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CLINIC PARTS CLEANING Military Specification Approval Q. We are a manufacturer of pretreatment chemicals with a large focus on the automotive industry, and we would like to get our product approved on some Mil Specs. Who or what government department handles this?— M.M. A. The Department of Defense has a Qualified Product Listing (QPL) for each of its specifications. I have not personally been through the process, so am not familiar with the amount of red tape and bureaucracy associated with this sort of program. This website provides a comprehensive start for understanding the existing QPL, with information on specifications, the approval process and contacts to initiate the supplier process: dscc.dla.mil/ offices/sourcing_and_qualification. If you are an existing supplier to the automotive industry, I assume you already know and understand this, but obtaining additional qualifications to military standards will do little or nothing to improve your market. Most companies in the automotive sector generally defer to existing specifications within several of the automotive OEMs. Additionally, there are a number of other standards agencies such as ASTM, ISO and especially SAE that provide much of the supporting specifications used in the automotive industry. If you are planning to expand your business into other areas within the United States, the approval to the military standards could be beneficial, but this should be weighed against the added costs and work necessary to gain these approvals. Incoming Rust Inhibitors Q. We have a five-stage wash system using an alkaline cleaning package. Some of the rust inhibitors coming in on parts are not water-soluble. Should they be?—H.S. A. Rust inhibitors can come in a variety of types and efficiencies. In general, water-based rust inhibitors are only applied where short-term, indoor rust protection is required. These will often be used in manufacturing plants that have a relatively short work-in-process time of a few days. If you are shipping significant distances over several days in addition to the in-process storage time, and there is possible exposure to the elements during transit, it may be that a water-based rust inhibitor will not provide effective protection. In that case, a light, oil-based rust preventative should be used. This category of rust preventative, which is somewhat similar to WD-40, often utilizes a water-displacing additive in a solvent base. The rust preventatives in the third category are actually oil-based and also incorporate water-displacing additives. Its advantage is that the water-displacing additive will orient and be adsorbed by the steel surface, while the oil base provides added corrosion protection. As would be expected, this last category of rust preventative is the most difficult to remove from the part, especially with extended storage times and elevated temperatures. 36 DECEMBER 2013 — pfonline.com pfonline.com/experts There are a number of different types of corrosion inhibitors available for industrial use. The more effective a rust inhibitor, the more tenacious it will be to remove from the steel surface. So when you ask if your customers should be using a water-based inhibitor, the answer depends on the degree of rust inhibition they require. Based on the previous explanation of rust inhibitors, you may believe that the customers DAVID S. PETERSON / Consultant are applying a rust partscleaning@pfonline.com inhibitor that is excessive for the situation. If that is the case, you may want to initiate a dialogue with them on their rust-inhibitor requirements and how this is affecting your processing of their parts. It may be possible that this conversation could result in potential time and cost savings to you and benefit to your customers. Ultrasonic Rust Removal Q. What ultrasonic frequency is best for removing corrosion on stainless steel?—O.T. A. Most often, rust removal is accomplished with the use of an acid cleaner or, occasionally, strong alkaline cleaners. Generally, ultrasonics alone in a simple medium of water would not be sufficient to remove most rust deposits. Ultrasonic solutions are more effective when used after they have been "degassed" which involves boiling or heating the solution above the operating temperature of the bath. This is because the dissolved gases in a bath can lower the effectiveness of the ulatrosonic cavitations. Based on this, I would not recommend the use of an ultrasonic bath if you are using an acid cleaner to remove the rust residues. The acid cleaner will generate a certain amount of hydrogen gas at the part surface that would decrease the efficiency of the ultrasonic process. An alkaline cleaning process would not have the same surface reactions, so you would find the use of ultrasonics more effective. If using ultrasonics to provide a boost to the rust removal process, I would expect a lower frequency to have more energy to remove some of the rust. I would recommend a frequency in the range of 20-40 kHz. Electrocleaning Q. We have a barrel alkaline zinc plater and have had problems with cleaning in the low-current areas. Our