1、GM DAEWOO Auto & Technology EDS Engineering, GM DAEWOO Auto & Technology Standards FERRO TEST METHOD EDS-T-7938 ISSUED DATE: 1998. 06. 20 REVISED DATE: 2005. 08. 18 VERSION: 2 EDS-T-7938FERRO TEST METHOD PAGE: 1/2 ISSUED DATE: 1998. 06. 20 REVISED DATE: 2005. 08. 18 VERSION: 2 GM DAEWOO Auto & Techn
2、ology 1. PURPOSE This standard aims at specifying the method of checking conditions of coating on bare steel sheet surface that has passed through the pre-treatment process in the paint shop and describe specifically how to evaluate the coating condition based on presence and quantity of blue spots,
3、 which are created as a result of reaction between ferro solution and steel. 2. SCOPE All steel sheet whose bare surface is composed of Fe. Bare surfaces of MG(Zn-Ni) steel sheet and organic coated steel are made not of Fe but of Zn-Ni and organic resin and no reaction takes place between their surf
4、ace and ferro solution. As a consequence, their coating conditions cannot be identified with this test. 3. TEST APPARATUS AND REAGENT 3.1. Reagent : Ferro solution 3.2. Test apparatus: stop watch, pincette, filtering paper (: 5.6Y ), petri dish 4. TEST PIECE CONDITION & REAGENT PREPARATION 4.1. Test
5、 piece preparation 4.1.1. Chemically treated test piece that has passed through degreasing washing surface control chemical processes in the paint shop pre-treatment line 4.1.2. The test piece is constructed based on the actual body door outer panel. 4.2. Reagent preparation 4.2.1. K3Fe(CN)6: 3g 4.2
6、2. NaCl: 4g 4.2.3. FON(surface active agent): 0.7g 4.2.4. Mix the above and D.I. water to make test solution of 100g. 5. TEST PROCEDURES 5.1. Prepare a chemically treated test piece that has passed through the paint shop pre-treatment line. 5.2. Fill the petri dish with an adequate amount of ferro
7、solution to sufficiently wet the filtering paper. 5.3. Sufficiently wet the filtering paper with ferro solution. EDS-T-7938FERRO TEST METHOD PAGE: 2/2 ISSUED DATE: 1998. 06. 20 REVISED DATE: 2005. 08. 18 VERSION: 2 GM DAEWOO Auto & Technology 5.4. Put up the wetted filtering paper onto the horizonta
8、lly-laid chemically-treated test piece for 1 minute. Take care that no air film is formed between the filtering paper and chemically-treated test piece. If air films are formed, remove them by pressing with a pincette. 5.5. One minute after, remove the filtering paper with a pincette. 6. EVALUATION
9、6.1. Observe the surface of the chemically-treated test piece which has been covered with filtering paper for presence of blue spots. 6.2. Evaluation standard No blue spots shall form. 6.3. Action If blue spots are formed on the chemically-treated test piece surface by the action of ferro solution, it means the chemical film on the metal surface is unevenly formed. To remedy it, check and adjust control parameters (F.A, T.A, temperature, acceleration rate) and ion concentration (Zn, Ni, Mn) of the chemical process.
