General A&P Practice Test

The key idea is that non-approved cleaning compounds can introduce hydrogen into metal components, making them more prone to brittle failure. Hydrogen embrittlement occurs when hydrogen atoms diffuse into the crystal lattice of certain metals under stress, reducing ductility and causing microcracks that can grow into cracks or fractures. Aircraft structures and fasteners often use high-strength steels and alloys that are especially susceptible to this effect, so cleaners that release hydrogen or promote hydrogen uptake are a real safety concern. Approved cleaning products are formulated and tested to minimize this risk, as well as to avoid other damage like unwanted corrosion. While some improper cleaners could potentially corrode aluminum or leave problematic residues, the primary and most critical risk described here is hydrogen embrittlement of metal SAMPLEstructures.