Does Alumawood or Aluminum Patio Covers Rust?
Please note that I can only provide information about Alumawood by Omni-Max or Amerimax; other manufacturers or suppliers are not within my scope.
Most aluminum patio cover products generally don’t incorporate exposed components made from raw steel. Exterior fasteners are typically constructed from galvanized, hot-dipped, mechanically galvanized, double cadmium plated, aluminized, zinc electroplated, or 300 series stainless steel.
An incident occurred when a customer expressed concerns about rusty bolts and discolored washers on their patio cover over time.
After a brief examination, it became evident that the blackened areas were due to mold growth. This phenomenon can occur when the cover is neglected and not adequately maintained.
Upon my suggestion, the customer did clean the structure; however, the mold persisted on the bolts and washers even after washing.
Further investigation revealed that the issue was not rust but rather mold that had penetrated the paint on the bolts and washers. The color used on these components is distinct from the paint used on the rest of the structure and possesses a porous quality.
How does this occur?
When bolts and washers are consistently submerged in water, the paint deteriorates and absorbs moisture, leading to mold formation.
Amerimax’s product engineering offers insight:
- When aluminum alloy parts come into contact with dissimilar metals or absorbent building materials likely to be continuously or intermittently wet, the adjoining surfaces should be painted or separated according to the aluminum design manual’s guidelines. (This includes painted bolts and washers.)
As for the screws, bolts, and washers used in constructing an aluminum patio cover:
- Steel fasteners should be stainless steel (3000 series), galvanized, or double cadmium plated. Bolts should adhere to specifications such as ASTM A-307 hot-dipped, mechanically galvanized, zinc electroplated, aluminized, or 300 series stainless steel. Concrete anchor bolts are outlined in the details. Screws and bolts need to comply with specific standards.
In conclusion:
Unlike rust, mold accumulation on top of your patio cover is generally non-corrosive. Addressing this issue could involve occasionally painting the bolts and washers as part of your regular cl.
After short consideration, the black area shown above is mold. This will occur when the cover is not cleaned or maintained over time.
The customer did clean the structure after I asked him to.
After the cleaning and without further effort, the mold remained on the bolts and washers.
Upon further examination, we concluded no rust, but the mold penetrated the paint on the bolt and washer. This paint used on the bolts and washer is a different type of paint than the rest of the structure and is porous.
How does this happen?
When bolts and washers are submerged underwater continuously, the paint will break down and absorb the moisture, and mold will occur.
Here is the explanation from Amerimax product engineering.
18. Where aluminum alloy parts are in contact with dissimilar metals ( other than stainless, aluminized, or galvanized steel) or absorbent building materials likely to be continuously or intermittently wet, the fraying surfaces shall be painted or otherwise separated by the aluminum design manual part. (otherwise painted bolts and washers)
What screws, bolts, and washers are used to build an aluminum patio cover?
Engineering states:
11. Steel fasteners shall be either stainless steel (3000 series), galvanized, or double cadmium plated. Bolts shall be ASTM A-307 hot-dipped, mechanically galvanized, zinc electroplated, aluminized, or 300 series stainless steel. Concrete anchor bolts are specified in the details. All wood screws must comply with ANSI/ASME standard B18.6.1 and AWC NDS-18 12.1.5. all lag screws must comply with ANSI/ASME B18.2.1 and AWC NDS-18 12.1.4. All steel washers must be ASTM F844 W/ dimensions per ASME B18.22.1, type A. All steel nuts are to be ASTM A563. The minimum washer diameter shall be 1″ for bolted connections. Screws and bolts will have a minimum edge distance of 2X fastener diameter.
Conclusion:
It would be best not to worry about mold collecting on top of your patio cover because it is not corrosive like rust. A little paint on the bolts and washers now and then could be accomplished when you clean your patio cover regularly. All fasteners used will last forever.