I had no issues using it on my cases, and regularly use it to degrease my rims, spokes, any chain lube residue.
http://www.zepcommercial.com/product/Industrial-Purple-Cleaner-Degreaser-ConcentrateThe Zep Commercial Industrial Purple Cleaner & Degreaser is a water-based alkaline cleaner formulated to clean heavy machinery, engine parts, construction equipment, fiberglass, unfinished concrete, masonry and asphalt. Avoid contact with painted surfaces, aluminum, brass, chrome, copper, marble, slate, granite, natural stone, wood and other alkaline sensitive surfaces as damage may occur.
Always test product in an inconspicuous area prior to use and allow to dry to determine compatibility. Directions: LIGHT SOILS: Mix 20 oz. of product with 1 gallon of hot water and spray or mop surface. TOUGH SOILS: Mix 32 oz. of product with 1 gallon of hot water. Apply to area to be cleaned with brush or pressure washer. Rinse thoroughly and allow to dry. Second applications may be required for some stains. Do not allow product to dry on surface before rinsing. -