1、DWT FOR PUBLIC COMMENT Latest date for receipt of comments cuhnent 90/72591 Our ref ACE/44 Technical Committee ACE/44 Date ?$le i9%6. Protective treatments and finishes for aerospace purposes BRITISH STANDARD : AEROSPACE SERIES PHOSPHATE TREATMENT OF FERROUS ALLOYS (prEN 2793) This draft is now avai
2、lable for public comment and your views and technical comments on it would be appreciated. Pf you have no specific comments to make but find it generally acceptable it would be helpful if you would notify us accordingly. Suggestions entailing revision of the text should indicate the preferred wordin
3、g. Please quote the relevant clause number against any comment e The co-ordination of the requirements of this draft with those of any related standards is of particular importance and you are invited to point out any areas where this may be necessary. All comments should be sent to the Conmittee Se
4、cretary Mr A E Banyard at the LOOR address below. The comments received will be passed to the committee -concerned for their cqnsideration; no acknowledgement will wormally be sent. Requests for further copies of this draft should be sent to: Sales Administration (Drafts), BSI, Linford Wood, Milton
5、Keynes MKl4 6LE. th an addressed label, Orders not accompanied by a remittance will be subject to a delay. THIS IC A DRAFT AND MUCT NOT BE REGARDED OR USED AS A BRITISH STANDARD 2 Park Ctreet London WL4 2BS Telephone 01-629 9000 Telex 266933 BSILON G Head Office 825777 BSIMK G Sales of manganese al:
6、 havin6 a nass per uriit area within the ranke of 3 to 8 glutz of tredtea surface. The coating is usally produced by immersion types of accelerate processes (see clause 4-1 xiote i) This class will be used normally whet? a suppies;er,ir,ry finish with oil or grease is specified, or when maxirnun, co
7、rrosion protection or wear resictence is desired. It is not recnm.ended for use under paii:t, varnish cd lacquer finishes BE sheet materials less than 1,O IIUII thick due eo depth of chmical roughening. 4,3 Class C A coating consisting esSentially of phosphates of zinc ar,d having a mass per unit ar
8、ea within the range of 4 to 10 g/m2 of treated surface. This coating is usally produced by an immersion type accelerated process (see note 2) IL is generally used fcr ccrrcsior: protection under paint finishes. A class A iotiig may be sed when a class 6 cozting is called for except on thin sheet mte
9、rials (see clause 4.1). 4.4 Glass D A coztirig consisting escectially of phosphates of zinc and having 3 wss ?er unit area within the range of 1,s CO 4 g/mL of treated surface. The ccszing is usually produced by an immersion type accelerated process (see ncte 2) or by 8 spray type accelerated proces
10、s. Thio class will ncrsctally te used only for the pre-iireatment cf ehlir, steel sections or sheet materia9 under paint? varnish, or lacquer coatings of high protective value. Rote 2 : An accelerated process is one tere Lhe solution contaiais zinc phosphate phosphoric acbQ e6.d accelerating agents
11、such as nitrate nitrite, chlorate or nitroguanidine. 4,a Class E W coating consisting essentially of Fhocphtes of zinc and havinig a mss per unit area within the range of 0,2 to 1,s g/m2 of treaeed surface. This elacs wild. normlly be used where parts are to be defomed Lquriiig further fabrlcatiofi
12、ater the applicatiori f paint, vzrnish or lacquer, and for improving paint adhesfon to cadmium or zinc depc,citc (see clause 1). 5 Abbrevicitfons, symbols and units . Rm (nnax-9 : The maximur specified tersile strength. I ? Pr.fonr!ation fur the pb-ocecsor - the reference oi the subsr-:e standErd zz
13、ti Lhe mrczllurgical saee of the substrate, che rms to te processed, B the tim Er. temperetuit of ehe heat txeatric.i t-. Leiorr ;rd zfter procerring, - fhe nature of b.6 suppiecir.t.zr: finish, if require0 !e.g. oll, grezse, paint, etc.). 8 Ccr.6ition of perce prior tc :,i-ocessii:g 8.1 Geneael 8.2
14、 Stress relic: After firicl machiniris and prior t yhosphatiiig steel corpcnents siicll be 2el;rrdsed diid stress rellc-t.ed as iridicated III tzbie 1. Table 1 Stress zelief hat treatment :.esc th2L 11uo L ?b5C FPa nay be zinbritr:tl t:; phosphate taeacner;, an2 shsll ocly be trestrci if specified o
