Removing Paint from Wrought Iron, Cast Iron and Steel Using Chemical Methods
- Procedure code:
- Developed by NPS Southeast Regional Office
- Metal Materials
- Last Modified:
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REMOVING PAINT FROM WROUGHT IRON, CAST IRON AND STEEL USING CHEMICAL METHODS
TAKE SPECIAL CARE TO PROTECT ALL ADJACENT MATERIALS, FROM DAMAGE BY SPLASHING OR RUN OFF THAT MAY CONTAIN CLEANING OR STRIPPING PRODUCTS AS WELL AS PAINT, FINISHES AND SOILING REMOVED FROM TREATED SURFACES. DO NOT USE THIS PROCEDURE ON METALS OTHER THAN THOSE SPECIFIED. REVIEW MANUFACTURER'S CAUTIONS AND APPLICABLE FEDERAL, STATE AND LOCAL REGULATIONS GOVERNING PRODUCT USE AND CONTROL OF HAZARDOUS MATERIALS BEFORE UNDERTAKING WORK INVOLVING REMOVAL OF PAINTS AND COATINGS; ADJUST PRODUCT SELECTION AND METHODS ACCORDINGLY. TEST MILDEST, MOST ENVIRONMENTALLY BENIGN FORMULATIONS FIRST BEFORE PROCEDING TO STRONGER CHEMICALS AND HARSHER METHODS.
1.01 SUMMARY A. This procedure includes guidance on chemically removing paint from wrought iron, cast iron and steel. These metals should be repainted immediately following paint removal in order to prevent exposure to the atmosphere and subsequent corrosion.
B. For information on painting and coating these materials see 05010-13-S "Primers and Paints for Wrought Iron, Cast Iron and Steel", 05010-18-R "Applying a Sacrificial Coating to Wrought Iron, Cast Iron and Steel", and 09900-07-S "General Guidelines for Painting Exterior and Interior Surfaces".
C. Chemical methods as used herein shall apply to the use of commercial chemical paint strippers and rust removers.
D. There are several causes for paint failure on metal. Excess moisture can cause rusting. As metal rusts, the rust expands breaking the bond between the metal and the paint. Inadequate or improper surface preparation can interfere with the proper bonding of the new paint. The wrong primer can cause anything from pitting of the metal surface to peeling of the new paint.
E. It is not necessary to remove all previous coats of paint if:
1. they are adhering soundly,
2. the new painting system is compatible,
3. important design details are not being obscured by the paint layers.
F. An archives of the paint history of the building is to be maintained. This is to include the paint samples taken during research, samples of the new paint colors and the manufacturers technical information.
G. Safety Precautions:
1. No food or drink shall be allowed near any work station so as to prevent contamination from paint, paint chips or paint dust which may contain lead and other toxic substances.
2. Paint being removed most likely will contain lead. All workmen must wear protective clothing, (including hair), goggles and respirators with proper filters.
3. Protective clothing shall be removed at the end of each day and kept at the site to prevent workers from taking dust and paint chips to other parts of the site or to their homes.
4. Wash hands and face often, especially before eating and at the end of the day.
5. All waste material shall be collected at the end of each work day and disposed of in a manner consistent with local environmental regulations. It is considered Hazardous Waste.
6. Work area shall be sealed to prevent the spread of paint dust and debris beyond the work site.
7. After paint removal is complete, all areas around the building shall be cleaned of all paint dust and debris, and such debris shall be properly disposed of in a manner consistent with local environmental
H. See 01100-07-S for general project guidelines to be reviewed along with this procedure. These guidelines cover the following sections:
1. Safety Precautions
2. Historic Structures Precautions
4. Quality Assurance
5. Delivery, Storage and Handling
6. Project/Site Conditions
7. Sequencing and Scheduling
8. General Protection (Surface and Surrounding)
I. For additional information on cast and wrought iron see the following procedures:
1. 05010-04-S, "Cast Iron: Characteristics, Uses and Problems."
2. 05010-11-S, "Wrought Iron: Characteristics, Uses and Problems."
3. 05010-01-S, "Checklist for Inspecting Cast Iron Failures."
A. For Chemical Paint Removers:
1. ProSoCo, Inc
2. Star Bronze Co.
3. Savogran Company
4. Deidrich Technologies
NOTE: Chemical products are sometimes sold under a common name. This usually means that the substance is not as pure as the same chemical sold under its chemical name, but the grade of purity of common name substances, is usually adequate for stain removal work, and these products tend to be less expensive. Common names are indicated below by an asterisk (*).
