Do you like spending your valuable time polishing rusted stainless steel hardware or rust stains from gelcoat on your boat? If you are like me, you keep those unsightly stains off your boat, but don’t like the time it takes to keep up with the problem in the saltwater environment. The following boat maintenance tip makes removing these stains a breeze and is sure to make any proud boater smile.
First, a little education about stainless steel and rust stains. Stainless steel is common chromium/nickel alloy steel used in thousands of products from ocean-going craft to tableware. A protective chromium oxide film forms on its surface which gives stainless its superior corrosion-resistance property. However, stainless steel is not stain or rust proof. When the boat is used in a corrosive environment such as saltwater, water with high sulphur content, or polluted water, the stainless steel will periodically develop surface rust stains. This is perfectly normal under these conditions.
The following are the most common rust stain problems found on boats:
- Rust stains on stainless steel hardware and surrounding gelcoat caused by normal surface rust.
- Rust stains on stainless screw heads and surrounding gelcoat typically caused from contamination from ferrous metal screw drivers and driver tips.
- Rust specs on cockpit soles caused by small ferrous metal chips from fish hooks and tiny airborne ferrous metal particles from nearby projects or someone using steel wool near or on your boat.
- Rust stains on the transom from cast iron metal engine exhaust components on inboard and inboard/outboard powered boats.
The typical way to clean rusted stainless steel is to use a metal polish and protector on the stainless and a buffing compound followed by wax to clean fiberglass. The process is time consuming and requires a lot of elbow grease. Additionally, the process works well on SS hardware and small gelcoat areas, but is not practical for cleaning rust stained screw heads or rust specks on large cockpit and deck nonskid areas.
A much easier solution is to use a chemical cleaner called Ospho. Ospho is mild phosphoric acid solution manufactured by the Skybryte Company that is used for treating rusted metal and preparing it for painting. Ospho also is does an excellent job of removing the rust stains on stainless steel or gelcoat. It is great for cleaning rust stains off cockpit soles, deck nonskid and stainless steel screw and bolt heads. Not only does Ospho remove the rust stains, it passivates the surface of the stainless steel, which reduces future staining.
It is so effective that some high end boat manufacturers provide a bottle of Ospho rust stain remover with each new boat. Additionally, it is available at many local hardware, paint and marine supply stores. Sounds good doesn’t it?
Before we start, you need to be aware of the following.
- You should not apply Ospho directly on painted surfaces, chrome, and anodized aluminum or powder coated aluminum. It can damage these surfaces. You should only apply Ospho to stainless steel hardware, plastics and gelcoat. Ospho is completely harmless to these surfaces.
- Always read and follow all cautions and warnings on the label of any metal treatments such as Ospho. Ospho is a mild phosphoric acid solution that can dull some painted surfaces. Since it is an acid, it can cause mild skin irritation. Always use rubber gloves when working with Ospho.
- Oshpo can be used on some painted surfaces. Paint composition & quality vary greatly. If you decide to clean metal on or near a painted surface, test a small, hidden area. If dulling or peeling occurs, do not use Ospho.
Ok, now lets get started. Ospho is easy to use, but it is important to apply it properly. You should use the following procedure when using Ospho:
- Plan ahead and apply Ospho to clean fiberglass in the early morning or late afternoon when the sun is low.
- Use rubber gloves and follow all safety precautions listed on the Ospho container. It is also a good idea to use safety glasses or sun glasses just to make sure you don’t accidentally splash Ospho in your eyes.
Note: Although Ospho evaporates slowly; it could dry within 30 minutes if it is applied in direct sunlight during the heat of the day. You should avoid letting this happen on gelcoat. It will stain the gelcoat a light gray color if it is allowed to dry. It is best to use Ospho in the early morning or late afternoon when the sun is low. This will insure that it will have time to work without drying.
If Ospho dries and stains the gelcoat, scrubbing with soap and water or buffing with a fiberglass polishing compound will easily remove the stain.
Rusted stainless steel hardware and surrounding gelcoat or small gelcoat areas
- Estimate the amount of Ospho you expect to use and pour that amount into a plastic cup. Use a small disposable paintbrush to apply Ospho to the stainless or rust stained gelcoat.
- Allow it to work for 30 minutes, and then wash thoroughly with soap and water.
Specs of rust and rusted screw heads on large areas of gelcoat decks and cockpit soles
- Wash the area with soap and water and rinse well.
- While the gelcoat is still wet apply approximately ½ cup of Ospho for every 80 sq ft and spread with a deck brush.
- Allow it to work for 30 minutes, and then wash thoroughly with soap and water.
Other things that are good to know
- If heavy rust stains are still visible after the treatment, wait until the next day before you reapply Ospho. In many cases the stains will continue to fade for several hours after Ospho is rinsed off.
- Do not pour unused Ospho from the plastic cup back into the bottle. Product that has been in contact with metal will neutralize the contents in the bottle within several hours and it will no longer be effective.
I like to apply Ospho prior to cleaning the boat. That way, once the areas have been treated, I just wash the boat as I normally would to remove the Ospho. Once the boat is dry, you can apply a protective coating. A boat wax, metal polish, or a metal protector will shine and protect the stainless and reduce future rusting.
That’s it. The choice is yours; spend a few hours polishing your hardware and buffing your decks or give this a try and watch Ospho do the work for you while you drink an ice tea in the shade. Then, wash the boat and you are done.
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