Chemical milling maskant application process

A process for applying a volatile liquid maskant to an article to be subjected to chemical milling, the process including the steps:

• (a) providing a controlled temperature bath of said volatile maskant characterized as fast drying, providing a vapor blanket overlying the bath, and also maintaining the temperature of the vapor blanket at less than the bath temperature,
• (b) placing the article into position above the level of the bath and blanket, and adjusting the temperature of the article in relation to the bath temperature, so that the temperature of the article surface is about 70.degree. F. which is about 4.degree. F. less than the bath temperature, prior to lowering of the article through the vapor blanket, and prior to contact of the article with the bath,
• (c) lowering the article through the blanket into the bath, and withdrawing the article upwardly from the bath and through the blanket at a controlled rate between 12 and 26 inches per minute characterized in that the maskant coats the article to controlled coat thickness, and also in that the bath remains substantially free of return drainage of maskant off the withdrawn article,
• (d) and, following said upward withdrawal, flowing a gas stream into contact with the maskant coat while the article remains above the level of the bath to assist in rapid drying of the maskant, the maskant coating having a thickness within the range of about 4 to 12 mils,
• (e) the maskant consisting essentially of a volatile hydrocarbon solvent, and solids including elastomeric material, phenolic resin, and filler dissolved in the solvent, a major volumetric proportion of the solvent consisting of methylene chloride.