A. Chemical Paint/Lacquer Removers:
1. Manufacturer's standard thixotropic formulation for removing paint coatings from ornamental metal work. Review manufacturer's literature to identify least hazardous products that may be effective for initial testing. Examples include: "Envirestrip" (Diedrich Technologies), "EnviroKlean Safety Peel 1" (Prosoco, Inc.), Zip Strip 2 (Star Bronze Co.) and"Biodegradable Stripeeze" (Savogran Co.)
2. Semi-paste, water rinsing, nonbenzol remover such as "Strypeeze Semi-Paste" (Savogran Company), or approved equal.
a. Characteristic orange color.
b. Will work on both latex and oil-based paints, lacquers and varnishes.
c. Cling well to round or vertical surfaces.
d. Form an anti-evaporative film as they dry.
e. Clean-up by either washing or scraping off. All traces must be removed and a neutral pH achieved before repainting.
f. Use if milder formulations are not effective.
3. Non-flammable, heavy bodied, methylene-chloride based remover such as "Super Strip Non-flammable", "Zip-Strip" (Star Bronze Co.), or approved equal.
a. Good for interior use because they are non-flammable.
b. Will soften oil-based paints, lacquers, varnish and synthetic baked finishes.
c. Because they are so heavy bodied they will cling to vertical and irregular surfaces.
d. Use if milder formulations are not effective.
4. Non-flammable, water rinsing, liquid remover such as "H2O Off", or approved equal: Available from paint supply store.
a. Methylene-chloride based strippers excel in speed and effectiveness but produce toxic fumes and waste, limiting (in some locations prohibiting) their use. Test milder, non-hazardous formulations first.
b. Will soften oil-base paints, varnish, and synthetic baked finishes.
c. Will not work on vertical surfaces. Good for horizontal surfaces.
5. Liquid benzol remover such as "Kutzit", or approved equal: Available from paint supply store.
a. HIGHLY FLAMMABLE AND TOXIC. WEAR PROTECTIVE CLOTHING. USE IN WELL VENTILATEDAREA, DO NOT USE NEAR FLAME, SPARKS, ORHEATERS.
b. Will remove oil-based paint, lacquer, varnish and synthetic baked finishes.
c. Work well on flat surfaces. Work quickly.
B. Chemical rust removers, such as "Navel Jelly", or approved equal.
C. Cornstarch or fumed silica to further thicken chemicals so they will adhere to vertical surfaces.
D. Liquid Strippable Masking Agent: Manufacturer's standard liquid, film forming, strippable masking material for protecting glass, and polished stone surfaces from damaging effect of acidic and alkaline cleaners, such as "Sure Klean Acid Stop" (ProSoCo, Inc.), or approved equal.
E. Mineral Spirits: (To remove chemical residue)
1. A petroleum distillate that is used especially as a paint or varnish thinner.
2. Other chemical or common names include Benzine* (not Benzene); Naphtha*; Petroleum spirits*; Solvent naphtha*.
3. Potential Hazards: TOXIC AND FLAMMABLE.
4. Safety Precautions:
a. AVOID REPEATED OR PROLONGED SKIN CONTACT.
b. ALWAYS wear rubber gloves when handling mineral spirits.
c. If any chemical is splashed onto the skin, wash immediately with soap and water.
5. Available from construction specialties distributor, hardware store, paint store, or printer's supply distributor.
F. Phenolphthalein: Used to test pH of a surface after stripping with chemicals or any alkaline product. Available at some drug stores or chemical supply houses.
G. Trisodium Phosphate and TSP Substitutes
DUE TO ENVIRONMENTAL HAZARDS OF PHOSPHATES, TSP IS PROHIBITED IN SOME LOCATIONS. USE ONLY AS NEEDED AFTER TESTING ALTERNATIVES FOR CLEANING EFFECTIVENESS.
1. Strong base-type powdered cleaning material sold under brand names.
2. Other chemical or common names include Sodium orthophosphate; Tribasic sodium phosphate; Trisodium orthophosphate; TSP*; Phosphate of soda*.
3. Potential Hazards: CORROSIVE TO SKIN.
4. Available from chemical supply house, grocery store or supermarket, hardware store or paint store.
5. Substitute products include Klean-Strip 0408 TSP Trisodium Phosphate Substitute No-Rinse (Prosoco, Inc.) and water-based solutions containing baking soda or borax.
