SAE - ARP4118B
(R) Isolation and Corrosion Protection of Dissimilar Materials, Carbon Composite Structure Repair
|Publication Date:||1 July 2019|
This SAE Aerospace Recommended Practice (ARP) provides methods and guidelines for isolating dissimilar repair patch materials from carbon fiber reinforced plastic (herein also referred to as carbon composite) structure during a repair operation.
These procedures are applicable to any repair procedure for carbon fiber reinforced plastic parts in which the repair patch is a metallic alloy that can form a galvanic cell with carbon in the presence of moisture or other electrolytes. The principal patch materials, discussed in terms of their relative galvanic compatibility with carbon composites, are aluminum, titanium, stainless steel, and carbon composite.
While not covered directly under this specification, reinforced plastics used in structural repairs also include parts made with fiberglass, aramid, or boron fibers. Fiberglass and aramid fiber reinforced plastics do not have galvanic reactions with other materials. The procedures outlined herein are not essential with these materials; however, the sealing procedures covered are still recommended as a means of preventing moisture entry. Rarely used boron filaments can produce a galvanic reaction by contact between the tungsten core of the fiber and adjacent metal, particularly in a bolted repair where the metal fasteners can contact cut fibers. Thus, the procedures outlined herein are advisable for bolted repairs of boron fiber reinforced plastics.
The procedures are primarily concerned with bolted repairs that introduce the highest corrosion risk due to the addition of holes and dissimilar fastener materials, but bonded repairs are also considered.
The procedures are also applicable to repairs involving reinstallation of metallic inserts into a carbon fiber reinforced plastic part.
Generic materials and parts are described with no specific vendor identifications. All materials used in the procedures outlined shall be accompanied by a Safety Data Sheet (SDS) and shall be handled in accordance with SDS instructions.
Shall be in accordance with AS5502 (1.1).