15、n the ckawing tc ethods controlled bj7 the Cesign authority. 9 Process scfieduae The process consists of the following steps : cleaning o phosphating, rinsing cliroic acid rinse if required, staining, if acquired, dry ins hydrogen ecbrittlenect re2ief heat treatLientp supplementary treztmnts. 10 Pre
16、-treatments The t:q of pre-treatment used prior to the phocplisting process d=termiues the crystal size oL che phosphatc coating, A fine crystal structure give5 the best corrosion prUttr (:, si-:d t,-ezr icrltcnct prEN 2793 Page 7 All pzirts ior phosphating shall he free fron; pniiit, grease, oil, s
17、cale rust or iorrign riatter. Clcsiiiiig by r;o!vc:nt degrezsing is grricrul ly suff icieiit ior steels Kith a in2chii:td SUXCC but where the siir:ce is covered vith hczt treatment scale, so1ver.t degreasing icllowed b: abrasive b2.sting is tc, be preferred. hihere acid or alksli c1eaxiir.g is selec
18、ted clicri the paies shall subsequently Le . Parts which have been surface hardened e.g. by carburizing shall not be heated create6 above 140C ur-less otherwise agreed by the desigr; cuthority. For parts with soldered join: tlie tmperature sholl be re:;Cric:ed to 13CC. PX-KS made from steel of REI (
19、ma:.) 1450 MPa are subject to l:e control of the design authority. Prior to the de-ernbrittieniect Ereatmen2 it must be ecsured that iiil traces OP maskirig, if any3 have been removed ac that the parts are in a clear. condition. 12.4 Supplenentary finishes After rins;ng9 drying 2nd the baking trztre
20、nt chere appiled md withiti 8 hours ehe p5ospliate coating shall be provided wich a supplrwitary firiish. The type of finish required (e.g. oil, grease, paint, etc.)$ and in the case of paint, varnish or lacquer9 the weight GT thickness of the cnating, shall be as stipulisted on the drawing or order
21、. Should surface creatment of the parts wich paiolt, varnish or lacquer witlibn hours be in?poscille, the phocphGzed parta shall be kept under conditions which preciucie coIicarlri;it!.or or cdectioi of coisturc ;n the surface. 13 Renoval of the coating Any supplenientary finish applied shall first
22、be removed by a suitable meacs, e,g. creatment by organic solvent, alkaline, etc. O abrasive blstings Phosphate coatings shalh be removed by either grit binstlrig 01: treatniect iii a stripping solution, ictiibited te prevent Uczcceptehlc attack on rhe basis etzl. hinisdiatedy cfter zernoval of the
23、defective phosyhace coatiiig the parts should 5e re-phosphated ir, ccordancc with clause 11. Suitah; e stripping soluticjiis for removing phosphatt? cooeii ta re biteri in arms:; E.3. The stripping solutions dc not embrittli high strength steelso vr?d are recornended for use on screls with c specifi
24、ed maxiauni tenrille strenett: Rxn (max;.) 11CG I.:Fz., Iiirrr rrloi-al of the phosphate coatings, the perts sbii be clioroughly wzbheL Co renove en:? stripping so1utiGr rcsiduec bcLoie re-phosFlat ing o 14 We qu i red cti a 1- a c t e r Is t i c s The phosphate coatifig shaJl be uniform, fine grain
25、ed an satt in appezrance. Thers shall be n uritreted patches or flaky an6 uneven deposits on the treted surfaces a PhosphaLe coazings shcb-iiig ina- vaiations ip colour or surface texture, due to previous surface trzatments, heat treatment or C:SSS h or F coatiqs tLt: czi-eful uppJ.cotioii of one or
26、 more of the flliit; test:. ciiall be applbc-8 : - scl-zpe the surface once with t aiJ.ur.t knife. Ccatsd surfeces show a whitish streak e 4 - scrape a small area xfth.a sharp knife, Coated surfaces yield a 19ght grey powder Parrs r;hich undergo an9 comply with these tests may be given the agpropria
27、ce finishing treatment and subnitted with th remainink parzs of ehe b36ch subject to rie agreement of the qualfry assuraice authoriej-. 15.1.3 FreeaoE irom corrosive residues Phosphated arid sealed components shall be subjected to the rest described beiors cofdil-i efficiency oi the bcshing procedur
