A pictorial survey of eight case studies suggests that using marine grade castings and a special application finish to avoid degassing results in long lasting beautiful aluminum castings, even in harsh salt water environments


Marine-grade-01Yet there’s even something better then powder coating! You want great looks and long life from your new outdoor wrought iron, aluminum metal doors, fences, gates, driveway entrances, and balcony railings. If you live in a severe weather environment, or near the ocean, special care and preparation must be applied to that product. To avoid deterioration, first, a ‘Marine Grade Casting’ is necessary… which is a special mixture of various metals for added protection. Unfortunately, some wrought iron companies will not make you aware of this to keep their material costs low. Avion Metal Works of Florida includes ‘Marine Grade Casting’ as a standard practice. Please read on for important information.

These spear points illustrate the coherent coating of marine grade castings in excellent condition after one year on the beach.

There are many steps necessary to providing a good, hard, coherent coating to aluminum castings. These steps include proper cleaning and rinsing, degassing, and proper curing of the coating. However, even if these steps are followed, sufficient evidence from on-site inspections and field reports suggests that another step is necessary on your part: using marine grade base material. The marine grade approach offers added protection for long life and better looks. Also: See our article’ ‘Wrought Iron or Aluminum. The Choice’. The rapid flaking and peeling of coatings from aluminum castings in a severe weather environment or normal slower deterioration in a milder environment can be resisted with the proper selection of marine grade base metal aluminum casting to resist corrosion and improve coating performance.

Corrosion on aluminum

This scroll casting is not marine grade. It shows severe white corrosion after only 18 months in its ocean environment in Sarasota, Florida. No coating remains.

Flaking and peeling occur on regular aluminum because air penetrates through the coating and corrodes the base metal. The devastation of the coating can occur rapidly when the product is next to the ocean. The scroll casting pictured at left has been near the ocean only 18 months and shows almost complete disintegration.

POOR: Corrosion on non-marine grade castings. Typical corrosion of non-marine aluminum castings is shown at left. The ball cap below left, has been near the ocean for four years and shows corrosion on the corner edges where only a thin layer of coating might have been applied. This edge with a thin coating enables the salt air to penetrate here first and begin the corrosion peeling action. The root cause of the white chalk aluminum corrosion is residual amounts of copper creating a galvanic reaction with the aluminum base material.

BETTER: Corrosion on marine grade casting. Pictured below is a handrail installed near the ocean in Palm Beach, Florida. For eight years the castings have been directly exposed to the wind and spray of the ocean. However, they are still shiny and coherent. This shiny and coherent surface indicates no galvanic corrosion has occured as the marine metal has successfully resisted the salt air.

This flower panel in West Palm Beach, Florida, shows flaking because of a poor coating job. But its marine grade castings are still shiny and coherent after eight years.

This 2″ ball cap is not marine grade. It shows chalk corrosion and flaking (starting at corners) after four years on the Indian River in Vero Beach, Florida.

BEST: Corrosion on marine grade D castings.A recent on-site survey of many copper-free marine grade castings that have been on the ocean up to3½ years shows the excel-lent results of combining marine grade castings with coating applications.

This aluminum rail with marine grade aluminum cast collars also shows a coherent coating in excellent condition after three years on Florida’s Intracoastal Waterway.

Please Contact Avion Metal Works of Florida so we may help and inform you of the impor-tant various aspects of purchasing aluminum,wrought iron, and metal products.

For your information

Poor finish: Non-marine grade castings and finishing application

Best finish: Marine grade castings, proper preparation, and quality finishing.