diameter of the head/diameter of the shank) and ratio “h/d” (head depth/diameter of the shank).

Structural Repairs and Maintenance of Heritage Architecture XII 299

Quantitative results of this literature study, which confronts publications of several authors [1, 3, 6–9, 12, 13], clearly show the formal evolution of the round head to one of its follower namely the round snap head (hemispheric):

decreasing values of the “D/d” ratio combined with increasing values of the “h/d” ratio, tab. 1.