Treating surface rust properly for maximum container life span
Warning- Do not get acid on skin or in your eyes. Most of the products we recommend here are unhealthy to breathe. Always use a properly working double respirator made for organic vapors, and professional grade particle mask when grinding. Thank you!
Step one- Get a small, light weight, high rpm (12,000 minimum) grinder- 4.5” is a recommended diameter, but any size will work. We recommend the bosch 7.2 amp grinder available at gaspro, it is the cadillac of grinders, and only costs $78. You can use the ¼” thick metal grinding discs or the thin cutting discs to grind off the thicker rusted areas. Large, heavy grinders will wear you out quick, they buck too easily, do not spin fast enough and are not at all recommended. Grind off the rust that is flaking on the surface down until you hit metal. Don’t worry about grinding every tiny rust vein inside the metal, just get everything off until you get to bare metal with little veins of rust inside the metal, and do that everywhere on the container. Do step two as soon as possible, don’t leave bare metal unprotected for more than 12 hours. If you want to avoid step 2 (acid treatment) all together, you can apply two coats of rust bullet on just the rusted spots, not on entire container. Rust bullet is rated number one by the US Navy to seal off the elements from the metal. It is super expensive, but our extensive use of the product shows us that it does in fact work. Once that cures for a few days, you prime and paint with industrial oil based paint.
Step two- Apply the zinc phosphate acid treatment made by the EZ clean company called etch and prep, available at home depot for about $15/gallon as directed, apply liberally onto the grinded metal and let it sit for 4 or more hours. A pressure washer is the best if you can get one to blast off the rust in those deeper veins that the acid has eaten. I usually do 2-3 acid treatments on the rust, washing with a pressure sprayer after each application. This is easier than grinding into those veins forever with the grinder. When you have eaten down to bare metal as best as you want to do, wash the entire container with industrial grade liquid detergent and a large, abrasive green scrubby cloth. We recommend using a drywall sanding swivel pad and pole and attaching two large green scrubby cloths that are sewn together to the large rectangular swiveling pad. This is because they don’t seem to make a green scrubby long enough to reach across the swivel pad. The swivel pole pad fits inside the corrugated metal surfaces of the container really well. Doing this on your hands and knees is not fun!
From this point, you have two processes to choose from- doing it well or doing it exceptionally well. I will start with doing it well:
How to do it exceptionally well
Option 1- Apply two coats of rust bullet on just the rusted spots, not on entire container. Rust bullet is rated number one by the US Navy to seal off the elements from the metal. It is super expensive, but our extensive use of the product shows us that it does in fact work. Once that cures for a few days, you prime and paint with industrial oil based paint. The other option is POR-15, which is very good also. The difference is rust bullet leaves an epoxy vapor barrier coating and can be left not top coated, whereas the POR-15 MUST be top coated, it breaks down from UV.
Once container is totally dry after the washing, apply one coat of the POR-15 rust treatment only on the grinded metal areas with a brush (not on entire container) and apply a second coat 20 minutes later approx. Two coats of POR-15 is essential! You cannot spray it, and a roller is wasteful, so use a large brush for big areas. Do not apply second coat of the POR-15 earlier or much later. Once all grinded areas have 2 coats of POR-15, let cure 24 hours or whatever the can says (I believe 24 hrs is right). Kona Marine or J&J hardware in Hilo are the only places to get POR-15. You can also order it online, just google POR-15 to get to their site. It is about $45 per quart, and goes a fairly long way. You need to wear a good double respirator as the fumes are horrendous, and there is no solvent to break it down, so don’t spill on yourself or anything important. Once you open a can, you need to use the whole can fairly quickly as it doesn’t store very long. I pour it into multiple smaller mason jars and use 1 entire 8 oz mason jar in one sitting. Be sure to not have much air in the mason jars, and cap tightly right away. I have successfully stored it that way for several months. Air exposure will cause the POR-15 product to get thick and set-up really quickly. This product is the best defense against rust in the world if you use it properly as I explain in this article. Once the POR-15 cures as directed by the company, then prime and finish paint as described above, right away. The POR-15 shuts out oxygen and water vapor exceptionally well, but it needs the industrial oil top coats as the sun breaks down POR-15 fairly quickly. Rust bullet is also a good coating that is similar to POR-15.
Heat-reflective & waterproofing coatings are recommended
To reflect the suns heat and also protect your containers roof from rusting, we highly recommend applying either silicone elastomeric waterproofing compound or acrylic based elastomeric coatings. The silicone elastomerics are the ultimate vapor barrier, and the most resilient to ponding water on the roof. They also reflect heat incredibly well. They are more expensive than acrylics, but are better at waterproofing your roof. Acrylic elastomeric coatings are very good to apply to walls where waterproofing is not nearly as much of a concern as the roof is. For those needing to cool off a hot metal roof and also catch water off of the roof, only the acrylics are NSF rated for safe water catchment. We recommend a particular brand which has an additive that makes it hold up much better under ponding water. We can supply you with the product, ship and deliver it, call for info and pricing. (If the elastomeric coatings are too much hassle or cost for you, you can achieve some degree of cooling if you use a very light color paint, and the high gloss recommended here also helps reflect heat.) However, for the roof, silicone elastomeric is the best way to go, and will give your container many more years of service without holes in the roof from ponding water.
If you use either elastomeric coating, then you only need to use the oil based enamel on the grinded areas and not on the entire container. Even if you opt for either of our more extensive rust treatment processes in the topmost articlw above, elastomeric coatings are recommended to reflect heat. Both the silicone and acrylic elastomerics utilize a water-based epoxy primer that you can use on top of oil based paint once it has cured for only 2 days approx. The primer sticks to anything, like a magnet. Do not ever use any elastomeric coating without first using the recommended primer. Bonding is everything! Contact us to order primer and the silicone or acrylic based elastomeric products at the lowest prices. 953-2005
Always keep containers off the ground. Moisture wicks up from the ground, from a concrete slab and also on blacktop. We use 16” X 16” X 5” thick blocks from Home Depot, they cost about $10 each. Call us for recommendations on how to do this properly. Unfortunately, it is much too much trouble to treat underneath the container floor, but if you’re off ground, container floors rarely rust out completely unless you are right on the ocean. If you are concerned, you can put a rust-proofing compound from Sealmaster called Flexmaster over the rusted areas underneath to help starve the rust from air and moisture. This product is quite effective, and the cost is very reasonable.
To conclude- it is so much easier and cheaper to work with a new or premium grade container. Doing all this rust work and paying for all these expensive paints is not cheap and the labor is not fun. If you pay someone to grind the rust, you will pay a ton of money, so be smart and buy a new or premium grade container and all you will need to do is keep it painted every 4-5 years or as needed. We do recommend silicone elastomeric coating applied on the roof of any container to prevent rust from ponding water. The floor on a new container is not rusty, it has fresh undercoating, so you do not have to worry about your structure crumbling after all the money you spend building it out. On our used premium grade containers, the steel floor components are generally less rusty, and you can apply rustproofing materials such as flexMaster, made by Seal Master, or similar for a satisfactory result. Insulation inside is good, but not without reflecting as much of the sun's heat from the outside as possible. A metal container structure behaves like a wood home with elastomeric coatings applied to the roof and west-facing wall, or to all surfaces if desired. We can supply you with the proper coatings and also instruct you on how to use them properly. 953-2005