Methods and compositions for inhibiting carbonyl-based fouling of basic wash systems. The methods comprise contacting the hydrocarbon stream that is or will be subjected to such washing with water soluble or water dispersible copolymers comprising repeat units of 1) ethylenically unsaturated monomers such as acrylic acid with one or more 2) other repeat units such as alkyl acrylates, allyl ethers, ethoxylated allyl repeat units, etc. In other embodiments, a third repeat unit 3) is present and may comprise a hydrophobic moiety such as a styrene repeat unit. The compositions may be terpolymers comprising repeat units 1), 2), and 3).