Development of a NMP-free paint stripper

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Our industrial partner, GreenSolv, is marketing a paint stripper, the AeroStrip 274WL, which contains N-Methyl-2-Pyrrolidone (NMP). It is used to remove paint coatings from metallic pieces so that they could be refurbished and reused. However, NMP (CAS 872-50-4) is almost banned in Europe and frowned upon in California. Large corporations such as the US Navy, Bombardier, Pratt & Whitney, Boeing & others are looking for a NMP-free paint stripper that could be as effective as the AeroStrip 274WL. The objective of this project is to make a new product, the AeroStrip 294WL, a NMP-free paint stripper. In a series of test performed by Scientific Material International, Inc (SMI) in Florida, in accordance with MIL-PRF-83936C (USAF) for aircraft wheels, landing gear components and other aircraft and support equipment, it was shown that the AeroStrip 294WL was causing excessive corrosion and hydrogen embrittlement on metallic pieces made of aluminium, magnesium and steel. Clearly, the current version of the AeroStrip 294WL is not acceptable for the aerospace industry. It is critical to understand the role NMP is playing in the formulation of the AeroStrip 274WL. NMP plays a determining role in removing paint coatings, by penetrating the layers of paint and breaking the bond between the paint and the object by swelling the paint. However, NMP is also playing a critical role in retarding/preventing corrosion and hydrogen embrittlement in metallic pieces. It is critical to understand the link between NMP and the corrosion and hydrogen embrittlement of metallic pieces, and how to remediate to this unexpected effect of the absence of NMP in the AeroStrip 294WL. This project will address these issues through a detailed evaluation of the role played by NMP, solution pH and solution alkalinity in the hydrogen embrittlement of metal coupons such as cadmium coated steel, aluminium and magnesium.