Presto Black BST4 from Birchwood Technologies is a brush-on cold blackener for iron and non-stainless steels that is formulated to produce a durable black finish within 30 seconds.
In the aerospace industry, BST4 can be used as a fast-acting blackener for rebuilding processes on pistons, bearings, crankshafts and re-machined areas or other reworked metal parts. It also is suited for use in prototype and re-machining applications, and can serve as a manual black oxide process for simple brush-on needs.
In the machine shop, the solution can be used to blacken re-machined areas or reworked metal parts. It also is suited to quickly repair scratches or damaged areas on parts previously black oxide finished. The resulting finish has a good black color that blends well with existing black oxide finishes and will withstand the same degree of salt spray exposure as the original black oxide, the company says.