Surface Preparation Values And Sandblasting Economics^⋆ Available to Purchase

This paper aims to show how surface preparations can be dependably and economically determined beforehand, and the total performance value of coatings either increased or decreased, depending on service requirements. An outline of all suitable surface preparation methods will be given although the main emphasis will be on preparation by sandblasting. Metal can be sandblasted by the dry or wet process in either an open or closed system. Present limited use of proper terminology and good selective interpretation of blasting work develops costs that can range from 5c to 40c per sq. ft. There is a need for some fluctuation, but in many cases greater initial economy is possible if real needs are understood. To properly interpret such needs, distinct practical dividing lines for blast finish classifications must be found. Presently, it is said “blast the surface and prepare for paint application.” One operator interprets this as a job that can be covered at the rate of 350 ft. per hour; and another operator, at the rate of 100 ft. Because of this ambiguous meaning, many a blast job has to be done over. In other cases, a high priced job involves the. removal of all scale and binder to the white metal which requires approximately one hour blasting per 100 sq. ft., yet the coating could have performed as well with the less costly removal of mill scale only. Further value is placed on blast sand selection. Some sands produce a high initial breakdown. The ultimate production and surface quality depends largely on well selected sand. Sand grain size is also important, especially where a thin coating is contemplated. With present labor costs, equipment can mean the difference between success and failure on a job. The paper touches on the importance of equipment which will dependably help to reduce the overall cost in sandblasting.