skip to Main Content
Call Today! 714-713-2240 or 949-233-2376

Does Alumawood or Aluminum Patio Covers Rust?

Do the Alumawood or Aluminum Patio Covers Rust?

I cannot post for other manufacturers or suppliers; I can only post for Alumawood by Omni-Max or Amerimax.

Generally, most-aluminum patio cover products do not have exposed components made from raw steel. All fasteners for the exterior are galvanized, hot-dipped galvanized, mechanically galvanized, double cadmium plated, aluminized, zinc electroplated, or 300 series stainless steel.

I came across a customer complaining about rusty bolts and washers that discolored over time on top of his patio cover.

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 that there was 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 types of 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.


It would be best if you did not worry about mold collecting on top of your patio cover because the mold 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.