28、e used. Suspend she part for 7 days at a temperaeure o% 15 eo 25C in a closed vessel 5s t:tiIcli the atmosphere is krpt humid by i: layer of wateer in ehe bozrom of the vesseS. At the cad of t-liis period, remcede ehe port and inspesz ir immdltely for signs of rust or bliseering of the point film. T
29、his test shabi te perfromed bs a process crxtrol check rattier than batch release tese. 15.1.4 Cozting weight The coating veight shill te determiniea ai a part according to :ir.ex 5 aicr phospliating, rinsir,g and dryicg but bei iizve giver, satisfactory results, Parts zrorn the scme batch of uhicii
30、 ybzts railed and Subsequent batches s;l:ll be re-treated (see clase 1 1) pruviding ehe dlnieiicioris have not beer. affected. 17 Gesignation The desigcation gives the reference cf this stadsrd and the class ci the coating : 8 EN 2793 Class P. Number of standard _ Class of ccating Araex k Advice on
31、phosphaciiig OP tiif,h strengtl: steel A,l bt is emphasized tliat the use of acid solutions tu emove nst srid liectt treutrneiit scale before phosphate treament may be :he cauce of rlit: Itornation of unacceptable corse crystalline phosphate coatiribs which may allow light rusting CO occur during su
32、bsequent afiislng ar?d drying upersilor. e The qualie:. 02 the phosphate coating rr,ey be improved by brusiibiig the suriace of Lhe metal before phosp:rthocis. e,g. abrasive blasting, is pireferea. SOL gceniig to EN 2409 may 3e foucd beneficil to avolG tress-corrosio. A.2 In the cace O certain low a
33、lloy steels; e.g. 3 chromius-.molpbdenu.- vamd ium acd copper-s il icone-molybd enum-virticd ium s tee Is the bec E ptcsp ha 6 e coatings 2re obtained using accelereted solut iocs Considerable difficulties have been met in 0bteir:irig acceptable phocphete coatings on the former type of steel particu
34、larly in ehe forgeci iorrr. aril It nay be necessary to consider on alternative mechod of protection. A-3 The free acid concentratii11) CJL the pkocplizte solution can Eorkedly ffect she quality of the phosphate mating of alloy steels I e g a 2,5R r.icl:el-chroLiun- molybd enum and maraging (nickel-
35、coba1 t-nolybdrr.us-c itaii iui!l) tylt: t. te el-, It is rec.t=.l;dei3 th2t the pcltzge t Lhe free acid ratic be maintained i;t not less ehzin 6 bo 1 to obtsn acceptobie cobings and preier.t uczccc;t,h:e attack andlor pietixg of the steel luriti6 the phosphate tirecitmenl;. The free acid level of t
36、he phosphtr process solution, which tefitis to increase when the bath Is iic,$ used Cut :i12i?teir.r6 :errture, c;c Uc decreased by treatment wich clean steel crap or steel wool, Annex i3 B.1 Kornal method B.1.1 Stripping solution : 102 chromic acid (CrO,) in water, used at 65 - 90C. b.1.2 A comenie
37、nt surface area for determinaticr. of CoatiiiE weight is etout 100 cyi12. Weifh the pars and immerse it in an unused sample cf z solutiori picpared as above aiu allow it tG remin in the solutioil ur,til the coaLing had ditisolvsd (a period of 5 minutes is noraz&;:y sufficient). Renote the part fror,
38、 the solutior., wash for 30 seconds in runnizg water and ubpe OLL ai: nor-adherent niztier with a wet rxab of otfoil wool, Dry thorugtily and rs-weigh. 3 2 roc e d u r e e - B.1*3 Ca Iculat ion The weight of phosphate coating (g/n2j = - w A ri where W = loss in weight of Lhe pirt in grass aiad ti =
39、surface area in square netero. B.2 Alternative ethod B.2.1 Stripping solution Inhibited sulphuric acid : dissolve 0,05 g of di-o-telylthiourea in 100 1 of suphuric acid (p 20“ = !,a4 g/cmj. B.2.2.1 Dissolve the phochste ccjat-i-t fror: B hr.cbn ;frez of the pcrc. The soiuriori may be coveieutiy resc
40、ricted to a kncr:i; urea by cciltaining i: iii an open ended glass of poiythene tube stuck 0x1 to the unsealeter, as described above, chis forrnuic reduces 20 : V 5.3 Stripping solutions Lor rertoval cf phcsphate ctigs The stripping colutiuns are given in table 3. Table a Base Ersel Ferrous alloys Ziwe CZ8E:iuim $F Composition of Operating stripping solutior, I temperature C i IIkl?ik:SiOL tisne minutes !detal removal rate In 10 minutes g/m I l I I ! 90 5 l ?O I 5 I = 0;1 I I 4% triethmolamin 1Lk Na EDTA 2: 92 kaQE 75: E o s- - I 1 I 2
