Repairing Cast Iron Tubs: Paint Over Dings

Dingy cast iron tubs can be revitalised with a fresh coat of paint. Cast iron tubs are often old and may have paint containing lead, so it's important to take the necessary precautions when removing old paint. The process of refinishing a cast iron tub involves several steps, including cleaning, sanding, filling in cracks, applying primer, and painting. With the right tools and preparation, you can give your cast iron tub a new lease of life and a stylish update.

Sanding down the tub's surface

Sanding down the surface of a cast-iron tub is an important step in the refinishing process. It helps to create a smooth, long-lasting finish that doesn't flake or peel. Before you begin sanding, it is crucial to ensure that the surface is thoroughly cleaned and degreased. Use a trisodium phosphate (TSP) substitute cleaner or a heavy-duty degreaser with an abrasive pad to remove all built-up grime, soap scum, hard water stains, and rust from the tub's surface.

Once the tub is clean, it's time to sand. Using 80-120 grit sandpaper, vigorously sand the entire tub, paying close attention to corners and crevices. This process will help create a rough surface for the new finish to grip properly. It is important to be thorough during this step, ensuring that the surface feels thoroughly deglossed. If there are any areas of stubborn rust that won't come off with sanding, treat them with a rust converter product designed for cast iron bathtubs.

After sanding, be sure to wipe away all the sanding residue. If there is any remaining paint on the tub, it is important to sand down the leading edge of the paint so that it blends in with the level of the bath and does not stand out. This can be done by feathering the paint's edge with sandpaper.

In some cases, you may need to consider sandblasting the cast iron tub. This process reduces imperfections and achieves an even smoother surface. Sandblasting is especially useful if the tub has been painted before, as it will need to be stripped and sanded, requiring additional work and expense.

Once the sanding is complete and the surface is properly prepared, you can move on to the next step of applying a primer.

Filling in cracks and scratches

Once the surface is smooth, you can start filling in the cracks and scratches. For deeper scratches, it is recommended to use a metal-etching primer, such as a galvanized metal-etching primer, as it promotes acidic bonding and adheres well to cast iron. This will ensure that the cracks and scratches are properly filled and that the new paint will have a smooth surface to adhere to. Apply several coats of primer, allowing each coat to dry before applying the next.

If you are dealing with smaller scratches, you can try using a cleaner that is harder than the scuff but softer than the glazing. Baking soda, for example, can be used to scrub away scratches without damaging the glazed porcelain shell. Simply wet the scratch with peroxide, sprinkle baking soda on it, cover with a white paper towel, and then pour peroxide over the whole thing. Leave it overnight, and the scratch should be gone by morning.

After filling in the cracks and scratches, you can move on to the next step, which is usually applying a top coat of paint. It is important to choose a paint that is suitable for cast iron tubs, as certain compounds can damage the surface. Water-based latex and acrylic primers, for example, should be avoided as they will cause flaking within months of application. Instead, opt for an epoxy finish or a specialized product like the Rust-Oleum Tub and Tile Refinishing Kit.

Applying a primer

Surface Preparation:

Before applying the primer, it is essential to prepare the surface of the tub thoroughly. This includes removing all peeling paint and rust spots by sanding or sandblasting the tub's exterior. Sandblasting can be an effective method to reduce imperfections and achieve a smoother surface. Ensure that you work in a well-ventilated area and take the necessary safety precautions, especially if the old paint may contain lead. It is recommended to consult a professional or a resurfacing consultant if you are unsure about the condition of your tub or the appropriate safety measures.

Primer Selection:

Choosing the right primer is critical for a durable finish. Water-based latex and acrylic primers should be avoided for cast iron tubs as they can cause flaking due to the nonporous nature of the cast iron surface. Instead, opt for a primer specifically designed for metal surfaces, such as a galvanized metal-etching primer or an epoxy primer. These primers promote better adhesion and bonding, reducing the likelihood of flaking or peeling.

Application Technique:

When applying the primer, follow the manufacturer's instructions for the best results. Use a small roller or a brush for a controlled application, ensuring that you cover the entire exterior surface of the tub evenly. Pay attention to the drying time between coats, as some primers dry relatively quickly, allowing for multiple coats in a short period.

Multiple Coats:

Applying several thin coats of primer is generally recommended for cast iron tubs. This helps create a more durable and consistent finish. The number of coats may vary depending on the primer used and the condition of the tub. For example, a tub with extensive rust or peeling paint may require more coats to achieve a smooth and even surface.

Drying and Curing:

Allow sufficient time for the primer to dry thoroughly between coats and before proceeding to the next step, which is usually painting. Refer to the primer's instructions for specific drying times and conditions. Proper drying and curing ensure that the primer adheres correctly and forms a strong bond with the cast iron surface.

By following these detailed instructions and tips, you can effectively apply a primer to your cast iron tub, creating a solid foundation for a long-lasting and aesthetically pleasing paint job.

Using the right paint

Painting a cast iron tub requires careful preparation and the use of the right paint to ensure a long-lasting and attractive finish. The first step is to assess the condition of the tub and determine if it needs to be stripped and sanded. If the tub has been painted before, it may need to be completely stripped to achieve a smooth surface. This step may require additional work and cost, but it is crucial for achieving the best results.

Once the tub is stripped, it is important to remove all traces of silicone seals as the new paint will not adhere properly to any silicone surfaces. After ensuring that all silicone is removed, the next step is to apply a suitable primer. A galvanized metal-etching primer is recommended for cast iron tubs as it promotes acidic bonding and adheres well to the cast iron surface. It is important to avoid water-based latex and acrylic primers as these are not suitable for cast iron and will result in flaking within a few months.

When choosing the paint for your cast iron tub, opt for an epoxy finish to prevent future rust. An example of a suitable product is the Rust-Oleum Tub And Tile Refinishing Kit, which is ideal for bathtub revamps. This kit is suitable for steel baths but not compatible with acrylic baths. After applying the primer, you can apply several coats of paint, following the specific instructions for the product you have chosen.

In addition to using the right paint, proper preparation of the tub is essential. Start by setting the tub upside down and removing any loose paint or rust with a pressure wash or a more aggressive method like a wire cup wheel if there is extensive rust. If the tub has lead paint, take the necessary precautions and consider using a lead paint test kit for safety. Once the tub is clean and smooth, you can proceed with priming and painting, ensuring that you do not paint the enamel coating on the inside of the tub.

Buffing and polishing

Firstly, it is important to fill in any dings, scratches, or cracks with putty. This will create an even surface and ensure that the final finish is smooth and free of imperfections. Once the putty is dry, you can begin the buffing process.

For buffing, you can use a power buffer with a foam pad, an auto compound, or a low-speed auto buffer. These tools will help remove any scratches and create a smooth base for the final polish. It is recommended to use a power buffer, especially if you are aiming for a high gloss finish. However, if you are unable to access a power buffer, you can also hand buff the tub with a soft cloth and polymer glaze car wax. This process may require more elbow grease but can still achieve a shiny finish.

After buffing, the next step is polishing. To achieve a high gloss shine, you can use polishing wheels, especially those designed for polishing porcelain. Alternatively, you can use a soft cloth and a suitable polishing compound, such as 3M Finesse II compound, to polish the surface by hand. This step may require multiple attempts and different combinations of abrasives to achieve the desired shine.

Finally, it is important to note that if your tub has been previously painted, it is crucial to strip and sand the surface before beginning the buffing and polishing process. This will ensure that the new finish adheres properly and does not flake or peel over time.

Frequently asked questions