H. Soft cloths
I. Steel wool
J. Plastic sheeting and duct tape to cover the stripper during dwell time.
A. 000 steel wool or synthetic pads
B. Scrapers and small picks to remove sludge
C. Steel or brass wire brushes
D. Fiber bristle brushes (1/2 to 3/4 inches long)
E. Metal containers such as old coffee cans in which to
dispose of sludge
A. Before work is begun on removing the existing paint film or otherwise preparing the surface all sources of excess moisture shall be inspected and repaired or replaced as required.
1. Comply with recommendations of manufacturers of chemical cleaners for protecting building surfaces from exposure to their products.
2. Protect glass, unpainted metal trim and polished stone from contact with acidic chemical cleaners by covering them with liquid strippable masking agent or polyethylene film and waterproof masking tape. Apply masking agent to comply with manufacturer's recommendations. Do not apply liquid masking agent to painted or porous surfaces.
3. Protect unpainted metal from contact with alkali chemical cleaners by covering them either with liquid strippable masking agent or polyethylene film and waterproof masking tape.
4. Protect adjacent surfaces, including grass, shrubs and trees with paper, drop cloths and other means. Items not to be painted which are in contact with or adjacent to painted surfaces shall be removed or protected prior to surface preparation and painting operations.
5. All waste material shall be collected at the end of each work day and properly disposed of. It is considered Hazardous Waste.
6. Work area shall be sealed to prevent the spread of dust and debris beyond the work site.
7. If vacuums are used to clean area, machines shall be equipped with HEPA (High Efficiency Particulate Air) filters to insure all lead dust has been contained and removed.
3.03 ERECTION, INSTALLATION, APPLICATION
A. Rust Removal:
1. Brush apply commercially available chemical rust removers such as "Naval Jelly" (phosphoric acid), and allow to dwell according to manufacturer's instructions.
CAUTION: STAY AWAY FROM HYDROCHLORIC ACID BASED PRODUCTS AS THEY MAY LEAD TO FUTURE CORROSION.
2. Wipe off residue with mineral spirits and either steel wool or soft rags.
3. Dry immediately with clean soft cloths or using an industrial blow dryer. Follow direction of grain in metal. DO NOT TOUCH CLEANED ORNAMENTAL METAL SURFACE.
4. Prime immediately to prevent rust.
B. Clean small pieces which can be removed.
NOTE: REMOVE ONLY AS MUCH PAINT AND RUST EACH DAY AS CAN BE PRIMED THAT SAME DAY. BARE IRON AND STEEL WILL BEGIN TO RUST AGAIN WITHIN A MATTER OF HOURS. IT SHOULD NOT BE ALLOWED TO SIT UNPROTECTED OVERNIGHT.
1. Soak in a solution of hot water and TSP, TSP-Subsitute, or sudsy ammonia to loosen the paint.
2. Remove paint with scrapers and/or a wire brush.
3. A final wipe down with mineral spirits may be necessary to help remove final traces of paint.
4. Dry immediately and prime to prevent rusting. A heat gun, set at the lowest temperature, can be used to hasten the drying time. DO NOT USE HIGH HEAT AS THIS MAY DISTORT THE METAL MEMBERS.
C. Remove any loose paint not already removed with the rust using a chemical paint remover.
NOTE: IF THE PAINT IS ADHERING SOUNDLY LEAVE IT ALONE-IT PROVIDES EXTRA PROTECTION. FEATHER THE EDGES OF THESE AREAS TO PROVIDE A SMOOTH FINISH AND APPEARANCE.
1. Brush the chemical onto the surface in the amount recommended by the manufacturer. Thicken if necessary with cornstarch or fumed silica.
2. Cover with plastic and allow to sit or "dwell" according to the manufacturer's instructions.
3. Remove sludge using scrappers and steel wool. A second application may be required on those areas where paint is especially thick or the detail is intricate.
4. After removal has been completed using chemicals rub all surfaces down with mineral spirits to remove all traces of chemical and waxy residue.
a. To test whether all chemicals have been removed and a neutral pH achieved, dissolve a 2" piece of phenolphthalein in denatured alcohol.
b. Brush the solution onto the surface. If it turns a shade from pink to magenta there is still chemical residue.
c. Treat the surface with additional mineral spirits and continue testing until there is no color change in the phenolphthalein solution.
5. Dry thoroughly and prime immediately to prevent rust.
D. Paint all surfaces. For guidance see 05010-13-S "Primers and Paints for Wrought Iron, Cast Iron and Steel", 05010-18-R "Applying a Sacrificial Coating to Wrought Iron, Cast Iron and Steel", and 09900-07-S "General Guidelines for Painting Exterior and Interior Surfaces".